Respiratory tract illness surveillance in patients at a community clinic during the 2010 influenza season

Viruses cause the majority of respiratory infections. A rapid laboratory method to accurately diagnose etiology of respiratory illness can inform physicians and guide treatment decisions. The objective of this cross-sectional, laboratory based surveillance study is to assess the sensitivity and specificity of influenza virus rapid antigen assay Quidel A+B (Quidel, San Diego, CA) and two multiplex respiratory pathogen assays [Idaho Technology FilmArray® Respiratory Panel (Idaho Technology, Inc., Salt Lake City, UT) and Qiagen ResPlex™ II (Qiagen, Germantown, MD)] compared with influenza virus polymerase chain reaction (PCR) assays. Patients seeking treatment for influenza-like-illness (ILI) in the outpatient setting were identified between October 17, 2010 and May 31, 2011. A total of 1,481 ILI patients were seen. Nasal specimens were collected and tested on all assays for 253 of these patients. Sensitivity and specificity of each influenza and multiplex respiratory assay was calculated relative to a gold standard PCR assay. The self-reported symptom profiles of each organism identified in the respiratory pathogen panels were compared. The median patient age was 12 years (range: 0-89 years); 176 (70%) had one or more viruses detected in the nasal swab specimen. Sensitivity for influenza A was 92% (95% CI: 88-99%) for FilmArray® RP, 85% (95% CI: 81- 96%) for ResPlex™ II, and 38% (95% CI: 48-71%) for Rapid, with specificities of 99.5-100%. Sensitivity for influenza B was 85% (95% CI: 86-99%), 70% (95% CI: 66-90%) for ResPlex™ II, and 6% (95% CI: 0-23%) for Rapid, with specificities of 99.5-100%. A similar pattern was seen for noninfluenza viruses, with the FilmArray® RP assay being more sensitive and specific than the ResPlex™ II. The use of multiplex viral assays is becoming more common in point-of-care settings. In this study, the Idaho Technology FilmArray® Respiratory Panel was more sensitive and specific than the Qiagen ResPlex™ II assay for influenza A and B viruses, as well as other common respiratory viruses.