Diagnostic performance and characteristics of anterior nasal collection for the SARS-CoV-2 antigen test: a prospective study

Abstract

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.

Figure 1

Comparison of SARS-CoV-2 viral loads between each collection site and swab type. The set of viral loads in the same participant is represented by connected lines. The viral loads were compared by the Wilcoxon signed-rank test, and p values are corrected with Holm correction. NP-type swab nasopharyngeal-type swab, OP-type swab oropharyngeal-type swab, CI confidence interval, IQR interquartile range.

Figure 2

Degrees of coughs or sneezes induced by anterior nasal and nasopharyngeal collection. The degrees of coughing or sneezing following swab insertion was compared between anterior nasal collection and nasopharyngeal collection in the same participant (n = 784). The degrees were rated on a four-point scale. The McNemar–Bowker test was used for the comparison.

Figure 3

The pain score in anterior nasal collection and nasopharyngeal collection. The severity of pain at swab insertion was assessed on a five-point scale, from 1 to 5 (Pain score). The pain score for each collection method was obtained from the same participant (n = 90). The comparison of the pain scores with the two collection procedures was performed with the Wilcoxon signed-rank test.