Use of Microalbuminuria Testing in Persons with Type 2 Diabetes: Are the Right Patients Being Tested?

Nephropathy is one of the most common long-term side effects of diabetes mellitus and accounts for the largest percentage of patients requiring chronic renal dialysis in the United States and Europe.^1,2 The high prevalence of type 2 diabetes among adults in the United States and the high rate of nephropathy in these individuals pose a great economic burden to the health care system.

Several studies have noted that angiotensin-converting enzyme inhibitors (ACEIs) can delay the progression of renal impairment in patients with type 2 diabetes.^3-7 Patients with diabetic nephropathy generally progress from a stage of normal renal function to microalbuminuria, gross proteinuria, and then renal dysfunction.¹ ACEIs appear to delay or prevent the progression from microalbuminuria to proteinuria. Although there are no controlled trials that show microalbuminuria screening as effective at reducing proteinuria, expert panels of the American Diabetes Association⁸ and National Kidney Foundation⁹ have recommended that patients with type 2 diabetes receive annual screening for microalbuminuria, and if it is detected on 2 of 3 occasions, these patients should be placed on an ACEI or an angiotensin receptor blocker (ARB) for renal protection.

Initial evaluation of data from primary care practices, however, reveals that screening for microalbuminuria is not optimal.^10,11 One reason microalbuminuria screening may happen less often than expected could be that many patients with diabetes mellitus are already being treated with an ACEI or ARB for hypertension, congestive heart failure, or other reasons. Some physicians also might employ an ACEI or ARB prophylactically, starting treatment before recognizing microalbuminuria. Given that these patients are already being treated with an ACEI or ARB, clinicians may not recognize any usefulness in performing a microalbuminuria test.

The purpose of our study was to examine what patient factors are associated with screening for microalbuminuria in patients with type 2 diabetes mellitus. Specifically, we examined how often patients who were not screened were already being treated with an ACEI or ARB. Also, we hoped to characterize the populations being screened more fully to determine if certain patient and disease characteristics were associated with the likelihood of a screening test being performed. A better awareness of these characteristics will help in targeting specific patient groups and changing physician behavior.

Methods

Sample

Our sample was drawn from the primary care practice in the department of family medicine at the Medical University of South Carolina (MUSC) in 1998 and 1999. The department provided care for approximately 18,000 patients who made 42,000 and 48,000 patient visits in 1998 and 1999, respectively, at 2 clinical sites. These 2 sites serve a diverse population of patients in downtown Charleston and a nearby suburban area, which in 1998 had a payer mix distribution that was 26% Medicaid, 27% Medicare, 37% commercially insured, and 10% self-pay.

We identified patients with diabetes at the 2 clinical sites from a search of the problem list in an electronic medical record database that has been used in the department of family medicine since 1992 Table 1. All patients aged between 18 years and 65 years in 2000 and who had an appointment scheduled in 1998 or 1999 were included. The charts that were initially selected for review had diabetes mellitus listed as a problem; after the chart review, we excluded 18 patients from the study because they were using insulin or had not been seen in the practices since 1995, even though they had scheduled an appointment in 1998 or 1999. This left a final sample size of 278.

Data Collection and Variables

Two medical students performed the chart reviews and recorded the following variables when available: age, weight, sex, serum creatinine level, hemoglobin A_1C (Hb A_1C) level, proteinuria on urinalysis testing, blood pressure, total serum cholesterol, and whether a microalbuminuria test was recommended and, if performed, the results. Race was not included because the patient charts do not consistently note the patient’s race. Also, because care is often shared between attending and resident physicians, we did not include the physician training level as a variable in our analysis.

To determine whether patients were on ACEI or ARB therapy, we searched the electronic medical record database for all medications in the previous 5 years. The medical record used during this period required all prescriptions to be entered before a printed version could be generated, so we could determine if a drug had been used in the past. Although this system overlooked prescriptions that might be called in to a pharmacy and not documented in the record, it captured every prescription written by a physician in the practice. When an ACEI or ARB was used, we examined whether the medication had been started before screening was indicated or after a microalbuminuria test was performed.

We searched the laboratory section of the electronic medical record and also the hospital patient database to determine if the hospital laboratory had performed the test. Searching the hospital database would indicate if the test was performed by any other clinician (eg, an endocrinologist) or in another setting (eg, inpatient) in the university medical center. Whether a microalbuminuria test was recommended was recorded, with the returned value (if available) and the date the test was recommended. We considered values greater than 20 mg per L positive for microalbuminuria. Protein-uria tests were considered positive if they returned a 1+ protein or greater result. We also recorded whether the subject was on an ACEI or ARB therapy, and if so at what date it had been prescribed.

To minimize inter-rater variability, the 2 medical students each reviewed a pilot sample of the same 20 charts. Data were compared and differences between the auditors were reviewed to standardize definitions of data elements. After standardization, sets of 10 different charts were selected, and the process was repeated until the data from 40 consecutive charts were recorded identically by both students.

Analysis

When comparing mean values, we performed a Student t test to determine statistical significance. A chi-square test was done to determine statistical significance when comparing proportions. A P value of <.05 was determined to be statistically significant.

Results

Of the 278 eligible patients, 44 (16%) had a urinalysis with 1+ or greater protein result at baseline; 18 (41%) of these were already taking an ACEI or ARB drug. In patients without previous evidence of proteinuria, 51 (18%) patients were using ACEI or ARB therapy. This left 183 patients (66%) who had no evidence of renal disease and who were not using ACEI or ARB therapy and therefore were the prime candidates for microalbuminuria screening Figure 1.

When we examined the demographics and clinical variables of these 3 groups, we found that patients with proteinuria or who were already using drug treatment were older and had higher systolic and diastolic blood pressures than those who were not. Unexpectedly, we also found that patients with existing proteinuria had lower Hb A_1C levels than patients in the other 2 categories.

Of these prime candidates for screening, only 31 (17%) received at least 1 microalbuminuria test between 1995 and 1999. The rate of screening in this group was no different from those who were taking an ACEI or ARB drug (16%, P=.83) or already had gross proteinuria (18%, P=.84).

When we examined the patients who were most likely to benefit from screening and looked at demographic or clinical factors that might influence whether a screening test was performed, we found that patients who received microalbuminuria testing were very similar to those who did not. The only difference we found was that patients who received screening had lower systolic blood pressures than those who were not screened. Weight, age, Hb A_1C levels, and cholesterol levels were not predictors of being screened for microalbuminuria Table 2.

Because of the low rates of microalbuminuria screening for patients who were eligible and the relatively frequent use of screening in patients who already had evidence of gross proteinuria, we were interested in what clinicians did when a microalbuminuria test result was positive. In the group without evidence of proteinuria and not using ACEI or ARB therapy, 10 of the 31 patients who received screening for microalbuminuria tested positive. However, only 4 (40%) were placed on ACE inhibitor or ARB therapy.

Discussion

Our data suggest that several problems exist in the use and interpretation of microalbuminuria testing in the primary care setting. First, microalbuminuria testing is being performed on only 1 of 5 adult patients with type 2 diabetes. Second, in this practice, testing is not targeted to the patients who are most likely to benefit from the results. Rather, the tests seemed to be used indiscriminately. Finally, even when patients are screened and found to have microalbuminuria, only a small percentage were started on appropriate therapy. At least in this patient population, it appears that ACEI or ARB therapy is reserved for patients with higher blood pressures rather than used for renal protection.

The observation that patients with existing proteinuria or who were on ACEI or ARB therapy were screened just as often as those who were prime candidates for screening contradicts our initial hypothesis. We had assumed that clinicians would not screen patients who were on ACEI or ARB therapy, reducing the overall screening rate. Apparently, this is not the case. At least in this practice, a low screening rate is not due to selective screening.

The lack of optimal use of microalbuminuria testing and the failure to respond appropriately to positive test results suggests that current recommendations have not been embraced by physicians. Also, the complexity of carrying out these recommendations may make it difficult to integrate this screening into routine practice. If the current evidence on ACEI and ARB therapy for the prevention of renal dysfunction is to be translated into practice, either greater emphasis needs to be placed on microalbuminuria screening or more efficient ways to provide renal protection for patients with diabetes should be considered. Other studies have found that between 17% and 30% of patients with type 2 diabetes have microalbuminuria.^1,12,13 Although primary care physicians report that they provide microalbuminuria screening to a large percentage of their patients with diabetes, in fact only a small percentage of those who should be screened actually are screened.¹⁰ Suboptimal screening rates for important conditions seen in primary care are not unique for microalbuminuria. Other studies have documented comparable low screening rates for a wide variety of cancers.¹⁴ Since physicians do not screen reliably for potentially fatal diseases with screening modalities that have been available for decades, it is unlikely that their behavior is likely to improve when asked to screen for microalbuminuria.

Also, recent evidence that ACEI therapy may improve endothelial function in patients with type 2 diabetes suggests that even patients without microalbuminuria may benefit from routine ACEI therapy.¹⁵ Other studies suggest that routine use of ACEIs in middle-aged patients with type 2 diabetes may provide substantial benefits at only modest costs compared with a screening strategy.¹⁶ These data suggest that a more effective strategy would be to advise that all patients with type 2 diabetes start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while assuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. However, using this strategy, patients who may not have proteinuria will have to take the medication for a prolonged period, pay for it, and run the risks for any complications associated with using the drug.

Limitations

Our study has several limitations. Only 1 practice was examined, and it was part of a residency training practice. This means that less-experienced clinicians were providing care that could reduce the overall rate of screening. However, the rate of screening observed in this study was very similar to rates found in the practices of clinicians with more experience,^11,12 suggesting that the lack of experience of resident physicians may be balanced by the oversight provided by faculty preceptors.

Another limitation is that it was not possible to account for microalbuminuria screening completed outside the MUSC medical center. Patients who split their care among several providers could have had testing performed in other health care facilities. However, since more than 95% of the referrals from the MUSC Family Medicine Center stay within the university health care system, it is doubtful that many patients would have received testing outside the search capabilities of the hospital laboratory database.

Finally, the study was limited in its power to detect small differences between the groups. We originally conceived our project as an exploratory study to determine how many patients were already taking ACEIs and the potential effect of this on overall screening rates for microalbuminuria. Without any reference for the percentage of patients who were taking ACEIs, we could not perform an ad hoc power analysis. However, a post hoc analysis shows that for a sample in which the groups are matched in a 1-to-3 ratio (approximating the proportion of the 51 patients in our sample taking ACEIs and the 183 not taking these drugs) and given the study sample size, our study had a power of 80% to detect a difference in screening rates between 20% in the baseline group and 5% in the ACE or ARB groups. The actual difference seen in our study was much smaller, which increases the possibility of a type II error.

Conclusions

Because physician use of microalbuminuria screening does not follow established guidelines, consideration should be given to other strategies to prevent nephropathy in persons with type 2 diabetes. One proposed strategy would advise all patients with type 2 diabetes to start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while ensuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. It is unknown, however, whether patients would accept universal treatment rather than periodic screening. This is an important question that should be addressed before any population-based strategies are adopted.

Nephropathy is one of the most common long-term side effects of diabetes mellitus and accounts for the largest percentage of patients requiring chronic renal dialysis in the United States and Europe.^1,2 The high prevalence of type 2 diabetes among adults in the United States and the high rate of nephropathy in these individuals pose a great economic burden to the health care system.

Several studies have noted that angiotensin-converting enzyme inhibitors (ACEIs) can delay the progression of renal impairment in patients with type 2 diabetes.^3-7 Patients with diabetic nephropathy generally progress from a stage of normal renal function to microalbuminuria, gross proteinuria, and then renal dysfunction.¹ ACEIs appear to delay or prevent the progression from microalbuminuria to proteinuria. Although there are no controlled trials that show microalbuminuria screening as effective at reducing proteinuria, expert panels of the American Diabetes Association⁸ and National Kidney Foundation⁹ have recommended that patients with type 2 diabetes receive annual screening for microalbuminuria, and if it is detected on 2 of 3 occasions, these patients should be placed on an ACEI or an angiotensin receptor blocker (ARB) for renal protection.

Initial evaluation of data from primary care practices, however, reveals that screening for microalbuminuria is not optimal.^10,11 One reason microalbuminuria screening may happen less often than expected could be that many patients with diabetes mellitus are already being treated with an ACEI or ARB for hypertension, congestive heart failure, or other reasons. Some physicians also might employ an ACEI or ARB prophylactically, starting treatment before recognizing microalbuminuria. Given that these patients are already being treated with an ACEI or ARB, clinicians may not recognize any usefulness in performing a microalbuminuria test.

The purpose of our study was to examine what patient factors are associated with screening for microalbuminuria in patients with type 2 diabetes mellitus. Specifically, we examined how often patients who were not screened were already being treated with an ACEI or ARB. Also, we hoped to characterize the populations being screened more fully to determine if certain patient and disease characteristics were associated with the likelihood of a screening test being performed. A better awareness of these characteristics will help in targeting specific patient groups and changing physician behavior.

Methods

Sample

Our sample was drawn from the primary care practice in the department of family medicine at the Medical University of South Carolina (MUSC) in 1998 and 1999. The department provided care for approximately 18,000 patients who made 42,000 and 48,000 patient visits in 1998 and 1999, respectively, at 2 clinical sites. These 2 sites serve a diverse population of patients in downtown Charleston and a nearby suburban area, which in 1998 had a payer mix distribution that was 26% Medicaid, 27% Medicare, 37% commercially insured, and 10% self-pay.

We identified patients with diabetes at the 2 clinical sites from a search of the problem list in an electronic medical record database that has been used in the department of family medicine since 1992 Table 1. All patients aged between 18 years and 65 years in 2000 and who had an appointment scheduled in 1998 or 1999 were included. The charts that were initially selected for review had diabetes mellitus listed as a problem; after the chart review, we excluded 18 patients from the study because they were using insulin or had not been seen in the practices since 1995, even though they had scheduled an appointment in 1998 or 1999. This left a final sample size of 278.

Data Collection and Variables

Two medical students performed the chart reviews and recorded the following variables when available: age, weight, sex, serum creatinine level, hemoglobin A_1C (Hb A_1C) level, proteinuria on urinalysis testing, blood pressure, total serum cholesterol, and whether a microalbuminuria test was recommended and, if performed, the results. Race was not included because the patient charts do not consistently note the patient’s race. Also, because care is often shared between attending and resident physicians, we did not include the physician training level as a variable in our analysis.

To determine whether patients were on ACEI or ARB therapy, we searched the electronic medical record database for all medications in the previous 5 years. The medical record used during this period required all prescriptions to be entered before a printed version could be generated, so we could determine if a drug had been used in the past. Although this system overlooked prescriptions that might be called in to a pharmacy and not documented in the record, it captured every prescription written by a physician in the practice. When an ACEI or ARB was used, we examined whether the medication had been started before screening was indicated or after a microalbuminuria test was performed.

We searched the laboratory section of the electronic medical record and also the hospital patient database to determine if the hospital laboratory had performed the test. Searching the hospital database would indicate if the test was performed by any other clinician (eg, an endocrinologist) or in another setting (eg, inpatient) in the university medical center. Whether a microalbuminuria test was recommended was recorded, with the returned value (if available) and the date the test was recommended. We considered values greater than 20 mg per L positive for microalbuminuria. Protein-uria tests were considered positive if they returned a 1+ protein or greater result. We also recorded whether the subject was on an ACEI or ARB therapy, and if so at what date it had been prescribed.

To minimize inter-rater variability, the 2 medical students each reviewed a pilot sample of the same 20 charts. Data were compared and differences between the auditors were reviewed to standardize definitions of data elements. After standardization, sets of 10 different charts were selected, and the process was repeated until the data from 40 consecutive charts were recorded identically by both students.

Analysis

When comparing mean values, we performed a Student t test to determine statistical significance. A chi-square test was done to determine statistical significance when comparing proportions. A P value of <.05 was determined to be statistically significant.

Results

Of the 278 eligible patients, 44 (16%) had a urinalysis with 1+ or greater protein result at baseline; 18 (41%) of these were already taking an ACEI or ARB drug. In patients without previous evidence of proteinuria, 51 (18%) patients were using ACEI or ARB therapy. This left 183 patients (66%) who had no evidence of renal disease and who were not using ACEI or ARB therapy and therefore were the prime candidates for microalbuminuria screening Figure 1.

When we examined the demographics and clinical variables of these 3 groups, we found that patients with proteinuria or who were already using drug treatment were older and had higher systolic and diastolic blood pressures than those who were not. Unexpectedly, we also found that patients with existing proteinuria had lower Hb A_1C levels than patients in the other 2 categories.

Of these prime candidates for screening, only 31 (17%) received at least 1 microalbuminuria test between 1995 and 1999. The rate of screening in this group was no different from those who were taking an ACEI or ARB drug (16%, P=.83) or already had gross proteinuria (18%, P=.84).

When we examined the patients who were most likely to benefit from screening and looked at demographic or clinical factors that might influence whether a screening test was performed, we found that patients who received microalbuminuria testing were very similar to those who did not. The only difference we found was that patients who received screening had lower systolic blood pressures than those who were not screened. Weight, age, Hb A_1C levels, and cholesterol levels were not predictors of being screened for microalbuminuria Table 2.

Because of the low rates of microalbuminuria screening for patients who were eligible and the relatively frequent use of screening in patients who already had evidence of gross proteinuria, we were interested in what clinicians did when a microalbuminuria test result was positive. In the group without evidence of proteinuria and not using ACEI or ARB therapy, 10 of the 31 patients who received screening for microalbuminuria tested positive. However, only 4 (40%) were placed on ACE inhibitor or ARB therapy.

Discussion

Our data suggest that several problems exist in the use and interpretation of microalbuminuria testing in the primary care setting. First, microalbuminuria testing is being performed on only 1 of 5 adult patients with type 2 diabetes. Second, in this practice, testing is not targeted to the patients who are most likely to benefit from the results. Rather, the tests seemed to be used indiscriminately. Finally, even when patients are screened and found to have microalbuminuria, only a small percentage were started on appropriate therapy. At least in this patient population, it appears that ACEI or ARB therapy is reserved for patients with higher blood pressures rather than used for renal protection.

The observation that patients with existing proteinuria or who were on ACEI or ARB therapy were screened just as often as those who were prime candidates for screening contradicts our initial hypothesis. We had assumed that clinicians would not screen patients who were on ACEI or ARB therapy, reducing the overall screening rate. Apparently, this is not the case. At least in this practice, a low screening rate is not due to selective screening.

The lack of optimal use of microalbuminuria testing and the failure to respond appropriately to positive test results suggests that current recommendations have not been embraced by physicians. Also, the complexity of carrying out these recommendations may make it difficult to integrate this screening into routine practice. If the current evidence on ACEI and ARB therapy for the prevention of renal dysfunction is to be translated into practice, either greater emphasis needs to be placed on microalbuminuria screening or more efficient ways to provide renal protection for patients with diabetes should be considered. Other studies have found that between 17% and 30% of patients with type 2 diabetes have microalbuminuria.^1,12,13 Although primary care physicians report that they provide microalbuminuria screening to a large percentage of their patients with diabetes, in fact only a small percentage of those who should be screened actually are screened.¹⁰ Suboptimal screening rates for important conditions seen in primary care are not unique for microalbuminuria. Other studies have documented comparable low screening rates for a wide variety of cancers.¹⁴ Since physicians do not screen reliably for potentially fatal diseases with screening modalities that have been available for decades, it is unlikely that their behavior is likely to improve when asked to screen for microalbuminuria.

Also, recent evidence that ACEI therapy may improve endothelial function in patients with type 2 diabetes suggests that even patients without microalbuminuria may benefit from routine ACEI therapy.¹⁵ Other studies suggest that routine use of ACEIs in middle-aged patients with type 2 diabetes may provide substantial benefits at only modest costs compared with a screening strategy.¹⁶ These data suggest that a more effective strategy would be to advise that all patients with type 2 diabetes start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while assuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. However, using this strategy, patients who may not have proteinuria will have to take the medication for a prolonged period, pay for it, and run the risks for any complications associated with using the drug.

Limitations

Our study has several limitations. Only 1 practice was examined, and it was part of a residency training practice. This means that less-experienced clinicians were providing care that could reduce the overall rate of screening. However, the rate of screening observed in this study was very similar to rates found in the practices of clinicians with more experience,^11,12 suggesting that the lack of experience of resident physicians may be balanced by the oversight provided by faculty preceptors.

Another limitation is that it was not possible to account for microalbuminuria screening completed outside the MUSC medical center. Patients who split their care among several providers could have had testing performed in other health care facilities. However, since more than 95% of the referrals from the MUSC Family Medicine Center stay within the university health care system, it is doubtful that many patients would have received testing outside the search capabilities of the hospital laboratory database.

Finally, the study was limited in its power to detect small differences between the groups. We originally conceived our project as an exploratory study to determine how many patients were already taking ACEIs and the potential effect of this on overall screening rates for microalbuminuria. Without any reference for the percentage of patients who were taking ACEIs, we could not perform an ad hoc power analysis. However, a post hoc analysis shows that for a sample in which the groups are matched in a 1-to-3 ratio (approximating the proportion of the 51 patients in our sample taking ACEIs and the 183 not taking these drugs) and given the study sample size, our study had a power of 80% to detect a difference in screening rates between 20% in the baseline group and 5% in the ACE or ARB groups. The actual difference seen in our study was much smaller, which increases the possibility of a type II error.

Conclusions

Because physician use of microalbuminuria screening does not follow established guidelines, consideration should be given to other strategies to prevent nephropathy in persons with type 2 diabetes. One proposed strategy would advise all patients with type 2 diabetes to start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while ensuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. It is unknown, however, whether patients would accept universal treatment rather than periodic screening. This is an important question that should be addressed before any population-based strategies are adopted.

Nephropathy is one of the most common long-term side effects of diabetes mellitus and accounts for the largest percentage of patients requiring chronic renal dialysis in the United States and Europe.^1,2 The high prevalence of type 2 diabetes among adults in the United States and the high rate of nephropathy in these individuals pose a great economic burden to the health care system.

Several studies have noted that angiotensin-converting enzyme inhibitors (ACEIs) can delay the progression of renal impairment in patients with type 2 diabetes.^3-7 Patients with diabetic nephropathy generally progress from a stage of normal renal function to microalbuminuria, gross proteinuria, and then renal dysfunction.¹ ACEIs appear to delay or prevent the progression from microalbuminuria to proteinuria. Although there are no controlled trials that show microalbuminuria screening as effective at reducing proteinuria, expert panels of the American Diabetes Association⁸ and National Kidney Foundation⁹ have recommended that patients with type 2 diabetes receive annual screening for microalbuminuria, and if it is detected on 2 of 3 occasions, these patients should be placed on an ACEI or an angiotensin receptor blocker (ARB) for renal protection.

Initial evaluation of data from primary care practices, however, reveals that screening for microalbuminuria is not optimal.^10,11 One reason microalbuminuria screening may happen less often than expected could be that many patients with diabetes mellitus are already being treated with an ACEI or ARB for hypertension, congestive heart failure, or other reasons. Some physicians also might employ an ACEI or ARB prophylactically, starting treatment before recognizing microalbuminuria. Given that these patients are already being treated with an ACEI or ARB, clinicians may not recognize any usefulness in performing a microalbuminuria test.

The purpose of our study was to examine what patient factors are associated with screening for microalbuminuria in patients with type 2 diabetes mellitus. Specifically, we examined how often patients who were not screened were already being treated with an ACEI or ARB. Also, we hoped to characterize the populations being screened more fully to determine if certain patient and disease characteristics were associated with the likelihood of a screening test being performed. A better awareness of these characteristics will help in targeting specific patient groups and changing physician behavior.

Methods

Sample

Our sample was drawn from the primary care practice in the department of family medicine at the Medical University of South Carolina (MUSC) in 1998 and 1999. The department provided care for approximately 18,000 patients who made 42,000 and 48,000 patient visits in 1998 and 1999, respectively, at 2 clinical sites. These 2 sites serve a diverse population of patients in downtown Charleston and a nearby suburban area, which in 1998 had a payer mix distribution that was 26% Medicaid, 27% Medicare, 37% commercially insured, and 10% self-pay.

We identified patients with diabetes at the 2 clinical sites from a search of the problem list in an electronic medical record database that has been used in the department of family medicine since 1992 Table 1. All patients aged between 18 years and 65 years in 2000 and who had an appointment scheduled in 1998 or 1999 were included. The charts that were initially selected for review had diabetes mellitus listed as a problem; after the chart review, we excluded 18 patients from the study because they were using insulin or had not been seen in the practices since 1995, even though they had scheduled an appointment in 1998 or 1999. This left a final sample size of 278.

Data Collection and Variables

Two medical students performed the chart reviews and recorded the following variables when available: age, weight, sex, serum creatinine level, hemoglobin A_1C (Hb A_1C) level, proteinuria on urinalysis testing, blood pressure, total serum cholesterol, and whether a microalbuminuria test was recommended and, if performed, the results. Race was not included because the patient charts do not consistently note the patient’s race. Also, because care is often shared between attending and resident physicians, we did not include the physician training level as a variable in our analysis.

To determine whether patients were on ACEI or ARB therapy, we searched the electronic medical record database for all medications in the previous 5 years. The medical record used during this period required all prescriptions to be entered before a printed version could be generated, so we could determine if a drug had been used in the past. Although this system overlooked prescriptions that might be called in to a pharmacy and not documented in the record, it captured every prescription written by a physician in the practice. When an ACEI or ARB was used, we examined whether the medication had been started before screening was indicated or after a microalbuminuria test was performed.

We searched the laboratory section of the electronic medical record and also the hospital patient database to determine if the hospital laboratory had performed the test. Searching the hospital database would indicate if the test was performed by any other clinician (eg, an endocrinologist) or in another setting (eg, inpatient) in the university medical center. Whether a microalbuminuria test was recommended was recorded, with the returned value (if available) and the date the test was recommended. We considered values greater than 20 mg per L positive for microalbuminuria. Protein-uria tests were considered positive if they returned a 1+ protein or greater result. We also recorded whether the subject was on an ACEI or ARB therapy, and if so at what date it had been prescribed.

To minimize inter-rater variability, the 2 medical students each reviewed a pilot sample of the same 20 charts. Data were compared and differences between the auditors were reviewed to standardize definitions of data elements. After standardization, sets of 10 different charts were selected, and the process was repeated until the data from 40 consecutive charts were recorded identically by both students.

Analysis

When comparing mean values, we performed a Student t test to determine statistical significance. A chi-square test was done to determine statistical significance when comparing proportions. A P value of <.05 was determined to be statistically significant.

Results

Of the 278 eligible patients, 44 (16%) had a urinalysis with 1+ or greater protein result at baseline; 18 (41%) of these were already taking an ACEI or ARB drug. In patients without previous evidence of proteinuria, 51 (18%) patients were using ACEI or ARB therapy. This left 183 patients (66%) who had no evidence of renal disease and who were not using ACEI or ARB therapy and therefore were the prime candidates for microalbuminuria screening Figure 1.

When we examined the demographics and clinical variables of these 3 groups, we found that patients with proteinuria or who were already using drug treatment were older and had higher systolic and diastolic blood pressures than those who were not. Unexpectedly, we also found that patients with existing proteinuria had lower Hb A_1C levels than patients in the other 2 categories.

Of these prime candidates for screening, only 31 (17%) received at least 1 microalbuminuria test between 1995 and 1999. The rate of screening in this group was no different from those who were taking an ACEI or ARB drug (16%, P=.83) or already had gross proteinuria (18%, P=.84).

When we examined the patients who were most likely to benefit from screening and looked at demographic or clinical factors that might influence whether a screening test was performed, we found that patients who received microalbuminuria testing were very similar to those who did not. The only difference we found was that patients who received screening had lower systolic blood pressures than those who were not screened. Weight, age, Hb A_1C levels, and cholesterol levels were not predictors of being screened for microalbuminuria Table 2.

Because of the low rates of microalbuminuria screening for patients who were eligible and the relatively frequent use of screening in patients who already had evidence of gross proteinuria, we were interested in what clinicians did when a microalbuminuria test result was positive. In the group without evidence of proteinuria and not using ACEI or ARB therapy, 10 of the 31 patients who received screening for microalbuminuria tested positive. However, only 4 (40%) were placed on ACE inhibitor or ARB therapy.

Discussion

Our data suggest that several problems exist in the use and interpretation of microalbuminuria testing in the primary care setting. First, microalbuminuria testing is being performed on only 1 of 5 adult patients with type 2 diabetes. Second, in this practice, testing is not targeted to the patients who are most likely to benefit from the results. Rather, the tests seemed to be used indiscriminately. Finally, even when patients are screened and found to have microalbuminuria, only a small percentage were started on appropriate therapy. At least in this patient population, it appears that ACEI or ARB therapy is reserved for patients with higher blood pressures rather than used for renal protection.

The observation that patients with existing proteinuria or who were on ACEI or ARB therapy were screened just as often as those who were prime candidates for screening contradicts our initial hypothesis. We had assumed that clinicians would not screen patients who were on ACEI or ARB therapy, reducing the overall screening rate. Apparently, this is not the case. At least in this practice, a low screening rate is not due to selective screening.

The lack of optimal use of microalbuminuria testing and the failure to respond appropriately to positive test results suggests that current recommendations have not been embraced by physicians. Also, the complexity of carrying out these recommendations may make it difficult to integrate this screening into routine practice. If the current evidence on ACEI and ARB therapy for the prevention of renal dysfunction is to be translated into practice, either greater emphasis needs to be placed on microalbuminuria screening or more efficient ways to provide renal protection for patients with diabetes should be considered. Other studies have found that between 17% and 30% of patients with type 2 diabetes have microalbuminuria.^1,12,13 Although primary care physicians report that they provide microalbuminuria screening to a large percentage of their patients with diabetes, in fact only a small percentage of those who should be screened actually are screened.¹⁰ Suboptimal screening rates for important conditions seen in primary care are not unique for microalbuminuria. Other studies have documented comparable low screening rates for a wide variety of cancers.¹⁴ Since physicians do not screen reliably for potentially fatal diseases with screening modalities that have been available for decades, it is unlikely that their behavior is likely to improve when asked to screen for microalbuminuria.

Also, recent evidence that ACEI therapy may improve endothelial function in patients with type 2 diabetes suggests that even patients without microalbuminuria may benefit from routine ACEI therapy.¹⁵ Other studies suggest that routine use of ACEIs in middle-aged patients with type 2 diabetes may provide substantial benefits at only modest costs compared with a screening strategy.¹⁶ These data suggest that a more effective strategy would be to advise that all patients with type 2 diabetes start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while assuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. However, using this strategy, patients who may not have proteinuria will have to take the medication for a prolonged period, pay for it, and run the risks for any complications associated with using the drug.

Limitations

Our study has several limitations. Only 1 practice was examined, and it was part of a residency training practice. This means that less-experienced clinicians were providing care that could reduce the overall rate of screening. However, the rate of screening observed in this study was very similar to rates found in the practices of clinicians with more experience,^11,12 suggesting that the lack of experience of resident physicians may be balanced by the oversight provided by faculty preceptors.

Another limitation is that it was not possible to account for microalbuminuria screening completed outside the MUSC medical center. Patients who split their care among several providers could have had testing performed in other health care facilities. However, since more than 95% of the referrals from the MUSC Family Medicine Center stay within the university health care system, it is doubtful that many patients would have received testing outside the search capabilities of the hospital laboratory database.

Finally, the study was limited in its power to detect small differences between the groups. We originally conceived our project as an exploratory study to determine how many patients were already taking ACEIs and the potential effect of this on overall screening rates for microalbuminuria. Without any reference for the percentage of patients who were taking ACEIs, we could not perform an ad hoc power analysis. However, a post hoc analysis shows that for a sample in which the groups are matched in a 1-to-3 ratio (approximating the proportion of the 51 patients in our sample taking ACEIs and the 183 not taking these drugs) and given the study sample size, our study had a power of 80% to detect a difference in screening rates between 20% in the baseline group and 5% in the ACE or ARB groups. The actual difference seen in our study was much smaller, which increases the possibility of a type II error.

Conclusions

Because physician use of microalbuminuria screening does not follow established guidelines, consideration should be given to other strategies to prevent nephropathy in persons with type 2 diabetes. One proposed strategy would advise all patients with type 2 diabetes to start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while ensuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. It is unknown, however, whether patients would accept universal treatment rather than periodic screening. This is an important question that should be addressed before any population-based strategies are adopted.