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 rate was significantly 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.