Identification of respiratory viruses in adults: nasopharyngeal versus oropharyngeal sampling

The optimal method for identifying respiratory viruses in adults has not been established. The objective of the study was to compare the sensitivities of three sampling methods for this purpose. One thousand participants (mean age, 63.1 +/- 17.8 years) were included. Of these, 550 were patients hospitalized for acute febrile lower respiratory tract infections and 450 were controls. Oropharyngeal swabs (OPS), nasopharyngeal swabs (NPS), and nasopharyngeal washings (NPW) were obtained from each participant and were tested for 12 respiratory viruses by a multiplex hydrolysis probes-based quantitative real-time reverse transcription-PCR. Patients were defined as positive for a specific virus if the virus was identified by at least one sampling method. In all, 251 viruses were identified in 244 participants. For the detection of any virus, the sensitivity rates for OPS, NPS, and NPW were 54.2%, 73.3%, and 84.9%, respectively (for OPS versus NPS and NPW, P < 0.00001; for NPS versus NPW, P < 0.003). Maximal sensitivity was obtained only with sampling by all three methods. The same gradation of sensitivity for the three sampling methods was found when influenza viruses, coronaviruses, and rhinoviruses were analyzed separately. The three sampling methods yielded equal sensitivity rates for respiratory syncytial virus. We conclude that nasopharyngeal sampling has a higher rate of sensitivity than oropharyngeal sampling and that the use of NPW has a higher rate of sensitivity than the use of NPS with a rigid cotton swab for the identification of respiratory viruses in adults. Sampling by all three methods is required for the maximal detection of respiratory viruses.