Saliva testing after COVID-19 exposure might yield good results
Using saliva for SARS-CoV-2 testing is more pleasant and convenient than nasopharyngeal (NP) swab testing, and some reports document similar sensitivity (NEJM JW Gen Med Oct 15 2020 and N Engl J Med 2020; 383:1283; Ann Intern Med 2021; 174:131). For a longitudinal portrait of saliva testing's performance, investigators paired weekly saliva and NP samples from 404 household contacts of known COVID-19 cases, 256 (63%) of whom became infected themselves.
Compared with NP testing, saliva testing's overall sensitivity ranged from a high of 71% during the first week of infection to (20% at 4 or more weeks. During the first 2 weeks of infection, saliva tests were significantly more likely to be positive in the 163 infected contacts with mild or severe symptoms than in the 93 who remained asymptomatic; this difference was most pronounced during the first week of infection (sensitivity, 88% vs. 58%). Correspondingly, saliva testing also performed best in patients who had high viral loads on NP testing.