Abstract
Self-sampling for SARS-CoV-2 would significantly raise testing capacity and reduce healthcare worker (HCW) exposure to infectious droplets personal, and protective equipment (PPE) use. We conducted a diagnostic accuracy study where subjects with a confirmed diagnosis of COVID-19 (n = 401) and healthy volunteers (n = 100) were asked to self-swab from their oropharynx and mid-turbinate (OPMT), and self-collect saliva. The results of these samples were compared to an OPMT performed by a HCW in the same patient at the same session. In subjects confirmed to have COVID-19, the sensitivities of the HCW-swab, self-swab, saliva, and combined self-swab plus saliva samples were 82.8%, 75.1%, 74.3% and 86.5% respectively. All samples obtained from healthy volunteers were tested negative. Compared to HCW-swab, the sensitivities of a self-swab sample and saliva sample were inferior by 8.7% (95%CI: 2.4% to 15.0%, p = 0.006) and 9.5% (95%CI: 3.1% to 15.8%, p = 0.003) respectively. The combined detection rate of self-swab and saliva had a sensitivity of 2.7% (95%CI: -2.6% to 8.0%, p = 0.321). The sensitivity of both the self-collection methods are higher when the Ct value of the HCW swab is less than 30. The specificity of both the self-swab and saliva testing was 100% (95% CI 96.4% to 100%). Our study provides evidence that sensitivities of self-collected OPMT swab and saliva samples were inferior to a HCW swab, but they could still be useful testing tools in the appropriate clinical settings.
Highlights
The current “gold standard” for testing for SARS-CoV-2 requires health care workers to collect a nasopharyngeal (NP) sample from a patient
Compared to healthcare worker (HCW)-swab, the sensitivities of a self-swab sample and saliva sample were inferior by 8.7% (95%confidence interval (CI): 2.4% to 15.0%, p = 0.006) and 9.5% (95%CI: 3.1% to 15.8%, p = 0.003) respectively
The combined detection rate of self-swab and saliva had a sensitivity of 2.7% (95%CI: -2.6% to 8.0%, p = 0.321)
Summary
The current “gold standard” for testing for SARS-CoV-2 requires health care workers to collect a nasopharyngeal (NP) sample from a patient. A prior study has shown that a combination of oropharyngeal and anterior nares swabs is equivalent in sensitivity to an NP swab in 190 ambulatory symptomatic patients [1]. In another study on 236 ambulatory subjects, the performance of self-collected nasal and throat swabs is at least equivalent to that of health worker collected swabs for the detection of SARS-CoV-2 and other respiratory viruses [2]. In a recent study by Yale University on 29 subjects [3], it was suggested that a large volume sample of saliva collected from COVID-19 inpatients can be more sensitive than NP swabs for SARS-CoV-2 detection, and saliva samples had significantly higher COVID-19 viral titres than NP swabs (p = 0.001).
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