Current best evidence for clinical care (more info)
The clinical utility of antigen test using anterior nasal samples has not been well evaluated. We conducted a prospective study in a drive-through testing site located at a PCR center to evaluate the diagnostic performance of the antigen test QuickNavi-COVID19 Ag using anterior nasal samples and to compare the degrees of coughs or sneezes induction and the severity of pain between anterior nasal collection and nasopharyngeal collection. The study included a total of 862 participants, of which 91.6% were symptomatic. The median duration from symptom onset to sample collection was 2.0 days. Fifty-one participants tested positive for severe acute respiratory syndrome coronavirus 2 on reverse transcription PCR (RT-PCR) with nasopharyngeal samples, and all of them were symptomatic. In comparison to the findings of RT-PCR, the antigen test using anterior nasal samples showed 72.5% sensitivity (95% confidence interval [CI] 58.3-84.1%) and 100% specificity (95% CI 99.3-100%). Anterior nasal collection was associated with a significantly lower degree of coughs or sneezes induction and the severity of pain in comparison to nasopharyngeal collection (p < 0.001). The antigen test using anterior nasal samples showed moderate sensitivity in symptomatic patients who were at the early stages of the disease course but was less painful and induced fewer coughs or sneezes.
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This article gives some guidance in the use of anterior naso swabs.
With all the publicity about opening back up and the requirements for testing, it's nice to have some information about the reliability of those tests in order to better inform social policy.
It's important for us to understand the sensitivity of antigen tests as we move into the post-pandemic phase for COVID-19. This study uses an excellent gold standard of PCR though the tested population is >90% symptomatic; therefore, a diagnostic rather than screening trial of this more mobile and presumably less costly assay.
Compared with other studies, the sensitivity does not appear to be lower than ag tests sampled from the pharynx (it should have been compared with this in the same study). I don't think cough or sneeze is an important end-point.