Utility of the antigen test for coronavirus disease 2019: Factors influencing the prediction of the possibility of disease transmission

Abstract

Rapid antigen testing (RAT) for coronavirus disease 2019 (COVID-19) has lower sensitivity but high accuracy during the early stage when compared to reverse transcription quantitative polymerase chain reaction (RT-qPCR). The aim of this study was to investigate the concordance between RAT and RT-qPCR results, and their prediction of disease transmission. Methods: This single-center retrospective observational study of inpatients with COVID-19 was conducted from March 6 to June 14, 2020. Nasopharyngeal swabs were used to perform RAT and RT-qPCR. The primary endpoint was concordance between RAT and RT-qPCR results. The secondary endpoints were the factors causing disagreement in the results and the estimated transmissibility in RT-qPCR-positive patients with mild symptoms. Results: Overall, 229 samples in viral transport medium (VTM) were obtained from 105 patients. The positive and negative concordance rates for VTM were 41% vs 99% (k = 0.37) and 72% vs 100% (k = 0.50) for samples collected on disease days 2-9. An increased body temperature (odds ratio 0.54) and absence of drugs with potential antiviral effect (odds ratio 0.48) yielded conflicting results. RAT was associated with the ability to end isolation (OR 0.11, 95% confidence interval 0.20-0.61). Conclusions: RAT and RT-qPCR results were highly consistent for samples collected at the appropriate time and could be useful for inferring the possibility of transmissibility.

Time-course evaluation of the quantitative antigen test for severe acute respiratory syndrome coronavirus 2: The potential contribution to alleviating isolation of COVID-19 patients

“…Kohmer et al reported that the antigen-detecting rapid diagnostic test correlated better with cell culture infectivity in vitro than RT-qPCR (61.8%-82.4% vs 51.6%) [7]. Our previous study also implied the utility of qualitative antigen testing in predicting the appropriate duration of quarantine [16]. Qualitative antigen tests generally tend to be less sensitive, and false-negative results in contagious patients have been a challenge.…”

Does the SARS-CoV-2 rapid antigen test result correlate with the viral culture result?

“…Of these, seven of eight RAT-positive samples (88%) and three of ten RAT-negative samples (30%) were positive on viral culture [7]. There were fewer samples that were positive based on viral culture in our study than in the study by Yamamoto et al [1] because a higher proportion of the samples in our study were collected >9 days after symptom onset. Positive viral culture results are known to be associated with the number of days since the disease onset [8].…”

“…RAT might be a useful indicator of infectiousness, which can be helpful to control infection. However, further studies with larger sample size are warranted to confirm this observation.Immunochromatographic rapid antigen tests (RATs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are simple to perform and have a relatively low cost but they have a low sensitivity [1][2][3]. A potential advantage of the low sensitivity of RATs is that they do not remain positive during the long period of low viral excretion after infectiousness has passed [4].…”

“…In a previous study, we determined that the concordance with reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in the early stage of COVID-19 (within 9 days after symptom onset) was 72% for positive and 100% for negative RAT results. Moreover, in samples with >10 3 copies/test (>85 copies/μL), the positive concordance was 85% [1]. We hypothesized the RAT results might be useful for determining whether an individual is still infectious during the convalescent phase when there is no fever and the virus is presumed to be no longer infectious.…”

“…Immunochromatographic rapid antigen tests (RATs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are simple to perform and have a relatively low cost but they have a low sensitivity [1][2][3]. A potential advantage of the low sensitivity of RATs is that they do not remain positive during the long period of low viral excretion after infectiousness has passed [4].…”