Performance of self-collected anterior nasal swabs and saliva specimens for detection of SARS-COV-2 during symptomatic and asymptomatic periods

Grijalva, Carlos G; Rolfes, Melissa; Zhu, Yuwei; Chappell, James; Halasa, Natasha; Kim, Ahra; Reed, Carrie; Fry, Alicia; Talbot, H Keipp

BACKGROUND: Anterior nasal swabs (ANS) are established specimen collection methods for SARS-CoV-2 infection detection. While saliva (SA) specimens provide an alternative, few studies have comprehensively characterized the performance of SA specimens in longitudinal studies. METHODS: We compared SARS-CoV-2 detections between paired self-collected ANS and SA specimens from a household transmission study. Participants recorded symptoms and paired ANS and SA specimens daily for 14 days. Specimens were tested using RT-PCR. We calculated the proportion of detections identified by each specimen type among the detections from both types combined. We computed percent agreement and Kappa statistics to assess concordance in detections. We also computed estimates stratified by presence of symptoms, and examined the influence of traditional and inactivating transport media on the performance of ANS. RESULTS: We examined 2535 self-collected paired specimens from 216 participants. Among 1,238(49%) paired specimens with detections by either specimen type, ANS identified 77.1%[954](95%CI: 74.6–79.3%) and SA 81.9%[1014](79.7–84.0%), with a difference of 4.9%(1.4–8.5%). Overall agreement was 80.0% and Kappa was 0.6(0.5-0.6). Nevertheless, the difference in the proportion of detections identified by ANS and SA using traditional and inactivating transport media was 32.5%(26.8–38.0) and −9.5%(−13.7– -5.2), respectively. Among participants who remained asymptomatic, the difference in detections between SA and ANS was 51.2%(31.8–66.0) and 26.1%(0–48.5) using traditional and inactivating media, respectively. CONCLUSION: Self-collected saliva specimens provide a non-invasive alternative to nasal swabs, especially to those collected in traditional transport media, for longitudinal field studies that aim to detect both symptomatic and asymptomatic SARS-CoV-2 infections.