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.

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.