Potential usage of anterior nasal sampling in clinical practice with three rapid antigen tests for SARS-CoV-2

Introduction Anterior nasal sampling (AN) might be more convenient for patients than NP sampling to diagnose coronavirus disease. This study investigated the feasibility of rapid antigen tests for AN sampling, and the factors affecting the test accuracy. Methods This single-center prospective study evaluated one qualitative (ESP) and two quantitative (LUMI and LUMI-P) rapid antigen tests using AN and NP swabs. Symptomatic patients aged 20 years or older, who were considered eligible for reverse-transcription quantitative polymerase chain reaction using NP samples within 9 days of onset were recruited. Sensitivity, specificity, and positive and negative concordance rates between AN and NP samples were assessed for the rapid antigen tests. We investigated the characteristics that affected the concordance between AN and NP sampling results. Results A total of 128 cases were recruited, including 28 positive samples and 100 negative samples. The sensitivity and specificity of AN samples using ESP were 0.81 and 1.00, while those of NP samples were 0.94 and 1.00. The sensitivity of AN and NP samples was 0.91 and 0.97, respectively, and specificity was 1.00, for both LUMI and LUMI-P. The positive concordance rates of AN to NP sampling were 0.87, 0.94, and 0.85 for ESP, LUMI, and LUMI-P, respectively. No factor had a significant effect on the concordance between the sampling methods. Conclusions ESP, LUMI, and LUMI-P showed practical diagnostic accuracy for AN sampling compared to NP sampling. There was no significant factor affecting the concordance between AN and NP sampling for these rapid antigen tests.

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

OBJECTIVES: 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% (κ = 0.37) and 72% vs 100% (κ = 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.

Immunochromatographic test for the detection of SARS-CoV-2 in saliva.

We evaluated the rapid immunochromatographic test for severe acute respiratory coronavirus 2 (SARS-CoV-2) antigen detection using 16 saliva specimens collected from 6 COVID-19 hospitalized patients, and detected N-antigen in 4 of 7 RT-PCR positive specimens. This POCT detected SARS-CoV-2 antigen in saliva and would be useful for COVID-19 diagnosis.

Evaluation of clinical utility of novel coronavirus antigen detection reagent, Espline® SARS-CoV-2.

BACKGROUND: To prevent the novel coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is necessary to perform early identification and isolation of people shedding the infectious virus in biological materials with high viral loads several days prior to symptom onset. Rapid antigen tests for infectious diseases are useful to prevent the pandemic spread in clinical settings. METHODS: We evaluated a SARS-CoV-2 antigen test, Espline® SARS-CoV-2 reagent, with reverse transcription polymerase chain reaction (RT-PCR) as reference test, using 129 nasopharyngeal swab specimens collected from COVID-19 hospitalized patients or from patients suspected having COVID-19-like symptoms. Out of these, 63 RT-PCR positive and 66 RT-PCR negative specimens were identified. RESULTS: Among 63 RT-PCR positive specimens, 25 were positive in the Espline test. Test sensitivity was estimated based on the 532.4 copies/reaction of SARS-CoV-2 RNA obtained through receiver operating characteristic analysis. When the specimens were classified based on time since symptom onset, Espline test sensitivity were 73.3% and 29.2% in specimens collected before day 9 and after day 10, respectively. CONCLUSION: Although the overall sensitivity of the Espline® SARS-CoV-2 reagent compared with RT-PCR is less, this antigen test can be useful in identifying people with high risk of virus transmission with high viral loads in order to prevent the pandemic and is useful for diagnosing COVID-19 within 30 min.

Clinical validation of quantitative SARS-CoV-2 antigen assays to estimate SARS-CoV-2 viral loads in nasopharyngeal swabs.

BACKGROUND: Expansion of the testing capacity for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important issue to mitigate the pandemic of coronavirus disease-2019 (COVID-19) caused by this virus. Recently, a sensitive quantitative antigen test (SQT), Lumipulse® SARS-CoV-2 Ag, was developed. It is a fully automated chemiluminescent enzyme immunoassay system for SARS-CoV-2. METHODS: In this study, the analytical performance of SQT was examined using clinical specimens from nasopharyngeal swabs using reverse transcription polymerase chain reaction (RT-PCR) as a control. RESULTS: Receiver operating characteristic analysis of 24 SARS-CoV-2-positive and 524 -negative patients showed an area under the curve of 0.957 ± 0.063. Using a cut-off value of 1.34 pg/ml, the sensitivity was 91.7%, the specificity was 98.5%, and the overall rate of agreement was 98.2%. In the distribution of negative cases, the 99.5 percentile value was 1.03 pg/ml. There was a high correlation between the viral load calculated using the cycle threshold value of RT-PCR and the concentration of antigen. The tendency for the antigen concentration to decrease with time after disease onset correlated with that of the viral load. CONCLUSIONS: Presented results indicate that SQT is highly concordant with RT-PCR and should be useful for the diagnosis of COVID-19 in any clinical setting. Therefore, this fully automated kit will contribute to the expansion of the testing capability for SARS-CoV-2.

Comparison of automated SARS-CoV-2 antigen test for COVID-19 infection with quantitative RT-PCR using 313 nasopharyngeal swabs, including from seven serially followed patients.

In routine clinical practice, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is determined by reverse-transcription PCR (RT-PCR). In the current pandemic, a more rapid and high-throughput method is in growing demand. Here, we validated the performance of a new antigen test (LUMIPULSE) based on chemiluminescence enzyme immunoassay. A total of 313 nasopharyngeal swabs (82 serial samples from 7 infected patients and 231 individual samples from 4 infected patients and 215 uninfected individuals) were analyzed for SARS-CoV-2 with quantitative RT-PCR (RT-qPCR) and then subjected to LUMIPULSE. We determined the cutoff value for antigen detection using receiver operating characteristic curve analysis and compared the performance of the antigen test with that of RT-qPCR. We also compared the viral loads and antigen levels in serial samples from seven infected patients. Using RT-qPCR as the reference, the antigen test exhibited 55.2% sensitivity and 99.6% specificity, with a 91.4% overall agreement rate (286/313). In specimens with > 100 viral copies and between 10 and 100 copies, the antigen test showed 100% and 85% concordance with RT-qPCR, respectively. This concordance declined with lower viral loads. In the serially followed patients, the antigen levels showed a steady decline, along with viral clearance. This gradual decline was in contrast with the abrupt positive-to-negative and negative-to-positive status changes observed with RT-qPCR, particularly in the late phase of infection. In summary, the LUMIPULSE antigen test can rapidly identify SARS-CoV-2-infected individuals with moderate to high viral loads and may be helpful for monitoring viral clearance in hospitalized patients.