Evaluation of the ESPLINE® Influenza A & B-N assay for the detection of influenza A and B in nasopharyngeal aspirates.

Several direct antigen tests for the detection of influenza often lack sensitivity compared to immunofluorescence (IF) on the specimens and viral culture (VC). We evaluated the performance of a rapid test, the ESPLINE® Influenza A & B-N assay. A total of 302 respiratory specimens were collected at the University Hospital of Antwerp. A first group of 60 samples taken during the H1N1 outbreak (2009-2010) and a second group of 242 samples stored during the seasonal influenza epidemics (2000-2009) were analyzed with the ESPLINE® test. A subset of samples were also evaluated with the BinaxNOW Influenza and the Clearview Exact Influenza. The results were compared to IF on the specimens, VC with IF, and the combination of both, which was considered as the gold standard. The ESPLINE® test's overall sensitivity and specificity were 91% and 97%, during the H1N1 season 80% and 93%, and for the detection of seasonal influenza 93% and 97%, respectively. In comparison to the BinaxNOW Influenza and the Clearview Exact Influenza, all tests demonstrated a similar specificity of 92.0-100% but a significantly different sensitivity of 44.4-86.0%, with the ESPLINE® test being significantly more sensitive. Due to its very good performance and simplicity, the ESPLINE® test facilitates urgent testing. The test seems less sensitive to detect H1N1 compared to seasonal influenza, although the difference is borderline not significant (p = 0.067).