Performance characteristics of a rapid immunochromatographic assay for detection of pandemic influenza A (H1N1) virus in children

Abstract

Rapid tests for diagnosis of influenza are valuable assets in the management of influenza in pediatric patients. However, test performance fluctuates with virus subtypes. We assessed the test characteristics of Influenzatop®, a rapid immunochromatographic influenza A and B test, in detecting pandemic 2009 influenza A (H1N1) in children up to 18 years of age, using reverse transcriptase polymerase chain reaction (RT-PCR) as the gold standard. Three hundred and one pediatric outpatients with influenza-like illness were included into the study. Overall sensitivity of Influenzatop® was 64% (95% confidence interval (CI) 56–71%) but increased to 92% (95% CI, 80–97%) when performed between 24 and 48 h after onset of symptoms. Positive Influenzatop® results among RT-PCR-positive patients were associated with higher viral load. No significant variation in test performance could be detected when analyzed by age and high versus low prevalence period. Overall test specificity was 99% (95% CI, 95–100%); positive and negative predictive values were 98% (95% CI, 93–99%) and 70% (95% CI, 63–76%), respectively. Conclusion: Influenzatop® rapid influenza test is a sound tool in the diagnosis of H1N1 in pediatric patients when employed 24–48 h after onset of symptoms.