Nasal washes vs nasopharyngeal swabs for the detection of respiratory pathogens

Abstract

Background: Respiratory virus testing is frustrated by low sensitivity, estimated as low as 70%. One cause for this may be the method of sampling used. The question of which method of sampling yields pathogens with optimal sensitivity between nasopharyngeal swabs, nasal washes and aspirates was answered systematically, using new methodology for rapid reviews. Methods: Cochrane interim guidance for conducting rapid reviews and the PRISMA protocol for combination of metanalysis and narrative synthesis. The study used the QUADAS-2 tool for risk of bias Revman and Rayyan QCRI software, and was registered with PROSPERO. Sensitivities were compared head-to-head against a consensus standard of positivity by either method as the gold standard. Insufficient, cross sectional and anatomical site-pooling methodologies were excluded. Results: Of 13 eligible studies, 9 included infants, 6 included children under the age of 16 and 4 included adults. 8 had ‘high’ risk of bias, and 5 had ‘high’ applicability concerns. There were no statistical differences in pooled sensitivities between collection methods for 8 different viruses, and neither with use of PCR, immunofluorescence nor culture. In one study, Influenza H1N1 favoured nasopharyngeal swabs, with aspirates having 93.3% of the sensitivity of swabs (p > 0.001). Conclusions: The chain of sampling, from anatomical site to laboratory results, features different potential foci along which sensitivity may be lost. A moderate body of evidence exists that use of a different sampling method between swabs and aspirates will not yield more respiratory pathogens. A new rapid reviews protocol helped answer this question in a 3 month period.