Swabbing for respiratory viral infections in older patients: a comparison of rayon and nylon flocked swabs

Hernes, S. S.; Quarsten, H.; Hagen, E.; Lyngroth, A. L.; Pripp, A. H.; Bjorvatn, B.; Bakke, P. S.

A virus was recovered from at least one swab in 19 (11%) of the symptomatic patients (Table 3 ), all of whom had reported symptoms of respiratory tract infection. No patients tested positive for more than one virus and no virus was found when reswabbing previously positive patients after four weeks. One patient tested positive for Bordetella pertussis and none for Chlamydophila pneumonia and Mycoplasma pneumonia. As bacterial infections were not the focus of the current study, these results were excluded from the following analysis. In general, nasopharyngeal swabs were positive at a lower CT value compared to oropharyngeal swabs (mean difference CT 4.25, 95% CI 2.43-6.07, p < 0.001), regardless of the sample type (Fig. 1) . The calculated viral load was 19 times higher (95% CI 5.4-67.2) than in the oropharynx. Influenza A virus-positive samples showed a lower CT value in the nasopharynx than in the oropharynx, with a mean difference in CT value of 8.16 (95% CI 6.98-10.35, p < 0.001), which represents a calculated 286 times higher (95% CI 126-1,305) viral load in the nasopharynx.