Comparison of a commercial qualitative real-time RT-PCR kit with direct immunofluorescence assay (DFA) and cell culture for detection of influenza A and B in children

BackgroundInstitutional pandemic planning prompted a study of the molecular detection of influenza virus from respiratory specimens in children, compared to conventional diagnostics.ObjectiveTo evaluate the performance of a commercial qualitative real-time RT-PCR kit (rRT-PCR), the artus™ Influenza LC RT-PCR (Qiagen).Study design (methods)Specimens were pre-selected to include a high percentage of positives by direct immunofluorescence assay (DFA) or culture. The sensitivity and specificity of the kit for detection of influenza A and B in children were determined against the gold standard, DFA and culture. Specimens yielding discordant results between artus™ and the gold standard were tested against a reference rRT-PCR assay (Centers for Disease Control) to create an “expanded gold standard”.ResultsWhen compared to DFA or cell culture, the sensitivity of the rRT-PCR artus™ kit was 96.2% and the specificity was 94%. It detected influenza RNA in 6.0% of clinical samples negative by DFA or culture. Using the expanded gold standard, the revised sensitivity was 98.7% (98.6% for influenza A and 97.6% for influenza B) and the specificity was 100%.ConclusionThe artus™ Influenza LC RT-PCR kit is an effective alternative to virus isolation and DFA for the detection of influenza A and B in pediatric clinical specimens.