Diagnosis of influenza virus.

The laboratory diagnosis of influenza uses a wide range of techniques including rapid immunoassays, immunofluorescence techniques, virus culture methods, and increasingly sophisticated molecular assays. The potential utility of each of these methods has changed over the years, most dramatically perhaps with the emergence of the pandemic H1N1 2009 influenza virus. While rapid immunoassays had previously been widely used in clinics and emergency departments, their poor detection sensitivity for the 2009 subtype brought their application into question. Concerns were also raised about the detection sensitivities of antibody reagents used in immunofluorescence methods, and the safety of virus culture was initially questioned with regard to the newly emerged subtype. Early molecular detection techniques had been labor intensive, and required separate facilities in order to prevent contamination. Those techniques have largely been supplanted by more modern methods, most notably real-time reverse transcription PCR assays, which are currently the method of choice in many laboratories for the detection and subtyping of influenza viruses. Suspension and low-density array assays are also increasingly used, in an effort to detect larger numbers of viruses in a single assay, and microarrays have proven valuable for outbreak analysis and pathogen discovery. Each laboratory must assess the optimal methods for its situation and the best application of each technique, taking into account numerous factors including its budget, equipment, staff expertise, the patient population that it serves, the needs of its submitting clinicians, and its surveillance and public health responsibilities.