Antiviral and antibiotic prescribing for influenza in primary care

Abstract

Background: Anti-influenza antiviral medications reduce influenza-related morbidity, but may often be used inappropriately.

Objective: To measure the rate of antiviral and antibiotic prescribing, the appropriateness of antiviral prescribing, and evaluate independent predictors of antiviral and antibiotic prescribing for influenza in primary care.

Design and patients: Retrospective analysis of 958 visits of clinician-diagnosed influenza in 21 primary care clinics in eastern Massachusetts from 1999 to 2007. We considered antiviral prescribing appropriate if patients had symptoms for 2 or fewer days, had fever, and any 2 of headache, sore throat, cough, or myalgias.

Measurements and main results: Clinicians prescribed antivirals in 557 (58%) visits and antibiotics in 104 visits (11%). Of antiviral prescriptions, 38% were not appropriate, most commonly because of symptoms for more than 2 days (24% of antiviral prescriptions). In multivariate modeling, selected independent predictors of antiviral prescribing were symptom duration of 2 or fewer days (odds ratio [OR], 12.4; 95% confidence interval [CI], 8.3 to 18.6), year (OR, 1.4 for each successive influenza season; 95% CI, 1.3 to 1.7), patient age (OR, 1.3 per decade; 95% CI, 1.2 to 1.5), and, compared to having no influenza testing, having a negative influenza test (OR, 5.5; 95% CI, 3.4 to 9.1) or a positive influenza test (OR, 11.4; 95% CI, 6.7 to 19.3). Independent predictors of antibiotic prescribing included otoscopic abnormalities (OR, 3.3; 95% CI, 1.8 to 6.0), abnormal lung examination (OR, 4.0; 95% CI, 2.1 to 6.2), and having a chest x-ray performed (OR, 2.2; 95% CI, 1.3 to 3.8).

Conclusions: Primary care clinicians are much more likely to prescribe antivirals to patients with symptoms for 2 or fewer days, but also commonly prescribe antivirals inappropriately.

Figure 1

Visit flow. * ED is emergency department. ^† MS is multiple sclerosis. ^‡ Most common primary diagnoses were pharyngitis (23%), asthma (6%), fever (4%), bronchitis (3%), otitis media (3%), and non-specific upper respiratory infection (2%). ^§ Most common primary diagnoses were non-specific upper respiratory infection (25%), fever (12%), bronchitis (11%), pharyngitis (10%), and asthma (7%). ** Most common other diagnoses were hypertension (10%), musculoskeletal diagnoses (9%), general medical examination (7%), hyperlipidemia (3%), obesity (1%), and diabetes (1%). ^†† Most common other diagnoses were musculoskeletal diagnoses (41%), hypertension (15%), general medical examination (7%), hyperlipidemia (6%), and diabetes (4%). ^‡‡ After excluding the 1995 emergency department visits, a primary care claims diagnosis of influenza had a positive predictive value of 11% (689 visits with a clinical diagnosis of influenza divided by 6166 primary care visits).

Figure 2

Antiviral and antibiotic prescribing by season * for trend over time, <0.0001 for antivirals and <.02 for antibiotics. Excluding 1999–2000 and 2000–2001, for trend over time, <0.0001 for antivirals and 0.14 for antibiotics. The neuraminidase inhibitors, oseltamivir and zanamivir, as well as 3 of the latest generation rapid influenza tests were introduced prior to the 1999–2000 influenza season.