Re-evaluation of clinical utility of throat swab specimens for a rapid influenza diagnostic test

Abstract

Throat swab specimens collected from 439 patients with influenza-like symptoms visiting a clinic in the 2004-2005 influenza season were subjected to cell culture virus isolation and viral antigen detection using a rapid diagnostic kit, QuickVue Rapid SP influ (Quidel Corporation, San Diego, CA, U.S.A.). The sensitivity and specificity of diagnostic kit results were analyzed based on cell culture results, considered the diagnostic standard. Kit sensitivity was 87.8% (72/82) and specificity 90.2% (322/357) for type A influenza, and 80.4% (176/219) and 95.0% (209/220) for type B influenza, roughly comparable to results reported so far for nasopharyngeal swabs and/or nasal aspirates. Sensitivity and specificity calculated separately dividing patient age but no significant difference was seen. The antigen-detection kit thus appears clinically useful in diagnosing influenza, provided that is collected and processed properly.