Rapid, accurate, and cost-effective methods to identify the cause of respiratory tract infections are needed to maximize clinical benefit. Outpatients with acute respiratory illness were tested for influenza using a singleplex reverse transcriptase polymerase chain reaction (SRT-PCR) method. A multiplex RT-PCR (MRT-PCR) method tested for influenza and 17 other viruses and was compared with SRT-PCR using chi-square tests. Among 935 patients, 335 (36%) tested positive for influenza A and influenza B using SRT-PCR. Using MRT-PCR, 320 (34.2%) tested positive for influenza A and influenza B. This study supports MRT-PCR as a comparable method for detecting influenza among patients seeking outpatient care for acute respiratory illnesses. 1. Background Each year millions of people are afflicted with influenza-associated respiratory tract infections, some of which lead patients to seek outpatient medical attention, referred to as medically attended acute respiratory infection (ARI). Rapid, accurate, and cost-effective methods are needed to maximize clinical benefit of antivirals and reduce inappropriate antibiotic usage. New assay methods using multiplex reverse transcriptase polymerase chain reaction (MRT-PCR) are available that allow for relatively rapid detection of multiple virus types including influenza [1, 2]. 2. Objective During the 2012-2013 influenza season, the Centers for Disease Control and Prevention (CDC)-funded, multicenter US Influenza Vaccine Effectiveness (Flu VE) Network conducted a study designed to determine the effectiveness of the season’s influenza vaccine. That study used singleplex RT-PCR (SRT-PCR) to detect influenza virus. The University of Pittsburgh site of the Flu VE Network also used MRT-PCR. The purpose of this study was to compare the agreement between SRT-PCR and MRT-PCR for influenza virus detection. 3. Study Design The US Flu VE Network evaluated the effectiveness of the season’s influenza vaccine using a test-negative, case-control study design [3, 4], where the proportion vaccinated among those who test positive for influenza was compared with the proportion vaccinated among those who test negative. Participants in the current study were enrollees in the University of Pittsburgh site of the Flu VE study, described previously . Eligibility criteria included patients aged ≥6 months as of 9/1/2012, seeking outpatient medical care for an upper respiratory illness of ≤7 days’ duration with cough, and not taking an influenza antiviral before the visit. This prospective study was approved by the University of Pittsburgh
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