Prospective evaluation of a novel multiplex real-time PCR assay for detection of fifteen respiratory pathogens-Duration of symptoms significantly affects detection rate

Background: Nucleic acid amplification techniques have improved the diagnostic possibilities in respiratory tract infections, although their clinical applicability is not yet fully defined. We have evaluated a multiplex real-time PCR method for the detection of 13 respiratory viruses and 2 bacteria (Mycoplasma and Chlamydophila) in a clinical setting. Objectives: The aim of the present study was to evaluate the diagnostic performance and clinical use of a novel multiplex PCR method in adults with community-acquired respiratory viral infection, and the impact of duration of symptoms on detection rates. Study design: Nasopharyngeal swab samples were prospectively collected from 209 adult outpatients with respiratory infections and 100 asymptomatic controls. Results: An infectious agent was identified in 43% of samples from patients and 2% of asymptomatic controls. The detection ratewassignificantly higher in samples from patients with a duration of symptoms of 6 days or less (51%) than in samples from patients with a duration of symptoms of 7 days or more (30%, p < 0.01). For human corona viruses, and influenza virus A and B there was a correlation between the amount of virus in each patient sample as measured Ct values and duration of symptoms. Conclusions: Duration of symptoms significantly affects the detection rate of respiratory pathogens by multiplex real-time PCR in nasopharyngeal swab samples from adult patients with respiratory infections. Our finding should be taken into account when using these tests in clinical practise. (C) 2009 Elsevier B.V. All rights reserved.