Evaluation of Self-Collected Midturbinate Nasal Swabs and Saliva for Detection of SARS-CoV-2 RNA

Rapid and accurate diagnostic testing is essential to bring the ongoing COVID-19 pandemic to an end. As the demand for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing continues to increase amid supply shortages, many laboratories have investigated the use of sources other than nasopharyngeal (NP) swabs. Saliva and midturbinate (MT) nasal swabs are attractive alternatives, as they allow for self-collection and are well accepted by patients. Saliva also requires limited consumables. We compared the performance of health care provider-collected NP swabs, patient-collected MT swabs, and patient-collected saliva specimens for SARS-CoV-2 detection using a laboratory-developed PCR assay that had received Emergency Use Authorization by the FDA. Of 281 total evaluable samples, 33 (11.7%) NP swabs, 33 (11.7%) MT swabs, and 32 (11.4%) saliva specimens were positive for SARS-CoV-2 following resolution of discordant results. Compared to NP swabs, saliva exhibited a sensitivity of 90.9% (30/33) and specificity of 99.2% (246/248), while patient-collected MT swabs exhibited a sensitivity of 93.9% (31/33) and specificity of 99.2% (246/248). When comparing to the consensus standard, the sensitivity was found to be 100% (31/31) for both NP and MT swabs and 96.8% (30/31) for saliva specimens, while specificity was the same in both NP swabs and saliva specimens (98.8% [247/250]) and 99.2% (248/250) for MT swabs. Pretreatment of saliva with proteinase K and heating for 15 min prior to extraction reduced the invalid rate from 26.7% (52/195) to 0% (0/195). These data show that midturbinate nasal swabs and saliva are suitable sources for self-collection in individuals who require routine monitoring for SARS-CoV-2 infection.