How Physicians Diagnose Urinary Tract Infections: The Potential Influence of Laboratory Regulations on Test Availability and Use

Busy clinicians have come to rely on the office laboratory as an important tool in providing timely, efficient, and high-quality patient care. However, concerns have been raised about poor accuracy in physician office laboratories and financial incentives that encourage overuse of tests.^1-7 Recent studies have documented inaccurate office laboratory testing.^8,9 Previously, the Commission on Office Laboratory Accreditation concluded that approximately 5% of office laboratories have serious deficiencies involving quality control, instrument maintenance, specimen management, and proficiency testing.¹⁰ Similar concerns led to the passage of the Clinical Laboratory Improvement Act of 1988 (CLIA-88), which was implemented in the fall of 1994.¹¹ Before CLIA-88, physician office laboratory quality regulations were decided at the state level.¹² Both state and federal regulations require adherence to specific measures (eg, proficiency testing, quality control, and quality assurance) to operate an office laboratory.

The critics of quality regulations assert that the measures might actually decrease the quality of care. They note that the regulations impose a fixed cost on the physician’s practice that must be spent regardless of how busy the laboratory is. The additional costs of compliance could discourage physicians from offering tests that would otherwise be done.^13,14 This reduction in test availability might occur in both high- and low-quality laboratories. Therefore, regulations aimed at improving quality might have the unintended effect of reducing the availability and use of clinically beneficial laboratory tests, thereby decreasing the overall potential benefit of the regulations.

We previously surveyed primary care physicians about their clinical approach to patients with a possible uncomplicated urinary tract infection (UTI).¹⁵ That 1994-1995 survey included primary care physicians in 4 states and contained detailed information on their work settings and clinical behavior concerning cases of UTI. In this paper we use those survey results to examine the potential effects of office laboratory quality regulations and test availability on testing for UTIs. This is possible because one of the states surveyed, Pennsylvania, has had statewide physician office laboratory quality regulations similar to CLIA-88 in place since the mid-1970s.^12,16 All office laboratories in Pennsylvania were required to register with the state, have a written procedure manual, perform quality and proficiency testing, and comply with state regulations, regardless of the level of testing.¹⁶ Office laboratories in the other 3 states were not regulated until the implementation of CLIA-88 in late 1994. Thus, the survey includes 1 regulated state and 3 states that were just beginning to be regulated. This should provide a conservative estimate of the differences between a regulated and a nonregulated situation, since some of the physicians in the previously unregulated states may already have adjusted to CLIA-88 when our survey was done. The adjustment to CLIA-88 did not occur instantaneously; laboratories have continued to move toward a higher percentage of waived and provider-performed microscopy laboratories (from 57.8% of all laboratories in 1995 to 75% in July 2000) since CLIA-88 was implemented.¹⁷ We sought to determine if office laboratory testing capabilities or availability differs by state and if self-reported use of the tests in diagnosing an uncomplicated UTI is related to the availability of the tests.

Methods

We examined the results of an 88-item survey concerning each physician’s clinical approach to patients with a possible UTI. We mailed the survey in 1994 and 1995 to practicing primary care physicians in 4 specialties that commonly treat adults with uncomplicated UTIs: general internal medicine, family practice, obstetrics and gynecology, and emergency medicine. The emergency medicine physicians were excluded from this analysis, since most of these physicians are hospital based and do not have an office laboratory in the same sense as the other specialties. To obtain a geographically diverse sample, we surveyed physicians from 4 states: Alabama, Nebraska, Minnesota, and Pennsylvania. The names and addresses of potential respondents were obtained from the physician masterfile of the American Medical Association (AMA). Since the AMA masterfile has limited data on physician characteristics (eg, the physician’s specialty), all data in our analysis were based on self-reported survey results. We surveyed the entire population of eligible physicians in each state except Pennsylvania; a random sample was chosen from Pennsylvania because of the large number of practicing physicians in that state.

The survey asked detailed questions about each physician’s clinical approach to a 30-year-old woman with dysuria, a presentation suggestive but not diagnostic of a UTI.^18,19 The main outcomes included whether specific tests (urine dipstick, microscopic urinalysis [UA], wet prep, and urine culture) were available in the office and whether these tests were used when diagnosing a UTI in the given patient. In both parts of the analysis we controlled for possible confounding variables. These included items reflecting the physician’s belief in the usefulness of clinical and laboratory information in diagnosing UTIs and physician and practice characteristics. The variables used in the analyses are shown in Table 1.

In the first part of the analysis we determined whether practicing in a regulated state (Pennsylvania) is associated with changes in the likelihood of having tests available in the office. The 4 outcome variables in this part of the analysis included the presence or absence of the dipstick, microscopic UA, wet prep, and urine culture. Thus, test availability was analyzed using binary dependent variables (yes=the physician reported the test in the office; no=otherwise). We did multivariate logistic regressions because of the binary nature of the dependent variables. Variables explaining the presence or absence of the test in the office included the key variable of interest: the physician’s state of residence (either in Pennsylvania or 1 of the previously unregulated states) and the group of variables reflecting the clinical beliefs concerning history, physical examination, and test usefulness in diagnosing UTI in our hypothetical patient, as well as physician, practice, and community characteristics. The explanatory variables were included in the regression models to control for any factors that might confound the effects of being from Pennsylvania. We hypothesized that tests would be found less frequently in Pennsylvania when controlling for other factors.

In the second part of the analysis, we examined whether the availability of tests in the office is related to their use in diagnosing UTIs in the hypothetical patient. The outcome variables in the second part were the self-reported frequency of ordering microscopic UA, urine culture, and the urine dipstick test (the leukocyte esterase and/or the nitrite test). Test use was analyzed as a binary variable (yes=the physician sometimes or usually performed the test; no=the physician rarely did the test). We did not have information on the physician’s use of the wet prep test, so we could not analyze the relationship between availablity and use for the wet prep. Because we analyzed the variable representing test use as a binary variable, we also used logistic regression for the analysis in the second part. In each regression, the variables explaining the frequency of using the test included 3 outcome measures from the first part of the analysis (whether the dipstick, micro UA, or culture was available in the office), and the same control variables reflecting physician beliefs and the personal and practice characteristics used in the first part of the analysis. We hypothesized that test availability would be related to its use in diagnosing UTIs after controlling for other relevant factors.

We used the Stata statistical software program²⁰ for the analysis.

Results

A total of 8942 surveys were sent out. There were 2172 usable surveys returned. After excluding the responses from the 274 emergency medicine physicians, we analyzed the remaining 1898 responses. We were able to compare respondents and nonrespondents on 3 demographic characteristics: sex, board-certification status, and length of time since graduating from medical school. The survey responders were more likely to be board certified but otherwise were similar to nonrespondents Table 2. Comparison of response patterns in Pennsylvania and the other 3 states using logistic regression indicates that Pennsylvania respondents were less likely to be men than respondents from other states. The magnitude of these differences, however, appears small.

Analysis of Test Availability

The reported prevalence of the various diagnostic tests in office laboratories is shown in Table 3. The dipstick is the most common test; more than 90% of respondents reported having it in their offices. The culture was the least available test, and the prevalence of both the microscopic UA and wet prep were intermediate between the culture and the dipstick. Simple unadjusted comparisons indicate that for each test physicians’ offices in Pennsylvania were less likely to report that they have the test available than were physicians in the unregulated states (P <.0001).

Table 4 shows the determinants of test availability from the multivariate logistic regressions. After controlling for possibly confounding factors, physicians from Pennsylvania were much less likely to have each of the tests in the office. The odds ratios (ORs) range from 0.20 (for the microscopic UA) to 0.35 (for the dipstick). Each of these results is statistically significant.

A number of control variables were significantly related to test availability.* Important findings include the effects of the physician’s specialty, clinical beliefs, and the estimated number of patients with dysuria seen per week. General internal medicine physicians were less likely than family practitioners to have each of the tests in the office (OR = 0.14, 0.60, 0.35, 0.57 for the dipstick, micro UA, wet prep, and culture; all P values <.05), while obstetrician-gynecologists were significantly less likely than family practitioners to have a dipstick, micro UA, and culture (OR = 0.14, 0.24, 0.44; all P values <.05) but more likely to have a wet prep available (OR=5.46; P=.0001). Increased belief in the importance of the leukocyte eserase test for diagnosing UTIs was associated with an increase in dipstick availability (OR=3.40; P=.0001), and increased belief in the importance of the microscopic white cell and red cell readings for diagnosing UTIs was associated with an increase in micro UA availability (OR = 1.95, 1.83; P = .01, .001, respectively). Seeing an additional patient per week with dysuria was associated with an increased availability for the dipstick (OR=1.12; P=.04), micro UA (OR=1.06; P=.01), and wet prep (OR=1.06; P=.02).

The overall explanatory power of these models was fairly good. The C-statistic, representing the area under the receiver operating characteristic curve, ranged from 0.75 for the urine culture to 0.93 for the dipstick (a C-statistic of 0.5 indicates that the model is no better than random chance at predicting the outcome, while a C-statistic of 1 indicates perfect discriminating ability).

Test Availability and the Diagnostic Approach

The relationship between test availability and use demonstrates that the availability of some tests is associated with an increase in their use, while sometimes the availability of tests is associated with an increase or decrease in the use of other tests Table 5. That is, tests will sometimes substitute for or complement other tests when diagnosing UTIs. Physicians with a microscopic UA in the office were more likely to report ordering a microscopic UA. The presence of the urine culture increased microscopic UA use, but the dipstick, when available, appeared to substitute for the microscopic UA.

The reported frequency of ordering urine cultures was increased by the availability of a culture but was decreased when respondents reported having a microscopic UA or dipstick available.

The dipstick was the only test for which use was not significantly related to the presence of any of the diagnostic tests; the availability of the dipstick appears to increase its use, but this relationship was not significant.

Even though test availability is often related to use, the physician may not be the person actually doing the tests. Of the 1492 physicians who report sometimes or usually ordering microscopic UAs, 363 do the procedure themselves, and 803 use ancillary personnel in their office. The remainder (326) have the procedure done outside the office. In contrast, only 25 of the physicians who report sometimes or usually ordering a urine culture do the test themselves. Three hundred forty-two use ancillary help in the office, and 243 have the culture done at an outside laboratory.

Several physician and practice characteristics were significantly related to the frequency of ordering each of the diagnostic tests. Being an obstetrician-gynecologist relative to family practitioner decreased microscopic UA use (OR=0.41; P=.0001), while a greater belief in the value of the leukocyte esterase test decreased microscopic UA use (OR=0.70; P=.01), and greater belief in the microscopic white cell reading increased use of the microscopic UA (OR=3.12; P=.0001). Increased use of urine cultures was associated with being in a city with a population greater than 100,000 relative to a town of less than 10,000 (OR=1.54; P=.02) and being a government employee relative to being in private practice (OR=9.31; P=.0001), while culture use was decreased in practice sizes of more than 25 physicians relative to being in solo practice (OR=0.39; P=.004). The dipstick was used more commonly when physicians had a greater belief in the value of the leukocyte esterase (OR=5.15; P=.0001) and nitrite (OR=2.68; P=.0001) results. Interestingly, the physician’s specialty was generally not significantly related to test use (apart from the difference between obstetrician-gynecologists and family practitioners in micro UA use), in contrast to the consistent specialty differences found for test availability.

The overall power of each of these models to explain the frequency of test use was moderately good. The C-statistics ranged from 0.69 for ordering a urine culture to 0.82 for ordering the dipstick.

Discussion

This study has 2 main findings. First, for each of the office laboratory tests examined, we found significant differences in test availability between unregulated states and Pennsylvania, a state with a long-standing physician office laboratory regulatory system. The overall pattern is one of diminished test availability in Pennsylvania, after controlling for other explanatory influences. This finding was present for every test we examined, regardless of the cost of performing the test or the level at which it was regulated. This supports the hypothesis that tests are available less often in a regulated state.

The second main finding is that the physician’s diagnostic approach to UTIs was related to the in-office availability of tests. This finding supports our second hypothesis. However, the relationship between test and availability and use was more complex than suspected. Not only was the self-reported use of some tests (microscopic UA and culture) related to their availability, sometimes the availability of a test was associated with a change in the self-reported frequency of using other tests. Thus, some tests appear to substitute for others (availability of the dipstick reduces use of microscopic UAs and cultures, and availability of the microscopic UA decreases culture ordering), while the availability of the culture was associated with increased use of the microscopic UA. We also found significant relationships between the physician’s belief in the usefulness of test results in diagnosing UTI with both the availability and subsequent use of the diagnostic tests.

The multivariate analyses indicated that physician and practice characteristics were related to the availability and use of diagnostic tests. This finding is consistent with previous studies reporting numerous factors influencing the use of laboratory tests.^21-23 To our knowledge, the association between physician belief in the value of the test in diagnosing a condition and test availability and use has not been documented previously. Thus, the influence of quality regulations on test prevalence and use will be modulated by the configuration of these other factors.

This study differs from previous studies on laboratory use in that we have been able to control for many relevant explanatory variables, including the physician’s belief in the diagnostic importance of elements from the patient’s history, physical examination, and test results. Many of these items add significant predictive power in a “logical” direction. For example, the availability of many tests was related to the physician’s belief in the value of the results provided by that test, and these beliefs were related to the physician’s diagnostic approach. Although it is not possible to tell from the survey if the physician’s belief in the usefulness of the test is causally related to the availability of a test, the results indicate the need to control for physician-specific opinions and beliefs when examining laboratory test use.

It is not possible to determine the net effect of quality regulations on patient welfare from this study. In theory, a reduction in test availability and subsequent use of a less accurate diagnostic approach is offset by higher quality and accuracy in those offices still offering tests.²⁴ We did not measure the quality or accuracy of the physician’s laboratory testing. To the extent that poor-quality laboratories are closed, regulations should improve overall welfare. Alternatively, if the reduction in test availability occurs in both good- and bad-quality laboratories, then the net effects on patient outcomes may be negative. A recent cost-effectiveness study of tests used to diagnose UTIs²⁵ indicated that the microscopic UA was reasonably cost-effective ($2964 per quality-adjusted life month), but the low sensitivity of the dipstick resulted in a poor cost-effectiveness ratio ($48,460 per quality-adjusted life month). Thus, to the extent that the highly prevalent dipstick is substituting for more cost-effective tests, as our results suggest, regulations might lead to less cost-effective care.

Our analysis suggests that changing the availability of tests may change physicians’ diagnostic approaches in ways that are difficult to predict a priori. For example, reducing the availability of the microscopic UA might lead to greater use of the more expensive urine culture. When many tests are reduced in availability, it is difficult to anticipate how the care of patients will change, since tests will substitute for or complement the use of other tests in ways that are difficult to predict.

Limitations

This study has several limitations. First, it is based on survey data that may not reflect actual behavior. However, the results are plausible, internally consistent, and consistent with previous research findings documenting substantial variation in practice patterns in managing UTIs.²⁶ Our focus on how physicians treat an uncomplicated basic UTI limits the possibility of eliciting responses based on unmeasured patient characteristics. Second, the overall response rate was low, which might raise concerns that the respondents represent an atypical or biased group of physicians. A comparison of respondents and nonrespondents along the 3 characteristics we had access to did not reveal any striking differences. And, when compared with nationwide physician work force statistics collected by the AMA in 1994, the physicians in this study had similar hours per week spent in patient care (46.2 in our survey vs 48.2 in the AMA survey) and estimated level of capitation (19.3% in our survey vs 16.7% in the AMA survey).²⁷ The estimated volume of patients with UTI was also similar to previous surveys of primary care physicians (approximately 6 per week).²⁶ Thus, the respondents in this survey do not seem to represent an atypical or unusual group of physicians. Other limitations include the fact that physicians responding to the survey might not be responsible for deciding whether to acquire or maintain tests in the office. Likewise, the survey does not contain information on other factors in the physician’s local market that might influence the supply or demand for office tests. These effects, however, would have to be quite large and disproportionately affect Pennsylvania respondents to confound our findings.

Finally, since the analysis is based on cross-sectional data, the results do not give any indication of how rapidly in-office testing declines after the implementation of quality regulations. However, as mentioned before, statistics indicate that the mix of tests in physicians’ offices has continued to move towards simpler tests since CLIA-88 was implemented. Our study provides a snapshot of the circumstances as CLIA-88 was first implemented; it would be worthwhile to assess changes in test prevalence and use in our survey population over the last several years. It may be the case that other changes underway in health care delivery (eg, improving technology, vertical and horizontal integration of physician groups, and growth of managed care) may hasten or reverse the changes in office laboratory availability implied in this study.

Conclusions

The availability of common office tests used in the diagnosis of UTI appears to be related to many factors, including the presence of office laboratory regulations. Lower availability of tests, in turn, was associated with the diagnostic approach when treating patients with a possible UTI. The net effects on patient welfare are difficult to predict, but our findings raise a serious concern about the possibility of a detrimental overall effect on patient welfare. Determining the full effect of quality regulations will require careful study to measure the changes in treatment patterns, treatment quality, and patient outcomes subsequent to the implementation of increased levels of regulation.

Acknowledgments

This research was funded by the Department of Internal Medicine at the University of Nebraska Medical Center, Omaha, and by the Department of Internal Medicine at Abington Memorial Hospital, Philadelphia, Pennsylvania.

Busy clinicians have come to rely on the office laboratory as an important tool in providing timely, efficient, and high-quality patient care. However, concerns have been raised about poor accuracy in physician office laboratories and financial incentives that encourage overuse of tests.^1-7 Recent studies have documented inaccurate office laboratory testing.^8,9 Previously, the Commission on Office Laboratory Accreditation concluded that approximately 5% of office laboratories have serious deficiencies involving quality control, instrument maintenance, specimen management, and proficiency testing.¹⁰ Similar concerns led to the passage of the Clinical Laboratory Improvement Act of 1988 (CLIA-88), which was implemented in the fall of 1994.¹¹ Before CLIA-88, physician office laboratory quality regulations were decided at the state level.¹² Both state and federal regulations require adherence to specific measures (eg, proficiency testing, quality control, and quality assurance) to operate an office laboratory.

The critics of quality regulations assert that the measures might actually decrease the quality of care. They note that the regulations impose a fixed cost on the physician’s practice that must be spent regardless of how busy the laboratory is. The additional costs of compliance could discourage physicians from offering tests that would otherwise be done.^13,14 This reduction in test availability might occur in both high- and low-quality laboratories. Therefore, regulations aimed at improving quality might have the unintended effect of reducing the availability and use of clinically beneficial laboratory tests, thereby decreasing the overall potential benefit of the regulations.

We previously surveyed primary care physicians about their clinical approach to patients with a possible uncomplicated urinary tract infection (UTI).¹⁵ That 1994-1995 survey included primary care physicians in 4 states and contained detailed information on their work settings and clinical behavior concerning cases of UTI. In this paper we use those survey results to examine the potential effects of office laboratory quality regulations and test availability on testing for UTIs. This is possible because one of the states surveyed, Pennsylvania, has had statewide physician office laboratory quality regulations similar to CLIA-88 in place since the mid-1970s.^12,16 All office laboratories in Pennsylvania were required to register with the state, have a written procedure manual, perform quality and proficiency testing, and comply with state regulations, regardless of the level of testing.¹⁶ Office laboratories in the other 3 states were not regulated until the implementation of CLIA-88 in late 1994. Thus, the survey includes 1 regulated state and 3 states that were just beginning to be regulated. This should provide a conservative estimate of the differences between a regulated and a nonregulated situation, since some of the physicians in the previously unregulated states may already have adjusted to CLIA-88 when our survey was done. The adjustment to CLIA-88 did not occur instantaneously; laboratories have continued to move toward a higher percentage of waived and provider-performed microscopy laboratories (from 57.8% of all laboratories in 1995 to 75% in July 2000) since CLIA-88 was implemented.¹⁷ We sought to determine if office laboratory testing capabilities or availability differs by state and if self-reported use of the tests in diagnosing an uncomplicated UTI is related to the availability of the tests.

Methods

We examined the results of an 88-item survey concerning each physician’s clinical approach to patients with a possible UTI. We mailed the survey in 1994 and 1995 to practicing primary care physicians in 4 specialties that commonly treat adults with uncomplicated UTIs: general internal medicine, family practice, obstetrics and gynecology, and emergency medicine. The emergency medicine physicians were excluded from this analysis, since most of these physicians are hospital based and do not have an office laboratory in the same sense as the other specialties. To obtain a geographically diverse sample, we surveyed physicians from 4 states: Alabama, Nebraska, Minnesota, and Pennsylvania. The names and addresses of potential respondents were obtained from the physician masterfile of the American Medical Association (AMA). Since the AMA masterfile has limited data on physician characteristics (eg, the physician’s specialty), all data in our analysis were based on self-reported survey results. We surveyed the entire population of eligible physicians in each state except Pennsylvania; a random sample was chosen from Pennsylvania because of the large number of practicing physicians in that state.

The survey asked detailed questions about each physician’s clinical approach to a 30-year-old woman with dysuria, a presentation suggestive but not diagnostic of a UTI.^18,19 The main outcomes included whether specific tests (urine dipstick, microscopic urinalysis [UA], wet prep, and urine culture) were available in the office and whether these tests were used when diagnosing a UTI in the given patient. In both parts of the analysis we controlled for possible confounding variables. These included items reflecting the physician’s belief in the usefulness of clinical and laboratory information in diagnosing UTIs and physician and practice characteristics. The variables used in the analyses are shown in Table 1.

In the first part of the analysis we determined whether practicing in a regulated state (Pennsylvania) is associated with changes in the likelihood of having tests available in the office. The 4 outcome variables in this part of the analysis included the presence or absence of the dipstick, microscopic UA, wet prep, and urine culture. Thus, test availability was analyzed using binary dependent variables (yes=the physician reported the test in the office; no=otherwise). We did multivariate logistic regressions because of the binary nature of the dependent variables. Variables explaining the presence or absence of the test in the office included the key variable of interest: the physician’s state of residence (either in Pennsylvania or 1 of the previously unregulated states) and the group of variables reflecting the clinical beliefs concerning history, physical examination, and test usefulness in diagnosing UTI in our hypothetical patient, as well as physician, practice, and community characteristics. The explanatory variables were included in the regression models to control for any factors that might confound the effects of being from Pennsylvania. We hypothesized that tests would be found less frequently in Pennsylvania when controlling for other factors.

In the second part of the analysis, we examined whether the availability of tests in the office is related to their use in diagnosing UTIs in the hypothetical patient. The outcome variables in the second part were the self-reported frequency of ordering microscopic UA, urine culture, and the urine dipstick test (the leukocyte esterase and/or the nitrite test). Test use was analyzed as a binary variable (yes=the physician sometimes or usually performed the test; no=the physician rarely did the test). We did not have information on the physician’s use of the wet prep test, so we could not analyze the relationship between availablity and use for the wet prep. Because we analyzed the variable representing test use as a binary variable, we also used logistic regression for the analysis in the second part. In each regression, the variables explaining the frequency of using the test included 3 outcome measures from the first part of the analysis (whether the dipstick, micro UA, or culture was available in the office), and the same control variables reflecting physician beliefs and the personal and practice characteristics used in the first part of the analysis. We hypothesized that test availability would be related to its use in diagnosing UTIs after controlling for other relevant factors.

We used the Stata statistical software program²⁰ for the analysis.

Results

A total of 8942 surveys were sent out. There were 2172 usable surveys returned. After excluding the responses from the 274 emergency medicine physicians, we analyzed the remaining 1898 responses. We were able to compare respondents and nonrespondents on 3 demographic characteristics: sex, board-certification status, and length of time since graduating from medical school. The survey responders were more likely to be board certified but otherwise were similar to nonrespondents Table 2. Comparison of response patterns in Pennsylvania and the other 3 states using logistic regression indicates that Pennsylvania respondents were less likely to be men than respondents from other states. The magnitude of these differences, however, appears small.

Analysis of Test Availability

The reported prevalence of the various diagnostic tests in office laboratories is shown in Table 3. The dipstick is the most common test; more than 90% of respondents reported having it in their offices. The culture was the least available test, and the prevalence of both the microscopic UA and wet prep were intermediate between the culture and the dipstick. Simple unadjusted comparisons indicate that for each test physicians’ offices in Pennsylvania were less likely to report that they have the test available than were physicians in the unregulated states (P <.0001).

Table 4 shows the determinants of test availability from the multivariate logistic regressions. After controlling for possibly confounding factors, physicians from Pennsylvania were much less likely to have each of the tests in the office. The odds ratios (ORs) range from 0.20 (for the microscopic UA) to 0.35 (for the dipstick). Each of these results is statistically significant.

A number of control variables were significantly related to test availability.* Important findings include the effects of the physician’s specialty, clinical beliefs, and the estimated number of patients with dysuria seen per week. General internal medicine physicians were less likely than family practitioners to have each of the tests in the office (OR = 0.14, 0.60, 0.35, 0.57 for the dipstick, micro UA, wet prep, and culture; all P values <.05), while obstetrician-gynecologists were significantly less likely than family practitioners to have a dipstick, micro UA, and culture (OR = 0.14, 0.24, 0.44; all P values <.05) but more likely to have a wet prep available (OR=5.46; P=.0001). Increased belief in the importance of the leukocyte eserase test for diagnosing UTIs was associated with an increase in dipstick availability (OR=3.40; P=.0001), and increased belief in the importance of the microscopic white cell and red cell readings for diagnosing UTIs was associated with an increase in micro UA availability (OR = 1.95, 1.83; P = .01, .001, respectively). Seeing an additional patient per week with dysuria was associated with an increased availability for the dipstick (OR=1.12; P=.04), micro UA (OR=1.06; P=.01), and wet prep (OR=1.06; P=.02).

The overall explanatory power of these models was fairly good. The C-statistic, representing the area under the receiver operating characteristic curve, ranged from 0.75 for the urine culture to 0.93 for the dipstick (a C-statistic of 0.5 indicates that the model is no better than random chance at predicting the outcome, while a C-statistic of 1 indicates perfect discriminating ability).

Test Availability and the Diagnostic Approach

The relationship between test availability and use demonstrates that the availability of some tests is associated with an increase in their use, while sometimes the availability of tests is associated with an increase or decrease in the use of other tests Table 5. That is, tests will sometimes substitute for or complement other tests when diagnosing UTIs. Physicians with a microscopic UA in the office were more likely to report ordering a microscopic UA. The presence of the urine culture increased microscopic UA use, but the dipstick, when available, appeared to substitute for the microscopic UA.

The reported frequency of ordering urine cultures was increased by the availability of a culture but was decreased when respondents reported having a microscopic UA or dipstick available.

The dipstick was the only test for which use was not significantly related to the presence of any of the diagnostic tests; the availability of the dipstick appears to increase its use, but this relationship was not significant.

Even though test availability is often related to use, the physician may not be the person actually doing the tests. Of the 1492 physicians who report sometimes or usually ordering microscopic UAs, 363 do the procedure themselves, and 803 use ancillary personnel in their office. The remainder (326) have the procedure done outside the office. In contrast, only 25 of the physicians who report sometimes or usually ordering a urine culture do the test themselves. Three hundred forty-two use ancillary help in the office, and 243 have the culture done at an outside laboratory.

Several physician and practice characteristics were significantly related to the frequency of ordering each of the diagnostic tests. Being an obstetrician-gynecologist relative to family practitioner decreased microscopic UA use (OR=0.41; P=.0001), while a greater belief in the value of the leukocyte esterase test decreased microscopic UA use (OR=0.70; P=.01), and greater belief in the microscopic white cell reading increased use of the microscopic UA (OR=3.12; P=.0001). Increased use of urine cultures was associated with being in a city with a population greater than 100,000 relative to a town of less than 10,000 (OR=1.54; P=.02) and being a government employee relative to being in private practice (OR=9.31; P=.0001), while culture use was decreased in practice sizes of more than 25 physicians relative to being in solo practice (OR=0.39; P=.004). The dipstick was used more commonly when physicians had a greater belief in the value of the leukocyte esterase (OR=5.15; P=.0001) and nitrite (OR=2.68; P=.0001) results. Interestingly, the physician’s specialty was generally not significantly related to test use (apart from the difference between obstetrician-gynecologists and family practitioners in micro UA use), in contrast to the consistent specialty differences found for test availability.

The overall power of each of these models to explain the frequency of test use was moderately good. The C-statistics ranged from 0.69 for ordering a urine culture to 0.82 for ordering the dipstick.

Discussion

This study has 2 main findings. First, for each of the office laboratory tests examined, we found significant differences in test availability between unregulated states and Pennsylvania, a state with a long-standing physician office laboratory regulatory system. The overall pattern is one of diminished test availability in Pennsylvania, after controlling for other explanatory influences. This finding was present for every test we examined, regardless of the cost of performing the test or the level at which it was regulated. This supports the hypothesis that tests are available less often in a regulated state.

The second main finding is that the physician’s diagnostic approach to UTIs was related to the in-office availability of tests. This finding supports our second hypothesis. However, the relationship between test and availability and use was more complex than suspected. Not only was the self-reported use of some tests (microscopic UA and culture) related to their availability, sometimes the availability of a test was associated with a change in the self-reported frequency of using other tests. Thus, some tests appear to substitute for others (availability of the dipstick reduces use of microscopic UAs and cultures, and availability of the microscopic UA decreases culture ordering), while the availability of the culture was associated with increased use of the microscopic UA. We also found significant relationships between the physician’s belief in the usefulness of test results in diagnosing UTI with both the availability and subsequent use of the diagnostic tests.

The multivariate analyses indicated that physician and practice characteristics were related to the availability and use of diagnostic tests. This finding is consistent with previous studies reporting numerous factors influencing the use of laboratory tests.^21-23 To our knowledge, the association between physician belief in the value of the test in diagnosing a condition and test availability and use has not been documented previously. Thus, the influence of quality regulations on test prevalence and use will be modulated by the configuration of these other factors.

This study differs from previous studies on laboratory use in that we have been able to control for many relevant explanatory variables, including the physician’s belief in the diagnostic importance of elements from the patient’s history, physical examination, and test results. Many of these items add significant predictive power in a “logical” direction. For example, the availability of many tests was related to the physician’s belief in the value of the results provided by that test, and these beliefs were related to the physician’s diagnostic approach. Although it is not possible to tell from the survey if the physician’s belief in the usefulness of the test is causally related to the availability of a test, the results indicate the need to control for physician-specific opinions and beliefs when examining laboratory test use.

It is not possible to determine the net effect of quality regulations on patient welfare from this study. In theory, a reduction in test availability and subsequent use of a less accurate diagnostic approach is offset by higher quality and accuracy in those offices still offering tests.²⁴ We did not measure the quality or accuracy of the physician’s laboratory testing. To the extent that poor-quality laboratories are closed, regulations should improve overall welfare. Alternatively, if the reduction in test availability occurs in both good- and bad-quality laboratories, then the net effects on patient outcomes may be negative. A recent cost-effectiveness study of tests used to diagnose UTIs²⁵ indicated that the microscopic UA was reasonably cost-effective ($2964 per quality-adjusted life month), but the low sensitivity of the dipstick resulted in a poor cost-effectiveness ratio ($48,460 per quality-adjusted life month). Thus, to the extent that the highly prevalent dipstick is substituting for more cost-effective tests, as our results suggest, regulations might lead to less cost-effective care.

Our analysis suggests that changing the availability of tests may change physicians’ diagnostic approaches in ways that are difficult to predict a priori. For example, reducing the availability of the microscopic UA might lead to greater use of the more expensive urine culture. When many tests are reduced in availability, it is difficult to anticipate how the care of patients will change, since tests will substitute for or complement the use of other tests in ways that are difficult to predict.

Limitations

This study has several limitations. First, it is based on survey data that may not reflect actual behavior. However, the results are plausible, internally consistent, and consistent with previous research findings documenting substantial variation in practice patterns in managing UTIs.²⁶ Our focus on how physicians treat an uncomplicated basic UTI limits the possibility of eliciting responses based on unmeasured patient characteristics. Second, the overall response rate was low, which might raise concerns that the respondents represent an atypical or biased group of physicians. A comparison of respondents and nonrespondents along the 3 characteristics we had access to did not reveal any striking differences. And, when compared with nationwide physician work force statistics collected by the AMA in 1994, the physicians in this study had similar hours per week spent in patient care (46.2 in our survey vs 48.2 in the AMA survey) and estimated level of capitation (19.3% in our survey vs 16.7% in the AMA survey).²⁷ The estimated volume of patients with UTI was also similar to previous surveys of primary care physicians (approximately 6 per week).²⁶ Thus, the respondents in this survey do not seem to represent an atypical or unusual group of physicians. Other limitations include the fact that physicians responding to the survey might not be responsible for deciding whether to acquire or maintain tests in the office. Likewise, the survey does not contain information on other factors in the physician’s local market that might influence the supply or demand for office tests. These effects, however, would have to be quite large and disproportionately affect Pennsylvania respondents to confound our findings.

Finally, since the analysis is based on cross-sectional data, the results do not give any indication of how rapidly in-office testing declines after the implementation of quality regulations. However, as mentioned before, statistics indicate that the mix of tests in physicians’ offices has continued to move towards simpler tests since CLIA-88 was implemented. Our study provides a snapshot of the circumstances as CLIA-88 was first implemented; it would be worthwhile to assess changes in test prevalence and use in our survey population over the last several years. It may be the case that other changes underway in health care delivery (eg, improving technology, vertical and horizontal integration of physician groups, and growth of managed care) may hasten or reverse the changes in office laboratory availability implied in this study.

Conclusions

The availability of common office tests used in the diagnosis of UTI appears to be related to many factors, including the presence of office laboratory regulations. Lower availability of tests, in turn, was associated with the diagnostic approach when treating patients with a possible UTI. The net effects on patient welfare are difficult to predict, but our findings raise a serious concern about the possibility of a detrimental overall effect on patient welfare. Determining the full effect of quality regulations will require careful study to measure the changes in treatment patterns, treatment quality, and patient outcomes subsequent to the implementation of increased levels of regulation.

Acknowledgments

This research was funded by the Department of Internal Medicine at the University of Nebraska Medical Center, Omaha, and by the Department of Internal Medicine at Abington Memorial Hospital, Philadelphia, Pennsylvania.

Busy clinicians have come to rely on the office laboratory as an important tool in providing timely, efficient, and high-quality patient care. However, concerns have been raised about poor accuracy in physician office laboratories and financial incentives that encourage overuse of tests.^1-7 Recent studies have documented inaccurate office laboratory testing.^8,9 Previously, the Commission on Office Laboratory Accreditation concluded that approximately 5% of office laboratories have serious deficiencies involving quality control, instrument maintenance, specimen management, and proficiency testing.¹⁰ Similar concerns led to the passage of the Clinical Laboratory Improvement Act of 1988 (CLIA-88), which was implemented in the fall of 1994.¹¹ Before CLIA-88, physician office laboratory quality regulations were decided at the state level.¹² Both state and federal regulations require adherence to specific measures (eg, proficiency testing, quality control, and quality assurance) to operate an office laboratory.

The critics of quality regulations assert that the measures might actually decrease the quality of care. They note that the regulations impose a fixed cost on the physician’s practice that must be spent regardless of how busy the laboratory is. The additional costs of compliance could discourage physicians from offering tests that would otherwise be done.^13,14 This reduction in test availability might occur in both high- and low-quality laboratories. Therefore, regulations aimed at improving quality might have the unintended effect of reducing the availability and use of clinically beneficial laboratory tests, thereby decreasing the overall potential benefit of the regulations.

We previously surveyed primary care physicians about their clinical approach to patients with a possible uncomplicated urinary tract infection (UTI).¹⁵ That 1994-1995 survey included primary care physicians in 4 states and contained detailed information on their work settings and clinical behavior concerning cases of UTI. In this paper we use those survey results to examine the potential effects of office laboratory quality regulations and test availability on testing for UTIs. This is possible because one of the states surveyed, Pennsylvania, has had statewide physician office laboratory quality regulations similar to CLIA-88 in place since the mid-1970s.^12,16 All office laboratories in Pennsylvania were required to register with the state, have a written procedure manual, perform quality and proficiency testing, and comply with state regulations, regardless of the level of testing.¹⁶ Office laboratories in the other 3 states were not regulated until the implementation of CLIA-88 in late 1994. Thus, the survey includes 1 regulated state and 3 states that were just beginning to be regulated. This should provide a conservative estimate of the differences between a regulated and a nonregulated situation, since some of the physicians in the previously unregulated states may already have adjusted to CLIA-88 when our survey was done. The adjustment to CLIA-88 did not occur instantaneously; laboratories have continued to move toward a higher percentage of waived and provider-performed microscopy laboratories (from 57.8% of all laboratories in 1995 to 75% in July 2000) since CLIA-88 was implemented.¹⁷ We sought to determine if office laboratory testing capabilities or availability differs by state and if self-reported use of the tests in diagnosing an uncomplicated UTI is related to the availability of the tests.

Methods

We examined the results of an 88-item survey concerning each physician’s clinical approach to patients with a possible UTI. We mailed the survey in 1994 and 1995 to practicing primary care physicians in 4 specialties that commonly treat adults with uncomplicated UTIs: general internal medicine, family practice, obstetrics and gynecology, and emergency medicine. The emergency medicine physicians were excluded from this analysis, since most of these physicians are hospital based and do not have an office laboratory in the same sense as the other specialties. To obtain a geographically diverse sample, we surveyed physicians from 4 states: Alabama, Nebraska, Minnesota, and Pennsylvania. The names and addresses of potential respondents were obtained from the physician masterfile of the American Medical Association (AMA). Since the AMA masterfile has limited data on physician characteristics (eg, the physician’s specialty), all data in our analysis were based on self-reported survey results. We surveyed the entire population of eligible physicians in each state except Pennsylvania; a random sample was chosen from Pennsylvania because of the large number of practicing physicians in that state.

The survey asked detailed questions about each physician’s clinical approach to a 30-year-old woman with dysuria, a presentation suggestive but not diagnostic of a UTI.^18,19 The main outcomes included whether specific tests (urine dipstick, microscopic urinalysis [UA], wet prep, and urine culture) were available in the office and whether these tests were used when diagnosing a UTI in the given patient. In both parts of the analysis we controlled for possible confounding variables. These included items reflecting the physician’s belief in the usefulness of clinical and laboratory information in diagnosing UTIs and physician and practice characteristics. The variables used in the analyses are shown in Table 1.

In the first part of the analysis we determined whether practicing in a regulated state (Pennsylvania) is associated with changes in the likelihood of having tests available in the office. The 4 outcome variables in this part of the analysis included the presence or absence of the dipstick, microscopic UA, wet prep, and urine culture. Thus, test availability was analyzed using binary dependent variables (yes=the physician reported the test in the office; no=otherwise). We did multivariate logistic regressions because of the binary nature of the dependent variables. Variables explaining the presence or absence of the test in the office included the key variable of interest: the physician’s state of residence (either in Pennsylvania or 1 of the previously unregulated states) and the group of variables reflecting the clinical beliefs concerning history, physical examination, and test usefulness in diagnosing UTI in our hypothetical patient, as well as physician, practice, and community characteristics. The explanatory variables were included in the regression models to control for any factors that might confound the effects of being from Pennsylvania. We hypothesized that tests would be found less frequently in Pennsylvania when controlling for other factors.

In the second part of the analysis, we examined whether the availability of tests in the office is related to their use in diagnosing UTIs in the hypothetical patient. The outcome variables in the second part were the self-reported frequency of ordering microscopic UA, urine culture, and the urine dipstick test (the leukocyte esterase and/or the nitrite test). Test use was analyzed as a binary variable (yes=the physician sometimes or usually performed the test; no=the physician rarely did the test). We did not have information on the physician’s use of the wet prep test, so we could not analyze the relationship between availablity and use for the wet prep. Because we analyzed the variable representing test use as a binary variable, we also used logistic regression for the analysis in the second part. In each regression, the variables explaining the frequency of using the test included 3 outcome measures from the first part of the analysis (whether the dipstick, micro UA, or culture was available in the office), and the same control variables reflecting physician beliefs and the personal and practice characteristics used in the first part of the analysis. We hypothesized that test availability would be related to its use in diagnosing UTIs after controlling for other relevant factors.

We used the Stata statistical software program²⁰ for the analysis.

Results

A total of 8942 surveys were sent out. There were 2172 usable surveys returned. After excluding the responses from the 274 emergency medicine physicians, we analyzed the remaining 1898 responses. We were able to compare respondents and nonrespondents on 3 demographic characteristics: sex, board-certification status, and length of time since graduating from medical school. The survey responders were more likely to be board certified but otherwise were similar to nonrespondents Table 2. Comparison of response patterns in Pennsylvania and the other 3 states using logistic regression indicates that Pennsylvania respondents were less likely to be men than respondents from other states. The magnitude of these differences, however, appears small.

Analysis of Test Availability

The reported prevalence of the various diagnostic tests in office laboratories is shown in Table 3. The dipstick is the most common test; more than 90% of respondents reported having it in their offices. The culture was the least available test, and the prevalence of both the microscopic UA and wet prep were intermediate between the culture and the dipstick. Simple unadjusted comparisons indicate that for each test physicians’ offices in Pennsylvania were less likely to report that they have the test available than were physicians in the unregulated states (P <.0001).

Table 4 shows the determinants of test availability from the multivariate logistic regressions. After controlling for possibly confounding factors, physicians from Pennsylvania were much less likely to have each of the tests in the office. The odds ratios (ORs) range from 0.20 (for the microscopic UA) to 0.35 (for the dipstick). Each of these results is statistically significant.

A number of control variables were significantly related to test availability.* Important findings include the effects of the physician’s specialty, clinical beliefs, and the estimated number of patients with dysuria seen per week. General internal medicine physicians were less likely than family practitioners to have each of the tests in the office (OR = 0.14, 0.60, 0.35, 0.57 for the dipstick, micro UA, wet prep, and culture; all P values <.05), while obstetrician-gynecologists were significantly less likely than family practitioners to have a dipstick, micro UA, and culture (OR = 0.14, 0.24, 0.44; all P values <.05) but more likely to have a wet prep available (OR=5.46; P=.0001). Increased belief in the importance of the leukocyte eserase test for diagnosing UTIs was associated with an increase in dipstick availability (OR=3.40; P=.0001), and increased belief in the importance of the microscopic white cell and red cell readings for diagnosing UTIs was associated with an increase in micro UA availability (OR = 1.95, 1.83; P = .01, .001, respectively). Seeing an additional patient per week with dysuria was associated with an increased availability for the dipstick (OR=1.12; P=.04), micro UA (OR=1.06; P=.01), and wet prep (OR=1.06; P=.02).

The overall explanatory power of these models was fairly good. The C-statistic, representing the area under the receiver operating characteristic curve, ranged from 0.75 for the urine culture to 0.93 for the dipstick (a C-statistic of 0.5 indicates that the model is no better than random chance at predicting the outcome, while a C-statistic of 1 indicates perfect discriminating ability).

Test Availability and the Diagnostic Approach

The relationship between test availability and use demonstrates that the availability of some tests is associated with an increase in their use, while sometimes the availability of tests is associated with an increase or decrease in the use of other tests Table 5. That is, tests will sometimes substitute for or complement other tests when diagnosing UTIs. Physicians with a microscopic UA in the office were more likely to report ordering a microscopic UA. The presence of the urine culture increased microscopic UA use, but the dipstick, when available, appeared to substitute for the microscopic UA.

The reported frequency of ordering urine cultures was increased by the availability of a culture but was decreased when respondents reported having a microscopic UA or dipstick available.

The dipstick was the only test for which use was not significantly related to the presence of any of the diagnostic tests; the availability of the dipstick appears to increase its use, but this relationship was not significant.

Even though test availability is often related to use, the physician may not be the person actually doing the tests. Of the 1492 physicians who report sometimes or usually ordering microscopic UAs, 363 do the procedure themselves, and 803 use ancillary personnel in their office. The remainder (326) have the procedure done outside the office. In contrast, only 25 of the physicians who report sometimes or usually ordering a urine culture do the test themselves. Three hundred forty-two use ancillary help in the office, and 243 have the culture done at an outside laboratory.

Several physician and practice characteristics were significantly related to the frequency of ordering each of the diagnostic tests. Being an obstetrician-gynecologist relative to family practitioner decreased microscopic UA use (OR=0.41; P=.0001), while a greater belief in the value of the leukocyte esterase test decreased microscopic UA use (OR=0.70; P=.01), and greater belief in the microscopic white cell reading increased use of the microscopic UA (OR=3.12; P=.0001). Increased use of urine cultures was associated with being in a city with a population greater than 100,000 relative to a town of less than 10,000 (OR=1.54; P=.02) and being a government employee relative to being in private practice (OR=9.31; P=.0001), while culture use was decreased in practice sizes of more than 25 physicians relative to being in solo practice (OR=0.39; P=.004). The dipstick was used more commonly when physicians had a greater belief in the value of the leukocyte esterase (OR=5.15; P=.0001) and nitrite (OR=2.68; P=.0001) results. Interestingly, the physician’s specialty was generally not significantly related to test use (apart from the difference between obstetrician-gynecologists and family practitioners in micro UA use), in contrast to the consistent specialty differences found for test availability.

The overall power of each of these models to explain the frequency of test use was moderately good. The C-statistics ranged from 0.69 for ordering a urine culture to 0.82 for ordering the dipstick.

Discussion

This study has 2 main findings. First, for each of the office laboratory tests examined, we found significant differences in test availability between unregulated states and Pennsylvania, a state with a long-standing physician office laboratory regulatory system. The overall pattern is one of diminished test availability in Pennsylvania, after controlling for other explanatory influences. This finding was present for every test we examined, regardless of the cost of performing the test or the level at which it was regulated. This supports the hypothesis that tests are available less often in a regulated state.

The second main finding is that the physician’s diagnostic approach to UTIs was related to the in-office availability of tests. This finding supports our second hypothesis. However, the relationship between test and availability and use was more complex than suspected. Not only was the self-reported use of some tests (microscopic UA and culture) related to their availability, sometimes the availability of a test was associated with a change in the self-reported frequency of using other tests. Thus, some tests appear to substitute for others (availability of the dipstick reduces use of microscopic UAs and cultures, and availability of the microscopic UA decreases culture ordering), while the availability of the culture was associated with increased use of the microscopic UA. We also found significant relationships between the physician’s belief in the usefulness of test results in diagnosing UTI with both the availability and subsequent use of the diagnostic tests.

The multivariate analyses indicated that physician and practice characteristics were related to the availability and use of diagnostic tests. This finding is consistent with previous studies reporting numerous factors influencing the use of laboratory tests.^21-23 To our knowledge, the association between physician belief in the value of the test in diagnosing a condition and test availability and use has not been documented previously. Thus, the influence of quality regulations on test prevalence and use will be modulated by the configuration of these other factors.

This study differs from previous studies on laboratory use in that we have been able to control for many relevant explanatory variables, including the physician’s belief in the diagnostic importance of elements from the patient’s history, physical examination, and test results. Many of these items add significant predictive power in a “logical” direction. For example, the availability of many tests was related to the physician’s belief in the value of the results provided by that test, and these beliefs were related to the physician’s diagnostic approach. Although it is not possible to tell from the survey if the physician’s belief in the usefulness of the test is causally related to the availability of a test, the results indicate the need to control for physician-specific opinions and beliefs when examining laboratory test use.

It is not possible to determine the net effect of quality regulations on patient welfare from this study. In theory, a reduction in test availability and subsequent use of a less accurate diagnostic approach is offset by higher quality and accuracy in those offices still offering tests.²⁴ We did not measure the quality or accuracy of the physician’s laboratory testing. To the extent that poor-quality laboratories are closed, regulations should improve overall welfare. Alternatively, if the reduction in test availability occurs in both good- and bad-quality laboratories, then the net effects on patient outcomes may be negative. A recent cost-effectiveness study of tests used to diagnose UTIs²⁵ indicated that the microscopic UA was reasonably cost-effective ($2964 per quality-adjusted life month), but the low sensitivity of the dipstick resulted in a poor cost-effectiveness ratio ($48,460 per quality-adjusted life month). Thus, to the extent that the highly prevalent dipstick is substituting for more cost-effective tests, as our results suggest, regulations might lead to less cost-effective care.

Our analysis suggests that changing the availability of tests may change physicians’ diagnostic approaches in ways that are difficult to predict a priori. For example, reducing the availability of the microscopic UA might lead to greater use of the more expensive urine culture. When many tests are reduced in availability, it is difficult to anticipate how the care of patients will change, since tests will substitute for or complement the use of other tests in ways that are difficult to predict.

Limitations

This study has several limitations. First, it is based on survey data that may not reflect actual behavior. However, the results are plausible, internally consistent, and consistent with previous research findings documenting substantial variation in practice patterns in managing UTIs.²⁶ Our focus on how physicians treat an uncomplicated basic UTI limits the possibility of eliciting responses based on unmeasured patient characteristics. Second, the overall response rate was low, which might raise concerns that the respondents represent an atypical or biased group of physicians. A comparison of respondents and nonrespondents along the 3 characteristics we had access to did not reveal any striking differences. And, when compared with nationwide physician work force statistics collected by the AMA in 1994, the physicians in this study had similar hours per week spent in patient care (46.2 in our survey vs 48.2 in the AMA survey) and estimated level of capitation (19.3% in our survey vs 16.7% in the AMA survey).²⁷ The estimated volume of patients with UTI was also similar to previous surveys of primary care physicians (approximately 6 per week).²⁶ Thus, the respondents in this survey do not seem to represent an atypical or unusual group of physicians. Other limitations include the fact that physicians responding to the survey might not be responsible for deciding whether to acquire or maintain tests in the office. Likewise, the survey does not contain information on other factors in the physician’s local market that might influence the supply or demand for office tests. These effects, however, would have to be quite large and disproportionately affect Pennsylvania respondents to confound our findings.

Finally, since the analysis is based on cross-sectional data, the results do not give any indication of how rapidly in-office testing declines after the implementation of quality regulations. However, as mentioned before, statistics indicate that the mix of tests in physicians’ offices has continued to move towards simpler tests since CLIA-88 was implemented. Our study provides a snapshot of the circumstances as CLIA-88 was first implemented; it would be worthwhile to assess changes in test prevalence and use in our survey population over the last several years. It may be the case that other changes underway in health care delivery (eg, improving technology, vertical and horizontal integration of physician groups, and growth of managed care) may hasten or reverse the changes in office laboratory availability implied in this study.

Conclusions

The availability of common office tests used in the diagnosis of UTI appears to be related to many factors, including the presence of office laboratory regulations. Lower availability of tests, in turn, was associated with the diagnostic approach when treating patients with a possible UTI. The net effects on patient welfare are difficult to predict, but our findings raise a serious concern about the possibility of a detrimental overall effect on patient welfare. Determining the full effect of quality regulations will require careful study to measure the changes in treatment patterns, treatment quality, and patient outcomes subsequent to the implementation of increased levels of regulation.

Acknowledgments

This research was funded by the Department of Internal Medicine at the University of Nebraska Medical Center, Omaha, and by the Department of Internal Medicine at Abington Memorial Hospital, Philadelphia, Pennsylvania.