Self-Collected Nasal Flocked Swabs for Respiratory Tract Sampling in Volunteers
Nasal swab (NS) collection for diagnosis of respiratory viruses is less invasive than nasopharyngeal swabs (NPS). Recently, we found that newly designed NS were essentially equivalent to NPS in sampling respiratory epithelial cells. In this study, we assessed the feasibility and quality of self- sampled NS compared with staff-collection.
We enrolled 35 volunteers, each of whom collected two self- administered NS (round and flat) using written and illustrated instructions; followed by another two NS (round and flat) collected by trained staff. The order of NS type was randomized. Discomfort, ease of administration, and preferences were assessed using a Likert scale. Swabs were placed in 1.0 mL Copan Universal Transport Medium, vortexed and centrifuged, and pellets resuspended in 1.0 mL of PBS. 25 microL suspensions were placed in wells on a glass slide, dried, fixed and counterstained with FITC labeled monoclonal antibody. Respiratory epithelial cells were enumerated using a fluorescent microscope at 400x magnification by an experienced microscopist blinded to swab type and administration. An average count from 4 fields was calculated when 10 or more epithelial cells were present per high-powered field (hpf); 10 fields were averaged if there was fewer than 10 cells/hpf.
Among the 35 subjects, the mean (SD) cell yields for round swabs were 81.1 (44.8) and 43.2 (38.1) for researcher- and self-administered NS respectively (P<0.001); cell yields for flat swabs were 76.6 (45.0) and 36.0 (29.9) (P<0.001). While round NS collected more cells than flat NS, the difference was not statistically significant. However, using a widely-accepted definition of an adequate diagnostic smear of greater than 25 epithelial cells/smear, 69 of 70 self-collected and all 70 staff-collected specimens were of adequate quality. Overall, both flat and round NS were well tolerated with 75% of volunteers reporting no or mild discomfort. Self-administration of NS was easy (97%) and a majority of individuals (75%) were either neutral or preferred self-collection.
Self-administered nasal sampling was easy, preferred, but may be inferior to staff-collected swabs for sampling the upper respiratory tract. Studies with clinical correlation are now needed.