Influenza diagnosis: From dark isolation into the molecular light

Objectives: To compare the conventional virus isolation method for diagnosi s of influenza infection with reverse-transcription polymerase chain reacti on (RT-PCR) in prospectively collected nose and throat swabs From elderly p atients during the winter influenza season, The use of a denaturing buffer as an alternative to viral transport medium (VTM) for submission of combine d nose and throat swabs to the laboratory for PCR was then investigated in a second study Methods: Virus was cultured in microtitre plates using two different cell l ines and detected using monoclonal antibody staining. A multiples, matrix g ene PCR assay was optimized to increase the sensitivity and specificity of detection of influenza A (H3 and H1) and B nucleic acid. Results: The multiplex assay detected all viruses with equal sensitivity to individual assays, In a large, multicentre field study PCR detected twice as many influenza infections compared with virus isolation, No positive cul ture was missed. PCR has a rapid turn around time (< 36 h) vs, a minimum of 7 days for virus isolation, Greater sensitivity and specificity in the PCR were achieved using a 'hot-start' method. Although the numbers were small, the detection rate using PCR was greater for swabs submitted in denaturing buffer than in VTM. Conclusions: PCR significantly increased the sensitivity and clinical utili ty of influenza A (HS and H1) and B diagnosis, There were a number of advan tages in using denaturing buffer for submission of samples, including high sensitivity, rapidity, ease of use and no requirement for the virus to be v iable on arrival at the laboratory Therefore, PCR is a rapid, sensitive and user-friendly alternative for influenza diagnosis, Virus isolation technol ogy should be limited to referral centres for further epidemiological chara cterization. (C) 1999 The British Infection Society.