A Comparison of Self-Collected Nasal Flocked Swabs with Staff-collected Nasopharyngeal or Nasal swabs for Respiratory Tract Sampling in Volunteers

Objectives: Nasal swabs (NS) for diagnosis of respiratory viruses are less invasive than nasopharyngeal swabs (NPS), and may enable self-collection. Previously, we studied 2 NS prototypes, and found them equivalent to NPS in sampling epithelial cells, but self-collection was inferior to staff collection. In this study we modified one of the nasal flocked swab (NFS) to optimize sampling and comfort, and to validate that 2 sequential NS will optimize respiratory cell sampling. Our objective was to examine if the new Copan NFS is equivalent to NPS in sampling the respiratory tract, and if self-sampling is equivalent to staff sampling.

Methods: 55 volunteers had 2 self-administered NFS, followed by 2 staff-administered NS using NFS or rayon swabs in random order. Pictorial instructions were provided. Discomfort, ease of administration, and preferences were assessed. The 2nd self-collected swab was compared with the staff-collected swab. 20 subjects had 2 NPS with pernasal FS or rayon swab. Swabs were placed in a one mL tube of UTM®; 500 ul was used for nucleic acid extraction and 500 ul to prepare cell smears. Epithelial cells were counted under an UV microscope; Averaging 4 fields or 10 fields when less than 10 cells per high-powered field (hpf) were present. DNA was quantitated using a beta-Actin real time PCR.

Results: In the 55 volunteers, the 2nd self-collected NS was superior to the initial swab, with a mean (SD) of 117 (65) vs. 67 (43) cells/hpf. The 2nd self-collected NS was superior to staff-collected rayon NS {38 (25) cells/hpf}, and comparable to staff-collected flocked NS {132 (56) cells/hpf}. In the 20 subjects with NPS, the mean NPS (SD) cell yields were 145 (43) and 55 (30) for the flocked and rayon, respectively; and 136 (53) and 32 (22) for flocked or rayon staff-administered NS. A high correlation was found between the cell count and log DNA copies/ml (R=0.9, P<0.001). No difference was found between self and staff administered flocked NS or NPS. Flocked NS performed better than rayon with significant higher mean log DNA count. Mild discomfort or ease in self-swabbing was reported. Self-swabbing was preferred to staff collection.

Conclusions: The new Copan nasal flocked swab design is superior to rayon NPS or NS, and equivalent to flocked NPS, for sampling respiratory epithelial cells or DNA. Self nasal sampling is feasible and easy to perform, and equivalent to staff sampling. 2 sequential swabs are required for optimal cell yield.

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