Antibiotic Prescribing Model
Univariate analysis revealed that those patients 18 years and older (odds ratio [OR] =3.4; 95% confidence interval [CI], 2.0-5.7), seen in urgent care clinics (OR=1.7; 95% CI, 1.0-2.9), evaluated by a nurse practitioner (OR=5.9; 95% CI, 1.8-19.9), and sick for more than 14 days (OR=4.3; 95% CI=2.0-9.3) were more likely to be treated with an antibiotic Table 1. Antibiotic prescribing was much more frequent for those patients judged by the clinician to be moderately or very likely to have an adverse outcome compared with those judged unlikely or very unlikely to have an adverse outcome if not treated with an antibiotic (OR=61.8; 95% CI, 24.6-155). Table 2 and Table 3 summarize symptoms and signs associated with antibiotic prescribing. Antibiotic prescribing was modestly associated with a number of symptoms and signs Table 4 and much more common for patients with the physical findings of discolored nasal discharge (OR=20.4), sinus tenderness (OR=15.9), a wet cough (OR=8.6), and rales or rhonchi (OR=7.7). After controlling for confounding with logistic regression, 5 variables were independently associated with antibiotic prescribing: sinus tenderness (OR=20.0), rales/ronchi (OR=19.9), yellow/green nasal discharge (OR=11.7), and postnasal drainage (OR=3.1), and negatively associated with clear nasal discharge (OR=0.3).
Patient Expectations Model
An antibiotic was expected by 290 (60%) of the patients with a URI, bronchitis, or sinusitis. A majority of the patients (68%) had received an antibiotic for a similar illness in the past, and 299 (86%) of these patients believed the antibiotic helped. Patients expecting an antibiotic were more likely to receive one Table 5. Patients were more likely to expect an antibiotic who reported green or yellow nasal discharge (OR=2.0; 95% CI, 1.2-3.2), cough productive of yellow or green phlegm (OR=1.7; 95% CI, 1.1-2.5), pain over the eye or cheek (OR=1.6; 95% CI, 1.1-2.4), or who were helped by an antibiotic for similar symptoms in the past (OR=4.5; 95% CI, 2.9-6.9). However, only “helped by an antibiotic for similar symptoms in the past” remained significantly and independently associated with patient expectation after controlling for confounding by logistic regression.
Clinicians believed 298 patients (62%) expected an antibiotic, and they were significantly more likely to prescribe an antibiotic for those patients (OR=4.7; 95% CI, 3.2-7.1) on univariate analysis. The clinicians’ accuracy in predicting which patients expected antibiotics Table 6 was only fair (Cohen’s k=0.21). After controlling for confounding with logistic regression, patient expectation and clinician belief that the patient expected an antibiotic were not independent predictors of antibiotic prescribing. There were no significant differences in the demographic, symptomatic, and diagnostic variables between those records included in the analysis and those records excluded because of incomplete data, implausible data, or lack of informed consent. An analysis restricted to those records with every field completed and with plausible values did not change the final logistic regression models.
Secondary Factors
Clinicians reported that secondary factors contributed to the decision to prescribe an antibiotic for 95% of the patients. The most common reasons were: patient not improving (21%), patient getting worse (19%), and patient has been sick too long (19%). Other secondary reasons included: patient smokes (11%), patient has chronic lung disease (7%), patient expected an antibiotic (6%), patient was quite ill (5%), patient had a comorbid condition other than chronic lung disease (4%), patient was leaving town (2%), and patient requested an antibiotic (2%).
Discussion
Our study suggests that antibiotic prescribing for patients with the clinical diagnoses of URI, bronchitis, or sinusitis is determined by 2 general sets of factors: a small number of physical findings and clinicians’ perceptions of the clinical course of the illness. The physical findings are rales, rhonchi, sinus tenderness, postnasal drainage, purulent nasal discharge, and clear nasal discharge (a negative association). These findings were associated with antibiotic prescribing regardless of the diagnosis the clinician assigned. Notably absent from this list is cough, which was reported by more than 70% of patients assigned any of the 3 diagnoses. Apparently cough alone, which is the chief complaint in many cases of acute respiratory infection, is often not sufficient for clinicians to prescribe antibiotics. In our study, clinicians readily admitted that factors other than the diagnoses contributed to their decisions to prescribe antibiotics. In 95% of the cases, they listed a secondary reason. The majority of these reasons (59%) had to do with the clinical course of the illness: patient not improving (21%), patient getting worse (19%), and patient being sick too long (19%). For patients with the diagnosis of nonspecific URI, clinicians listed one of these reasons for 83% of cases. Whether any of these are legitimate reasons for prescribing antibiotics for acute respiratory infections has not been investigated. Similarly, when clinicians believed that patients were likely to have an adverse outcome if not treated with an antibiotic, they prescribed antibiotics in 98% of cases. This most likely reflects clinicians’ belief that acute sinusitis and acute bronchitis do not improve without antibiotics, a belief largely unsupported by the medical literature.