Rapid assays for the diagnosis of influenza A and B viruses in patients evaluated at a large tertiary care children's hospital during two consecutive winter seasons

Abstract Background The rapid and accurate diagnosis of influenza facilitates antiviral therapy, judicious antibiotic usage, and cohorting patients to decrease nosocomial infection. Objective To determine the utility of rapid influenza tests in a children's hospital. Study design Two in vitro rapid immunochromatographic assays that detect and distinguish influenza A and B viruses were compared to the reference standard of viral culture. Results In 9186 patients tested, overall sensitivity of the rapid assays for influenza A was 64.4% and specificity was 98.3%. Sensitivity and specificity were 28% and 99.9%, respectively, for influenza B. Overall sensitivity and specificity for Remel Xpect (2004/2005) were 47.7% and 98.7% for influenza A, and 20.3% and 99.8% for influenza B, respectively. Overall sensitivity and specificity of Binax NOW Flu A&B (2005/2006) were 78.3% and 98% for influenza A, and 35.9% and 99.9% for influenza B, respectively. The results for influenza B with both assays were significantly lower than previously reported and lower than stated in the manufacturer's package insert. Conclusions In a contemporary clinical setting, rapid assays for influenza displayed significantly lower sensitivities, especially for influenza B, than prior reports. Differences in pre- and post-licensure performance demonstrate the importance of continuous evaluation of rapid diagnostic tests for influenza.