Diagnosis of community-acquired acute respiratory illness: From conventional microbiological methods to molecular detection (multiplex).

Investigations of the etiologic agents of community-acquired acute respiratory illness may lead to better treatment decisions and patient outcomes. In a routine care setting, we assessed the diagnostic performance of a multiplex PCR assay with respect to conventional microbiological methods, in a continuous series of adult cases of community-acquired acute respiratory illness. We enrolled 279 adult patients hospitalised for community-acquired acute respiratory illness at Tours University Hospital during the winter of 2011-2012. Respiratory samples (mostly nasopharyngeal aspirates) were studied prospectively by indirect immunofluorescence assay and multiplex PCR, that enable detection of 8 viruses and 21 respiratory pathogens respectively. In total, 255 of the 279 (91.4%) samples had interpretable results by both methods. At least one respiratory pathogen was detected by multiplex PCR in 171 specimens (65%). Overall, 130 (76%) of the 171 positive samples were positive for only one respiratory pathogen, 37 (22%) samples were positive for two pathogens and four (2%) were positive for three pathogens. With indirect immunofluorescence assay, a respiratory virus was detected in 27 of the 255 (11%) specimens. Indirect immunofluorescence assay detected some of the influenza virus A (15/51, 29%) infections identified by multiplex PCR and some (7/15, 47%) human metapneumovirus and (5/12, 42%) respiratory syncytial virus infections, but it did not detect all the adenovirus infections. Thus, access to multiplex molecular assays improves the diagnostic spectrum and accuracy over conventional methods, increasing the frequency of identification of the respiratory pathogens involved in community-acquired acute respiratory illness.