Clinical evaluation of rapid point-of-care testing for detection of novel influenza A (H1N1) virus in a population-based study in Spain

Limited information exists on the performance of antigen-based rapid influenza diagnostic tests (RIDT) in diagnosing the novel influenza A pandemic (H1N1) 2009 virus. Large studies evaluating these tests in consecutive patients with a broad clinical spectrum of influenza-like illnesses are needed. We assessed the ClearView® Exact Influenza A & B test (Inverness Medical, Cologne, Germany) in comparison with real-time (r)RT-PCR for detection of the novel influenza A (H1N1) in a population-based prospective study of 1016 adults and children with suspected influenza in Spain. Three hundred and one (29.6%) patients had a positive sample with the rRT-PCR assay for influenza A and B viruses, with 297 (29.2%) confirmed cases of the novel influenza A pandemic (H1N1) 2009 virus. Fifty (16.8%) patients with confirmed A (H1N1) 2009 virus were admitted to hospital, with six of them to the intensive care unit. In comparison with rRT-PCR, the ClearView® Exact Influenza A & B test had a sensitivity of 19% (95% CI 14-23), a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 75% (95% CI 72-78). The sensitivity of the test remained low across all demographic and clinical strata. Although a positive RIDT performed well in predicting PCR-confirmed infection with pandemic H1N1 virus, the sensitivity was very low and a negative test result was a poor predictor of the absence of infection.