Sensitivity of diagnostic tests for influenza varies with the circulating strains

Effective strategies to combat the spread of influenza viruses rely on accurate diagnosis of the infection, which is greatly affected by the sensitivity of the assays used.

To determine if the sensitivity of assays used to detect influenza varies with the viral strains.

This prospective study used 142 respiratory specimens submitted to the clinical virology laboratory during the 2003/2004 influenza season, when the H3N2 Fujian strain was first detected in our community, to assess sensitivities of rapid immunoassay (RIA), shell-vial (SV), hemadsorption (HA)-, and fluorescent antibody (FA)-based conventional tissue culture (TC). Results were compared with similar evaluations performed in 2002/2003 or earlier seasons.

Sensitivities of RIA, SV, HA-TC, and FA-TC were 44, 70, 82, and 100%, respectively for influenza virus circulating in 2003/2004. The comparison with results obtained in previous influenza seasons showed a significantly decreased sensitivity of HA-TC (p=0.02) and lower sensitivity of RIA but without reaching statistical significance (44% versus 72%, p=0.2).

This report underscores the importance of determining the accuracy and sensitivity of diagnostic tests against emerging influenza variant strains.