Background: Unsupervised, self-collected nasal swabs (SCNS) are a convenient alternative to collection by health-care workers for influenza-like illness (ILI) surveillance. We compared viral respiratory pathogen detection in paired SCNS versus research coordinator-collected nasal swabs (CCNS). Methods: Adult Military Health System beneficiaries were enrolled in a prospective influenza vaccine effectiveness trial. Following vaccination, participants were contacted weekly to ascertain ILI symptoms. In the event of an ILI, participants completed a symptom diary, a SCNS, and were offered a visit for CCNS. We evaluated respiratory pathogen detection by PCR, concordance between paired swabs (Cohen’s Kappa statistic), and the impact of the timing (days post symptom onset [DPSO]) of collection on detection. Results: 3,357 ILIs were reported during the study period and paired (SCNS and CCNS) swabs were obtained during 1,048 ILIs. Among the paired swabs, SCNS were generally collected earlier than CCNS (median DPSO: 3.0 versus CCNS: 7.0; p < 0.001) and a higher proportion reported moderate or severe symptoms at the time of SCNS collection (43.9% versus 33.3%; p < 0.001). Among 988 swab pairs collected 0-7 days apart, viral pathogen detection was higher in SCNS (39%) versus CCNS (31%) (p<0.001; K=0.59). Paired swabs collected within 7 DPSO (K: 0.63 versus 0.42) were associated with a higher concordance. Conclusions: SCNS are a valid and feasible alternative to CCNS for respiratory virus surveillance and research and may offer higher sensitivity due to an average earlier collection time. Detection of viral pathogens is increased by obtaining swabs within 7 days of symptom onset.
