Clinical performance of three rapid diagnostic tests for influenza virus in nasopharyngeal specimens to detect novel swine-origin influenza viruses.

BACKGROUND: Influenza is an important public health problem. The aim of this study was to evaluate and compare the sensitivity and specificity of three rapid diagnostic tests (SEKISUI, QuickVue Influenza A + B, and SD BIOLINE) for novel swine-origin influenza viruses (S-OIV) and seasonal influenza.
MATERIALS AND METHODS: A total of 210 nasopharyngeal swabs from unique clinical specimens were previously tested by real-time reverse transcription polymerase chain reaction (RT-PCR) assay and tested again in this study. RESULTS AND DISCUSSION: Of these, 164 (78%) were influenza A-positive and 46 (22%) were influenza A-negative by RT-PCR. From 115 positive swabs, 80 (69.6%), 66 (57.4%), and 46 (40.0%) showed S-OIV by SEKISUI, QuickVue Influenza A + B, and SD BIOLINE, respectively. Specific positive and negative predictive values of these three commercial rapid tests were all 100%. Therefore, positive rapid influenza virus diagnosis does not require an RT-PCR confirmatory test. Conversely, only negative rapid influenza virus diagnosis should be evaluated. The SEKISUI test would be a useful diagnostic tool for screening clinical samples for influenza. Concerning the various specimen types, among 25 patients with RT-PCR-proven S-OIV infection, influenza was identified in sputum (21/25; 84.0%) and nasopharyngeal swab (15/25; 60.0%) specimens, but in only 36.0% (9/25) of throat swab specimens. Sputum and nasopharyngeal swab specimens were the most predictive of influenza virus infection, while throat swab specimens were the least predictive of influenza virus infection.