Evaluation of diagnostic and therapeutic approaches for suspected influenza A(H1N1)pdm09 infection, 2009-2010.

To assess adherence to real-time changes in guidelines for influenza diagnosis and use of oseltamivir during the 2009 influenza A(H1N1) pandemic, we reviewed medical records of patients with confirmed or suspected influenza-like illness (ILI) and those with no viral testing in a large Los Angeles (California, USA) hospital. Of 882 tested patients, 178 had results positive for influenza; 136 of the remaining patients received oseltamivir despite negative or no results. Oseltamivir use was consistent with national recommendations in >90%. Of inpatients, children were less likely than adults to have ILI at testing and to receive oseltamivir if ILI was found. Of outpatients, children were more likely to have positive test results; 20% tested did not have ILI or other influenza signs and symptoms. Twenty-five of 96 test-positive patients and 13 of 19 with lower respiratory tract disease were, inappropriately, not treated. Variations between practice and national recommendations could inform clinical education in future influenza seasons.