Does acute bronchitis really exist?

Acute bronchitis and upper respiratory infections (URIs) represent 2 of the most common diagnoses made by primary care physicians.^1,2 It is frequently difficult for clinicians to differentiate between these conditions, since a considerable amount of overlap exists. This confusion is similar to our previous findings that URIs and sinusitis are very similar in their clinical presentation.³

As we observed with sinusitis, it is possible that the diagnosis of acute bronchitis is made primarily to justify treatment decisions. A study of children suggests that the diagnosis of bronchitis may depend on a physician’s desire to justify antibiotic treatment.⁴ Although antibiotics are of only minimal benefit at best to bronchitis patients,^5-7 data from a variety of studies demonstrate that physicians prescribe antibiotics for bronchitis at much higher rates than for URIs.^8,9

Four previous studies have provided some indication of clinicians’ opinions about what signs and symptoms constitute acute bronchitis. However, those studies reveal divergent opinions among primary care physicians. For example, in a survey of family physicians concerning what criteria was used to make the diagnosis of acute bronchitis, Oeffinger and colleagues¹⁰ found that 58% of physicians made the diagnosis of acute bronchitis only if the patient had a productive cough; 39%, however, stated that whether the cough was productive did not influence their diagnosis. A similar survey of physicians in the Netherlands suggested that clinicians did not rely on any specific sign or symptom but instead relied on the total number of symptoms to define acute bronchitis.¹¹ This implies that the conditions may not be different and that acute bronchitis may really be a “bad cold.” Our work suggests that most physicians diagnosed simulated cases as acute bronchitis and treated them with antibiotics if the sputum had some discoloration,¹² a finding that represents inflammation and is not predictive of antibiotic response.¹³ A previous study that examined clinicians’ reports from patient encounters suggested that patients thought to have acute bronchitis were more likely to have a productive cough, purulent sputum, and abnormal findings on lung examination.¹⁴ However, the study had fewer than 50 patients (29 with bronchitis and 19 with upper respiratory tract infection) and was completed before much of the information on the lack of benefit from antibiotics was reported.

The purpose of our study was to explore whether any clinical signs and symptoms predict the diagnosis of acute bronchitis rather than URI. We hypothesized that these 2 conditions would have few clinical differences and that the patients with acute bronchitis would differ from those with URI primarily on the basis of treatments rendered rather than clinical presentation. This would support the hypothesis that acute bronchitis and the common cold constitute the same clinical condition, differing only in the severity of cough and the desire for a condition amenable to treatment.

Methods

We selected subjects for this study from the population of patients who presented for care at the Department of Family Medicine at the Medical University of South Carolina. Two clinical sites for the department serve approximately 48,000 ambulatory patient encounters each year. The Department of Family Medicine uses family practice residents, physician faculty, nurse practitioners, and physician assistants to provide patient care. The design of the study was a case-control model with acute bronchitis patients representing cases and URI patients serving as control subjects.

To identify patients with URIs and acute bronchitis, we used International Classification of Diseases-ninth revision-Clinical Modification (ICD-9-CM) codes for acute bronchitis and URI that were entered with the diagnosis recorded in the electronic medical record. A search for all patients with a problem code 466.0 for acute bronchitis between June 1, 1996, and December 31, 1998, found 165 patient records. Using a similar approach and the ICD-9 code 465.9 for upper respiratory infection, we identified 526 patients with a diagnosis of URI in the same time period. We selected a random sample of 495 records to create a 3:1 match with the bronchitis cases. Patient visits that contained a secondary diagnosis of otitis media, sinusitis, asthma, chronic obstructive pulmonary disease, congestive heart failure, or pneumonia were excluded. The remaining number of total records was 544 (409 URI and 135 acute bronchitis).

Two medical students conducted a detailed chart review of these records. Information on demographics, symptoms, and physical findings were recorded, as well as the provider’s level of training for each record reviewed. To assess the interrater reliability of the reviewers, a random sample of 54 charts (10% of the total sample) was abstracted by both reviewers. Interrater agreement was excellent, ranging from 93% to 100%, depending on the variable.

Information was entered into Epi Info, version 6 (Centers for Disease Control, Atlanta, Ga), a standard epidemiologic database. Data were analyzed with bivariate comparisons of possible predictors. From the initial analysis, the statistically significant variables most often associated with either URI or acute bronchitis were used to perform a multiple regression to determine the independent predictive value of these variables. Regression analysis was performed using True Epistat software (Epistat Services, Richardson, Tex). Because of the large number of variables used in the study (4 demographic, 11 symptom, and 9 physical finding variables), we used the Bonferroni adjustment for multiple comparisons and adjusted the P value for 24 multiple comparisons to set a value of 0.002 (0.05 of 24 possible comparisons) as the indicator of statistical significance.¹⁴

Results

Table 1 shows the demographics and recent visit history for patients based on their diagnosis. Acute bronchitis patients were slightly older than those with URIs and were more likely to be smokers. Acute bronchitis patients also were more likely to have made previous visits for either URI or acute bronchitis within 3 months of the diagnosis. When we examined the training level of physicians who saw these patients, we found that attending physicians were more likely to diagnose acute bronchitis than were residents. Of the patients seen by attending physicians, 33% were were considered to have acute bronchitis, compared with 19% of the patients seen by residents (P <.001). Examining the reported symptoms of those patients with acute bronchitis and URI revealed that several symptoms were more often associated with each diagnosis Table 2. Cough was present in the majority of both conditions but occurred more often when acute bronchitis was the diagnosis. Chest pain, shortness of breath, and a history of wheezing also were associated with acute bronchitis, although each was present in only 8% to 12% of the cases. In contrast, symptoms associated with URI included runny nose and sore throat, but neither alone was seen in a majority of patients considered to have URIs.

Comparisons of physical findings provided similar results Table 3. A red throat, red nose, or cervical lymph nodes were all associated with the diagnosis of URI. The only physical finding associated with bronchitis was the presence of wheezing, found in approximately 30% of patients with acute bronchitis.

Since very few of the symptoms and physical findings associated with the diagnosis of acute bronchitis or URI appeared in the majority of patients, it was thought that clinicians probably rely on a constellation of these signs and symptoms to make the diagnosis of bronchitis. Also, because each of the symptoms and signs might not be independent predictors of URI as opposed to bronchitis, we entered symptoms and physical findings associated with each diagnosis into a multivariate logistic regression model along with possible demographic predictors. Table 4 shows the results of this logistic regression. All other things being equal, cough and wheezing were the strongest independent predictors of acute bronchitis, while nausea or a red or runny nose were the strongest predictors of URI. Also of note is that adults and patients who had been seen in the previous 3 months with bronchitis were more likely to receive a diagnosis of acute bronchitis independent of their other signs and symptoms.

The logistic regression model had an R2 of 0.37, indicating that all the signs and symptom variables that we considered explained only approximately a third of the differences between these 2 conditions. To illustrate the limitations of using just these 2 variables to differentiate acute bronchitis and URI, if the presence of a cough was used as the sole determinant of the diagnosis, the sensitivity for acute bronchitis would be 98% (132 out of 135), but specificity would be only 29% (120 out of 409). Wheezing on its own had a sensitivity of 30% with a specificity of 97%. Adding in the absence of runny nose or nausea to these other predictors was no better than wheezing alone. Leaving out wheezing and including cough, absence of runny nose, and nausea gave a sensitivity of 82% with a specificity of 65%. Thus, clinical factors alone are insufficient to explain why some patients were given the diagnosis they received.

We also explored whether clinicians used a diagnosis to influence treatment decisions. It appeared that treatments did differ according to the diagnosis. Patients with acute bronchitis were 8 times more likely to receive a bronchodilator than those with a URI (70% vs 8%, P <.001) and were more likely to receive antibiotics (26% vs 4%, P <.001). Decongestants ere prescribed more often when the diagnosis was a URI (33% vs 16%, P <.001).

Discussion

Our study demonstrates that physicians rely on only a few clinical factors to differentiate acute bronchitis from URI. These factors are poor predictors of which patients will receive a diagnosis of acute bronchitis and which URI, since significant overlap exists between these 2 disorders. Despite a lack of clear differences between these conditions, physicians use these diagnoses to make treatment decisions. The low degree of specificity for clinical signs and symptoms in differentiating the 2 conditions implies that physicians use other cues such as the patient’s desire for treatment, personal thresholds for prescribing, and a general gestalt when labeling the condition.

These findings mirror our previous study that shows significant clinical overlap between sinusitis and URI.³ As in our current findings with acute bronchitis, “sinusitis” may simply be an acute respiratory infection predominantly in the head with moderate to high severity. Computed tomography scans of patients with clinical syndromes diagnosed as “colds” show sinus inflammation in 47% of patients.¹⁶ The condition frequently labeled as “sinusitis” may constitute a desire of physicians to use antibiotics to treat symptoms caused by this virally induced inflammation, even though scant evidence exists that antibiotics improve outcomes even when sinusitis is demonstrated by radiologic techniques. In most clinical situations, a majority of patients, clinicians, and clinical pharmacists appear to assign the diagnosis of sinusitis or believe antibiotics are helpful for any respiratory infection with discolored nasal discharge.^12,17,18 However, discolored discharge on its own is a poor predictor of antibiotic response and is a common manifestation of a URI.

The same situation seems to exist with acute bronchitis. Acute bronchitis may be nothing more than an acute respiratory infection that is predominantly in the chest. This would explain why there is such a high degree of overlap between the signs and symptoms of this condition and illnesses labeled as URIs. Except for the observation that albuterol is effective at hastening symptom resolution in patients with productive coughs and wheezes^19,20 but ineffective for patients with nonspecific coughs associated with upper airway symptoms,²¹ there is little value in labeling patients as having acute bronchitis rather than a cold, since these 2 entities are probably manifestations of the same clinical condition.

Taken together, it may be more useful to reconceptualize respiratory infections as a single clinical entity rather than by anatomically specific diagnoses. Patients may differ in the degree of severity of the illness and the anatomic area that produces most of their complaints. Clinically and in our research, we may be better served by representing all viral respiratory conditions as a single clinical diagnosis with severity and anatomic indications. All patients with acute symptoms involving the sinuses, nose, pharynx, and bronchial tree could be labeled as having an “acute respiratory infection,” either “sinus predominant,” “bronchial predominant,” or even “generalized” when involving all areas of the respiratory tract.

Most evidence suggests that the vast majority of all these infections are caused by viruses. This does not imply that patients do not have infections and are not ill. Not only do viruses vary in the degree in which they infect individuals, but patients also differ in their abilities to cope with their cold symptoms. Rather than attempting to eradicate the cause of the cold, the goals of treatment for these disorders should be improving outcomes that matter to patients, such as reducing their symptoms, improving their ability to function at work and at home, and relieving their anxiety. Instead of trying to eradicate bacteria that do not exist in the majority of patients, physicians should focus on treatments proven to alleviate the predominant symptoms and the underlying reasons patients seek care for this self-limited problem. These latter reasons could include loneliness, anxiety about the severity of the condition (for example, in a young child), or frustration that the symptoms are interrupting other important activities. Attention to these important psychosocial events may be even more important than the type of drug written on the prescription pad. Dismissing a patient with these problems as being uninformed, bothersome, or inappropriately seeking care may not be productive in addressing the underlying reasons the patient has consulted a physician. Failing to address these underlying psychosocial issues or prescribing an antibiotic to meet physicians’ desire to help and meet an unstated patient expectation may result in repetitive care-seeking for the same self-limited symptoms,^22,23 ultimately benefiting no one and consuming health care resources that could be better invested elsewhere.

This new model of conceptualizing respiratory infections implies that assigning an anatomic-specific diagnosis to the condition is irrelevant beyond being a determinant for which symptomatic care should be the highest priority (eg, decongestants for predominantly sinus symptoms or bronchodilators for wheezing or rhonchi). Also, although acute respiratory infection is a very common reason for visits to primary care physicians, only some patients consult a clinician for their problem. Care-seeking for acute respiratory infection is likely determined by a combination of forces that include severity of the infection (patients with more severe viral illnesses would be more likely to seek care), anatomic localization (infections with more specifically localized symptoms would be more likely to seek care), and personal psychosocial issues (including the perceived importance of existing or possible disruption of daily activities, personal coping skills and resources, and the need for empathy and affirmation from someone else that they are sick). Rather than focusing research in this area on identifying how certain subsets of patients with what is predominantly a viral illness respond to antibiotics that do not treat what they have, future research in acute respiratory infections might be better directed at why some patients seek care or self-medicate inappropriately²⁴ and how clinicians can best serve this population.

Conclusions

Our study shows a great deal of overlap in the signs and symptoms of acute bronchitis and URIs. Very little of the variation in the diagnoses could be explained by clinical factors. These results are similar to earlier work suggesting considerable clinical overlap in sinusitis. This leads us to hypothesize that these conditions all represent the same clinical entity and that a reconceptualization of acute viral respiratory infections as a single problem, rather than anatomically distinct disorders, is warranted.

Acute bronchitis and upper respiratory infections (URIs) represent 2 of the most common diagnoses made by primary care physicians.^1,2 It is frequently difficult for clinicians to differentiate between these conditions, since a considerable amount of overlap exists. This confusion is similar to our previous findings that URIs and sinusitis are very similar in their clinical presentation.³

As we observed with sinusitis, it is possible that the diagnosis of acute bronchitis is made primarily to justify treatment decisions. A study of children suggests that the diagnosis of bronchitis may depend on a physician’s desire to justify antibiotic treatment.⁴ Although antibiotics are of only minimal benefit at best to bronchitis patients,^5-7 data from a variety of studies demonstrate that physicians prescribe antibiotics for bronchitis at much higher rates than for URIs.^8,9

Four previous studies have provided some indication of clinicians’ opinions about what signs and symptoms constitute acute bronchitis. However, those studies reveal divergent opinions among primary care physicians. For example, in a survey of family physicians concerning what criteria was used to make the diagnosis of acute bronchitis, Oeffinger and colleagues¹⁰ found that 58% of physicians made the diagnosis of acute bronchitis only if the patient had a productive cough; 39%, however, stated that whether the cough was productive did not influence their diagnosis. A similar survey of physicians in the Netherlands suggested that clinicians did not rely on any specific sign or symptom but instead relied on the total number of symptoms to define acute bronchitis.¹¹ This implies that the conditions may not be different and that acute bronchitis may really be a “bad cold.” Our work suggests that most physicians diagnosed simulated cases as acute bronchitis and treated them with antibiotics if the sputum had some discoloration,¹² a finding that represents inflammation and is not predictive of antibiotic response.¹³ A previous study that examined clinicians’ reports from patient encounters suggested that patients thought to have acute bronchitis were more likely to have a productive cough, purulent sputum, and abnormal findings on lung examination.¹⁴ However, the study had fewer than 50 patients (29 with bronchitis and 19 with upper respiratory tract infection) and was completed before much of the information on the lack of benefit from antibiotics was reported.

The purpose of our study was to explore whether any clinical signs and symptoms predict the diagnosis of acute bronchitis rather than URI. We hypothesized that these 2 conditions would have few clinical differences and that the patients with acute bronchitis would differ from those with URI primarily on the basis of treatments rendered rather than clinical presentation. This would support the hypothesis that acute bronchitis and the common cold constitute the same clinical condition, differing only in the severity of cough and the desire for a condition amenable to treatment.

Methods

We selected subjects for this study from the population of patients who presented for care at the Department of Family Medicine at the Medical University of South Carolina. Two clinical sites for the department serve approximately 48,000 ambulatory patient encounters each year. The Department of Family Medicine uses family practice residents, physician faculty, nurse practitioners, and physician assistants to provide patient care. The design of the study was a case-control model with acute bronchitis patients representing cases and URI patients serving as control subjects.

To identify patients with URIs and acute bronchitis, we used International Classification of Diseases-ninth revision-Clinical Modification (ICD-9-CM) codes for acute bronchitis and URI that were entered with the diagnosis recorded in the electronic medical record. A search for all patients with a problem code 466.0 for acute bronchitis between June 1, 1996, and December 31, 1998, found 165 patient records. Using a similar approach and the ICD-9 code 465.9 for upper respiratory infection, we identified 526 patients with a diagnosis of URI in the same time period. We selected a random sample of 495 records to create a 3:1 match with the bronchitis cases. Patient visits that contained a secondary diagnosis of otitis media, sinusitis, asthma, chronic obstructive pulmonary disease, congestive heart failure, or pneumonia were excluded. The remaining number of total records was 544 (409 URI and 135 acute bronchitis).

Two medical students conducted a detailed chart review of these records. Information on demographics, symptoms, and physical findings were recorded, as well as the provider’s level of training for each record reviewed. To assess the interrater reliability of the reviewers, a random sample of 54 charts (10% of the total sample) was abstracted by both reviewers. Interrater agreement was excellent, ranging from 93% to 100%, depending on the variable.

Information was entered into Epi Info, version 6 (Centers for Disease Control, Atlanta, Ga), a standard epidemiologic database. Data were analyzed with bivariate comparisons of possible predictors. From the initial analysis, the statistically significant variables most often associated with either URI or acute bronchitis were used to perform a multiple regression to determine the independent predictive value of these variables. Regression analysis was performed using True Epistat software (Epistat Services, Richardson, Tex). Because of the large number of variables used in the study (4 demographic, 11 symptom, and 9 physical finding variables), we used the Bonferroni adjustment for multiple comparisons and adjusted the P value for 24 multiple comparisons to set a value of 0.002 (0.05 of 24 possible comparisons) as the indicator of statistical significance.¹⁴

Results

Table 1 shows the demographics and recent visit history for patients based on their diagnosis. Acute bronchitis patients were slightly older than those with URIs and were more likely to be smokers. Acute bronchitis patients also were more likely to have made previous visits for either URI or acute bronchitis within 3 months of the diagnosis. When we examined the training level of physicians who saw these patients, we found that attending physicians were more likely to diagnose acute bronchitis than were residents. Of the patients seen by attending physicians, 33% were were considered to have acute bronchitis, compared with 19% of the patients seen by residents (P <.001). Examining the reported symptoms of those patients with acute bronchitis and URI revealed that several symptoms were more often associated with each diagnosis Table 2. Cough was present in the majority of both conditions but occurred more often when acute bronchitis was the diagnosis. Chest pain, shortness of breath, and a history of wheezing also were associated with acute bronchitis, although each was present in only 8% to 12% of the cases. In contrast, symptoms associated with URI included runny nose and sore throat, but neither alone was seen in a majority of patients considered to have URIs.

Comparisons of physical findings provided similar results Table 3. A red throat, red nose, or cervical lymph nodes were all associated with the diagnosis of URI. The only physical finding associated with bronchitis was the presence of wheezing, found in approximately 30% of patients with acute bronchitis.

Since very few of the symptoms and physical findings associated with the diagnosis of acute bronchitis or URI appeared in the majority of patients, it was thought that clinicians probably rely on a constellation of these signs and symptoms to make the diagnosis of bronchitis. Also, because each of the symptoms and signs might not be independent predictors of URI as opposed to bronchitis, we entered symptoms and physical findings associated with each diagnosis into a multivariate logistic regression model along with possible demographic predictors. Table 4 shows the results of this logistic regression. All other things being equal, cough and wheezing were the strongest independent predictors of acute bronchitis, while nausea or a red or runny nose were the strongest predictors of URI. Also of note is that adults and patients who had been seen in the previous 3 months with bronchitis were more likely to receive a diagnosis of acute bronchitis independent of their other signs and symptoms.

The logistic regression model had an R2 of 0.37, indicating that all the signs and symptom variables that we considered explained only approximately a third of the differences between these 2 conditions. To illustrate the limitations of using just these 2 variables to differentiate acute bronchitis and URI, if the presence of a cough was used as the sole determinant of the diagnosis, the sensitivity for acute bronchitis would be 98% (132 out of 135), but specificity would be only 29% (120 out of 409). Wheezing on its own had a sensitivity of 30% with a specificity of 97%. Adding in the absence of runny nose or nausea to these other predictors was no better than wheezing alone. Leaving out wheezing and including cough, absence of runny nose, and nausea gave a sensitivity of 82% with a specificity of 65%. Thus, clinical factors alone are insufficient to explain why some patients were given the diagnosis they received.

We also explored whether clinicians used a diagnosis to influence treatment decisions. It appeared that treatments did differ according to the diagnosis. Patients with acute bronchitis were 8 times more likely to receive a bronchodilator than those with a URI (70% vs 8%, P <.001) and were more likely to receive antibiotics (26% vs 4%, P <.001). Decongestants ere prescribed more often when the diagnosis was a URI (33% vs 16%, P <.001).

Discussion

Our study demonstrates that physicians rely on only a few clinical factors to differentiate acute bronchitis from URI. These factors are poor predictors of which patients will receive a diagnosis of acute bronchitis and which URI, since significant overlap exists between these 2 disorders. Despite a lack of clear differences between these conditions, physicians use these diagnoses to make treatment decisions. The low degree of specificity for clinical signs and symptoms in differentiating the 2 conditions implies that physicians use other cues such as the patient’s desire for treatment, personal thresholds for prescribing, and a general gestalt when labeling the condition.

These findings mirror our previous study that shows significant clinical overlap between sinusitis and URI.³ As in our current findings with acute bronchitis, “sinusitis” may simply be an acute respiratory infection predominantly in the head with moderate to high severity. Computed tomography scans of patients with clinical syndromes diagnosed as “colds” show sinus inflammation in 47% of patients.¹⁶ The condition frequently labeled as “sinusitis” may constitute a desire of physicians to use antibiotics to treat symptoms caused by this virally induced inflammation, even though scant evidence exists that antibiotics improve outcomes even when sinusitis is demonstrated by radiologic techniques. In most clinical situations, a majority of patients, clinicians, and clinical pharmacists appear to assign the diagnosis of sinusitis or believe antibiotics are helpful for any respiratory infection with discolored nasal discharge.^12,17,18 However, discolored discharge on its own is a poor predictor of antibiotic response and is a common manifestation of a URI.

The same situation seems to exist with acute bronchitis. Acute bronchitis may be nothing more than an acute respiratory infection that is predominantly in the chest. This would explain why there is such a high degree of overlap between the signs and symptoms of this condition and illnesses labeled as URIs. Except for the observation that albuterol is effective at hastening symptom resolution in patients with productive coughs and wheezes^19,20 but ineffective for patients with nonspecific coughs associated with upper airway symptoms,²¹ there is little value in labeling patients as having acute bronchitis rather than a cold, since these 2 entities are probably manifestations of the same clinical condition.

Taken together, it may be more useful to reconceptualize respiratory infections as a single clinical entity rather than by anatomically specific diagnoses. Patients may differ in the degree of severity of the illness and the anatomic area that produces most of their complaints. Clinically and in our research, we may be better served by representing all viral respiratory conditions as a single clinical diagnosis with severity and anatomic indications. All patients with acute symptoms involving the sinuses, nose, pharynx, and bronchial tree could be labeled as having an “acute respiratory infection,” either “sinus predominant,” “bronchial predominant,” or even “generalized” when involving all areas of the respiratory tract.

Most evidence suggests that the vast majority of all these infections are caused by viruses. This does not imply that patients do not have infections and are not ill. Not only do viruses vary in the degree in which they infect individuals, but patients also differ in their abilities to cope with their cold symptoms. Rather than attempting to eradicate the cause of the cold, the goals of treatment for these disorders should be improving outcomes that matter to patients, such as reducing their symptoms, improving their ability to function at work and at home, and relieving their anxiety. Instead of trying to eradicate bacteria that do not exist in the majority of patients, physicians should focus on treatments proven to alleviate the predominant symptoms and the underlying reasons patients seek care for this self-limited problem. These latter reasons could include loneliness, anxiety about the severity of the condition (for example, in a young child), or frustration that the symptoms are interrupting other important activities. Attention to these important psychosocial events may be even more important than the type of drug written on the prescription pad. Dismissing a patient with these problems as being uninformed, bothersome, or inappropriately seeking care may not be productive in addressing the underlying reasons the patient has consulted a physician. Failing to address these underlying psychosocial issues or prescribing an antibiotic to meet physicians’ desire to help and meet an unstated patient expectation may result in repetitive care-seeking for the same self-limited symptoms,^22,23 ultimately benefiting no one and consuming health care resources that could be better invested elsewhere.

This new model of conceptualizing respiratory infections implies that assigning an anatomic-specific diagnosis to the condition is irrelevant beyond being a determinant for which symptomatic care should be the highest priority (eg, decongestants for predominantly sinus symptoms or bronchodilators for wheezing or rhonchi). Also, although acute respiratory infection is a very common reason for visits to primary care physicians, only some patients consult a clinician for their problem. Care-seeking for acute respiratory infection is likely determined by a combination of forces that include severity of the infection (patients with more severe viral illnesses would be more likely to seek care), anatomic localization (infections with more specifically localized symptoms would be more likely to seek care), and personal psychosocial issues (including the perceived importance of existing or possible disruption of daily activities, personal coping skills and resources, and the need for empathy and affirmation from someone else that they are sick). Rather than focusing research in this area on identifying how certain subsets of patients with what is predominantly a viral illness respond to antibiotics that do not treat what they have, future research in acute respiratory infections might be better directed at why some patients seek care or self-medicate inappropriately²⁴ and how clinicians can best serve this population.

Conclusions

Our study shows a great deal of overlap in the signs and symptoms of acute bronchitis and URIs. Very little of the variation in the diagnoses could be explained by clinical factors. These results are similar to earlier work suggesting considerable clinical overlap in sinusitis. This leads us to hypothesize that these conditions all represent the same clinical entity and that a reconceptualization of acute viral respiratory infections as a single problem, rather than anatomically distinct disorders, is warranted.

Acute bronchitis and upper respiratory infections (URIs) represent 2 of the most common diagnoses made by primary care physicians.^1,2 It is frequently difficult for clinicians to differentiate between these conditions, since a considerable amount of overlap exists. This confusion is similar to our previous findings that URIs and sinusitis are very similar in their clinical presentation.³

As we observed with sinusitis, it is possible that the diagnosis of acute bronchitis is made primarily to justify treatment decisions. A study of children suggests that the diagnosis of bronchitis may depend on a physician’s desire to justify antibiotic treatment.⁴ Although antibiotics are of only minimal benefit at best to bronchitis patients,^5-7 data from a variety of studies demonstrate that physicians prescribe antibiotics for bronchitis at much higher rates than for URIs.^8,9

Four previous studies have provided some indication of clinicians’ opinions about what signs and symptoms constitute acute bronchitis. However, those studies reveal divergent opinions among primary care physicians. For example, in a survey of family physicians concerning what criteria was used to make the diagnosis of acute bronchitis, Oeffinger and colleagues¹⁰ found that 58% of physicians made the diagnosis of acute bronchitis only if the patient had a productive cough; 39%, however, stated that whether the cough was productive did not influence their diagnosis. A similar survey of physicians in the Netherlands suggested that clinicians did not rely on any specific sign or symptom but instead relied on the total number of symptoms to define acute bronchitis.¹¹ This implies that the conditions may not be different and that acute bronchitis may really be a “bad cold.” Our work suggests that most physicians diagnosed simulated cases as acute bronchitis and treated them with antibiotics if the sputum had some discoloration,¹² a finding that represents inflammation and is not predictive of antibiotic response.¹³ A previous study that examined clinicians’ reports from patient encounters suggested that patients thought to have acute bronchitis were more likely to have a productive cough, purulent sputum, and abnormal findings on lung examination.¹⁴ However, the study had fewer than 50 patients (29 with bronchitis and 19 with upper respiratory tract infection) and was completed before much of the information on the lack of benefit from antibiotics was reported.

The purpose of our study was to explore whether any clinical signs and symptoms predict the diagnosis of acute bronchitis rather than URI. We hypothesized that these 2 conditions would have few clinical differences and that the patients with acute bronchitis would differ from those with URI primarily on the basis of treatments rendered rather than clinical presentation. This would support the hypothesis that acute bronchitis and the common cold constitute the same clinical condition, differing only in the severity of cough and the desire for a condition amenable to treatment.

Methods

We selected subjects for this study from the population of patients who presented for care at the Department of Family Medicine at the Medical University of South Carolina. Two clinical sites for the department serve approximately 48,000 ambulatory patient encounters each year. The Department of Family Medicine uses family practice residents, physician faculty, nurse practitioners, and physician assistants to provide patient care. The design of the study was a case-control model with acute bronchitis patients representing cases and URI patients serving as control subjects.

To identify patients with URIs and acute bronchitis, we used International Classification of Diseases-ninth revision-Clinical Modification (ICD-9-CM) codes for acute bronchitis and URI that were entered with the diagnosis recorded in the electronic medical record. A search for all patients with a problem code 466.0 for acute bronchitis between June 1, 1996, and December 31, 1998, found 165 patient records. Using a similar approach and the ICD-9 code 465.9 for upper respiratory infection, we identified 526 patients with a diagnosis of URI in the same time period. We selected a random sample of 495 records to create a 3:1 match with the bronchitis cases. Patient visits that contained a secondary diagnosis of otitis media, sinusitis, asthma, chronic obstructive pulmonary disease, congestive heart failure, or pneumonia were excluded. The remaining number of total records was 544 (409 URI and 135 acute bronchitis).

Two medical students conducted a detailed chart review of these records. Information on demographics, symptoms, and physical findings were recorded, as well as the provider’s level of training for each record reviewed. To assess the interrater reliability of the reviewers, a random sample of 54 charts (10% of the total sample) was abstracted by both reviewers. Interrater agreement was excellent, ranging from 93% to 100%, depending on the variable.

Information was entered into Epi Info, version 6 (Centers for Disease Control, Atlanta, Ga), a standard epidemiologic database. Data were analyzed with bivariate comparisons of possible predictors. From the initial analysis, the statistically significant variables most often associated with either URI or acute bronchitis were used to perform a multiple regression to determine the independent predictive value of these variables. Regression analysis was performed using True Epistat software (Epistat Services, Richardson, Tex). Because of the large number of variables used in the study (4 demographic, 11 symptom, and 9 physical finding variables), we used the Bonferroni adjustment for multiple comparisons and adjusted the P value for 24 multiple comparisons to set a value of 0.002 (0.05 of 24 possible comparisons) as the indicator of statistical significance.¹⁴

Results

Table 1 shows the demographics and recent visit history for patients based on their diagnosis. Acute bronchitis patients were slightly older than those with URIs and were more likely to be smokers. Acute bronchitis patients also were more likely to have made previous visits for either URI or acute bronchitis within 3 months of the diagnosis. When we examined the training level of physicians who saw these patients, we found that attending physicians were more likely to diagnose acute bronchitis than were residents. Of the patients seen by attending physicians, 33% were were considered to have acute bronchitis, compared with 19% of the patients seen by residents (P <.001). Examining the reported symptoms of those patients with acute bronchitis and URI revealed that several symptoms were more often associated with each diagnosis Table 2. Cough was present in the majority of both conditions but occurred more often when acute bronchitis was the diagnosis. Chest pain, shortness of breath, and a history of wheezing also were associated with acute bronchitis, although each was present in only 8% to 12% of the cases. In contrast, symptoms associated with URI included runny nose and sore throat, but neither alone was seen in a majority of patients considered to have URIs.

Comparisons of physical findings provided similar results Table 3. A red throat, red nose, or cervical lymph nodes were all associated with the diagnosis of URI. The only physical finding associated with bronchitis was the presence of wheezing, found in approximately 30% of patients with acute bronchitis.

Since very few of the symptoms and physical findings associated with the diagnosis of acute bronchitis or URI appeared in the majority of patients, it was thought that clinicians probably rely on a constellation of these signs and symptoms to make the diagnosis of bronchitis. Also, because each of the symptoms and signs might not be independent predictors of URI as opposed to bronchitis, we entered symptoms and physical findings associated with each diagnosis into a multivariate logistic regression model along with possible demographic predictors. Table 4 shows the results of this logistic regression. All other things being equal, cough and wheezing were the strongest independent predictors of acute bronchitis, while nausea or a red or runny nose were the strongest predictors of URI. Also of note is that adults and patients who had been seen in the previous 3 months with bronchitis were more likely to receive a diagnosis of acute bronchitis independent of their other signs and symptoms.

The logistic regression model had an R2 of 0.37, indicating that all the signs and symptom variables that we considered explained only approximately a third of the differences between these 2 conditions. To illustrate the limitations of using just these 2 variables to differentiate acute bronchitis and URI, if the presence of a cough was used as the sole determinant of the diagnosis, the sensitivity for acute bronchitis would be 98% (132 out of 135), but specificity would be only 29% (120 out of 409). Wheezing on its own had a sensitivity of 30% with a specificity of 97%. Adding in the absence of runny nose or nausea to these other predictors was no better than wheezing alone. Leaving out wheezing and including cough, absence of runny nose, and nausea gave a sensitivity of 82% with a specificity of 65%. Thus, clinical factors alone are insufficient to explain why some patients were given the diagnosis they received.

We also explored whether clinicians used a diagnosis to influence treatment decisions. It appeared that treatments did differ according to the diagnosis. Patients with acute bronchitis were 8 times more likely to receive a bronchodilator than those with a URI (70% vs 8%, P <.001) and were more likely to receive antibiotics (26% vs 4%, P <.001). Decongestants ere prescribed more often when the diagnosis was a URI (33% vs 16%, P <.001).

Discussion

Our study demonstrates that physicians rely on only a few clinical factors to differentiate acute bronchitis from URI. These factors are poor predictors of which patients will receive a diagnosis of acute bronchitis and which URI, since significant overlap exists between these 2 disorders. Despite a lack of clear differences between these conditions, physicians use these diagnoses to make treatment decisions. The low degree of specificity for clinical signs and symptoms in differentiating the 2 conditions implies that physicians use other cues such as the patient’s desire for treatment, personal thresholds for prescribing, and a general gestalt when labeling the condition.

These findings mirror our previous study that shows significant clinical overlap between sinusitis and URI.³ As in our current findings with acute bronchitis, “sinusitis” may simply be an acute respiratory infection predominantly in the head with moderate to high severity. Computed tomography scans of patients with clinical syndromes diagnosed as “colds” show sinus inflammation in 47% of patients.¹⁶ The condition frequently labeled as “sinusitis” may constitute a desire of physicians to use antibiotics to treat symptoms caused by this virally induced inflammation, even though scant evidence exists that antibiotics improve outcomes even when sinusitis is demonstrated by radiologic techniques. In most clinical situations, a majority of patients, clinicians, and clinical pharmacists appear to assign the diagnosis of sinusitis or believe antibiotics are helpful for any respiratory infection with discolored nasal discharge.^12,17,18 However, discolored discharge on its own is a poor predictor of antibiotic response and is a common manifestation of a URI.

The same situation seems to exist with acute bronchitis. Acute bronchitis may be nothing more than an acute respiratory infection that is predominantly in the chest. This would explain why there is such a high degree of overlap between the signs and symptoms of this condition and illnesses labeled as URIs. Except for the observation that albuterol is effective at hastening symptom resolution in patients with productive coughs and wheezes^19,20 but ineffective for patients with nonspecific coughs associated with upper airway symptoms,²¹ there is little value in labeling patients as having acute bronchitis rather than a cold, since these 2 entities are probably manifestations of the same clinical condition.

Taken together, it may be more useful to reconceptualize respiratory infections as a single clinical entity rather than by anatomically specific diagnoses. Patients may differ in the degree of severity of the illness and the anatomic area that produces most of their complaints. Clinically and in our research, we may be better served by representing all viral respiratory conditions as a single clinical diagnosis with severity and anatomic indications. All patients with acute symptoms involving the sinuses, nose, pharynx, and bronchial tree could be labeled as having an “acute respiratory infection,” either “sinus predominant,” “bronchial predominant,” or even “generalized” when involving all areas of the respiratory tract.

Most evidence suggests that the vast majority of all these infections are caused by viruses. This does not imply that patients do not have infections and are not ill. Not only do viruses vary in the degree in which they infect individuals, but patients also differ in their abilities to cope with their cold symptoms. Rather than attempting to eradicate the cause of the cold, the goals of treatment for these disorders should be improving outcomes that matter to patients, such as reducing their symptoms, improving their ability to function at work and at home, and relieving their anxiety. Instead of trying to eradicate bacteria that do not exist in the majority of patients, physicians should focus on treatments proven to alleviate the predominant symptoms and the underlying reasons patients seek care for this self-limited problem. These latter reasons could include loneliness, anxiety about the severity of the condition (for example, in a young child), or frustration that the symptoms are interrupting other important activities. Attention to these important psychosocial events may be even more important than the type of drug written on the prescription pad. Dismissing a patient with these problems as being uninformed, bothersome, or inappropriately seeking care may not be productive in addressing the underlying reasons the patient has consulted a physician. Failing to address these underlying psychosocial issues or prescribing an antibiotic to meet physicians’ desire to help and meet an unstated patient expectation may result in repetitive care-seeking for the same self-limited symptoms,^22,23 ultimately benefiting no one and consuming health care resources that could be better invested elsewhere.

This new model of conceptualizing respiratory infections implies that assigning an anatomic-specific diagnosis to the condition is irrelevant beyond being a determinant for which symptomatic care should be the highest priority (eg, decongestants for predominantly sinus symptoms or bronchodilators for wheezing or rhonchi). Also, although acute respiratory infection is a very common reason for visits to primary care physicians, only some patients consult a clinician for their problem. Care-seeking for acute respiratory infection is likely determined by a combination of forces that include severity of the infection (patients with more severe viral illnesses would be more likely to seek care), anatomic localization (infections with more specifically localized symptoms would be more likely to seek care), and personal psychosocial issues (including the perceived importance of existing or possible disruption of daily activities, personal coping skills and resources, and the need for empathy and affirmation from someone else that they are sick). Rather than focusing research in this area on identifying how certain subsets of patients with what is predominantly a viral illness respond to antibiotics that do not treat what they have, future research in acute respiratory infections might be better directed at why some patients seek care or self-medicate inappropriately²⁴ and how clinicians can best serve this population.

Conclusions

Our study shows a great deal of overlap in the signs and symptoms of acute bronchitis and URIs. Very little of the variation in the diagnoses could be explained by clinical factors. These results are similar to earlier work suggesting considerable clinical overlap in sinusitis. This leads us to hypothesize that these conditions all represent the same clinical entity and that a reconceptualization of acute viral respiratory infections as a single problem, rather than anatomically distinct disorders, is warranted.