Comparison of a new neuraminidase detection assay with an enzyme immunoassay, immunofluorescence, and culture for rapid detection of influenza A and B viruses in nasal wash specimens

The performance of a new, rapid, easy-to-perform assay based on neuraminida se enzyme activity for detection of influenza virus types A and B was compa red to detection by culture, indirect immunofluorescence, and enzyme immuno assay in 479 nasal wash specimens from children with respiratory infections , Compared to isolation of influenza virus by culture, the neuraminidase as say had a sensitivity of 70.1.%, specificity of 92.4%, positive predictive value of 76.3%, and negative predictive value of 89.9%. There was a higher sensitivity for the detection of influenza A virus (76.4%) than for influen za B virus (40.9%). Indirect immunofluorescence showed a sensitivity of 59. 8% and specificity of 97% compared to culture isolation for detection of in fluenza A and B viruses. Enzyme immunoassay showed a sensitivity of 89.7% a nd specificity of 98.1% for the detection of influenza A alone. The quality of the nasal wash specimen had a significant effect on the detection of in fluenza virus by all of the assays. A strong response of the neuraminidase assay was more likely to represent a culture-confirmed influenza infection. This new rapid neuraminidase assay was useful for the detection of influen za A and B viruses in nasal wash specimens.