Evaluation of 3 rapid influenza diagnostic tests during the 2012-2013 epidemic: influences of subtype and viral load

This article evaluates the performance of 3 rapid influenza diagnostic tests (RIDTs), in correlation with the influenza subtypes and the viral load. A total of 236 samples were prospectively analyzed with BinaxNOW Influenza A/B, Directigen EZ Flu A and B, and bioNexia Influenza A+B. The results were compared to cell cultures and real-time polymerase chain reaction. Positive samples were further subtyped. Thirty-seven samples were positive for influenza A, and 57, for influenza B. For A(H1N1), the sensitivities were 71.42% for BinaxNOW, 78.57% for Directigen, and 67.85% for bioNexia. Eight samples were positive for A(H3N2), and only the bioNexia test had 1 false-negative result. Lowest sensitivities were observed for influenza B/Yamagata, (56.86% for BinaxNOW and Directigen and 39.21% for bioNexia). The 3 evaluated RIDTs were more efficient at detecting influenza A(H3N2) than for A(H1N1) and B/Yamagata. Highest viral loads in the samples were associated with better rate of detection.