Study population and setting
This study included 533 patients presenting with upper respiratory tract infection symptoms, age 15 months to 94 years, who were seeking care at at five urgent care facilities in the Puget Sound metropolitan area between March 16 to March 21, 2020. The sensitivity of self-collected tongue, nasal and mid-turbinate (MT) swabs were compared to a nasopharyngeal (NP) swab collected by a health care worker (HCW).
Summary of Main Findings
The sensitivity of self-collected nasal and MT samples was greater than 90% (94.0% and 96.2%, respectively) compared to HCW-collected NP samples. Patient-collected tongue sample sensitivity was 89.9% compared to NP sample. Pearson correlation coefficients of PCR Ct values, indicative of how many cycles it took to amplify a sample before the RNA signal crossed the threshold indicating a positive result (a quantitative measure of viral RNA), between positive NP and positive tongue, nasal and MT results were 0.48, 0.78 and 0.86, respectively.
This study included a large sample size of >500 individuals. They were able to compare three different sites of self-collection to a HCW-collected reference of NP swabs.
Limitations of this study include that only one sample per health care worker was compared to 3 samples per patient. Comparisons between identical self-swabs and health care worker swabs would be beneficial to directly compare sensitivities. All participants had symptoms of an upper respiratory tract infection and were seeking care at urgent care centers, therefore these results may not be reflective of sensitivities in asymptomatic or mildly symptomatic cases. A more detailed analysis of the sensitivities of each sample type by time since symptom onset would be helpful, since others have shown that sensitivity of NP tests depends on time since symptom onset.
Patient collected self-samples are equally sensitive for COVID-19 testing compared to samples collected from health care workers