Oseltamivir overuse at a Chicago hospital during the 2009 influenza pandemic and the poor predictive value of influenza-like illness criteria

We report on the overuse of oseltamivir at Rush University Medical Center, Chicago during the 2009 H1N1 influenza pandemic. Of 210 patients with suspected influenza who underwent respiratory virus reverse transcription polymerase chain reaction (RT-PCR) testing, 113 (54%) received empiric oseltamivir therapy. However, only 50 treated patients (44%) had laboratory confirmed 2009 H1N1. Factors associated with oseltamivir use included a younger median age (including age < 5 y), subjective fever, cough, rhinorrhea, myalgias, higher median temperature, and fulfilment of the US Centers For Disease Control and Prevention (CDC) influenza-like illness (ILI) criteria. However, on multivariate analysis, only subjective fever (p = 0.006, odds ratio (OR) 3.1, 95% confidence interval (CI) 1.4-6.7) and fulfilment of CDC ILI criteria (p = 0.001, OR 3.6, 95% CI 1.7-7.5) were significantly associated with the receipt of oseltamivir. The CDC ILI criteria had a poor positive predictive value of 43% (95% CI 33.3-53.3) for 2009 H1N1. While the ILI criteria are a useful epidemiologic tool, it is too imprecise for direct patient care.