ABSTRACT
Introduction: Rapid qualitative antigen testing has been widely used for the laboratory diagnosis of COVID-19 with nasopharyngeal samples. Saliva samples have been used as alternative samples, but the analytical performance of those samples for qualitative antigen testing has not been sufficiently evaluated. Methods: A prospective observational study evaluated the analytical performance of three In Vitro Diagnostics (IVD) approved COVID-19 rapid antigen detection kits for saliva between June 2022 and July 2022 in Japan using real-time reverse transcription polymerase chain reaction (RT-PCR) as a reference. A nasopharyngeal sample and a saliva sample were simultaneously obtained, and RT-PCR was performed. Results: In total, saliva samples and nasopharyngeal samples were collected from 471 participants (140 RT-PCR-positive saliva samples and 143 RT-PCR-positive nasopharyngeal samples) for the analysis. The median Ct values were 25.5 (interquartile range [IQR]: 21.9-28.8) for saliva samples and 17.1 (IQR: 15.5-18.7) for nasopharyngeal samples (p<0.001). Compared with saliva samples of RT-PCR, the sensitivity and specificity were 46.4% and 99.7% for ImunoAce SARS-CoV-2 Saliva, 59.3% and 99.1% for Espline SARS-CoV-2 N, and 61.4% and 98.8% for QuickChaser Auto SARS-CoV-2, respectively. The sensitivity is >90% for saliva samples with a moderate-to-high viral load (Ct<25), whereas the sensitivity is <70% for high-viral-load nasopharyngeal samples (Ct<20). Conclusion: COVID-19 rapid antigen detection kits with saliva showed high specificities, but the sensitivities varied among kits, and the analytical performance of saliva qualitative antigen detection kits was much worse than that of kits using nasopharyngeal samples.
ABSTRACT
IntroductionAntigen testing is essential in the clinical management of COVID-19. However, most evaluations of antigen tests have been performed before the emergence of the Omicron variant. Thus, an assessment of the diagnostic performance of antigen tests for the detection of SARS-CoV-2 during the circulation of Omicron variant is required. MethodsThis prospective observational study evaluated QuickNavi-COVID19 Ag, a rapid antigen detection test between December 2021 and February 2022 in Japan, using real-time reverse transcription (RT)-PCR as a reference. Two nasopharyngeal samples were simultaneously collected for antigen testing and for RT-PCR. Variant analysis of the SARS-CoV-2 genomic sequencing was also performed. ResultsIn total, nasopharyngeal samples were collected from 1,073 participants (417 positive; 919 symptomatic; 154 asymptomatic) for analysis. Compared with those of RT-PCR, the sensitivity, specificity, positive predictive value, and negative predictive value were 94.2% (95% CI: 91.6%-96.3%), 99.5% (95% CI: 98.7%-99.9%), 99.2% (95% CI: 97.8%-99.8%), and 96.5% (95% CI: 94.8%-97.7%), respectively. The sensitivity among symptomatic individuals was 94.3% (95% CI: 91.5%-96.4%). Overall, 85.9% of sequences were classified as Omicron sublineage BA.1, 12.4% were Omicron sublineage BA.2, and 1.6% were Delta B.1.617.2. (Delta variant). Most of the samples (87.1%) had Ct values <25. ConclusionsThe QuickNavi-COVID19 Ag test showed high diagnostic performance for the detection of the SARS-CoV-2 Omicron sublineages BA.1 and BA.2 from nasopharyngeal samples.
ABSTRACT
Background and ObjectivePoint-of-care type molecular diagnostic tests have been used for detecting SARS-CoV-2, although their clinical utility with nasal samples has yet to be established. This study evaluated the clinical performance of the cobas Liat SARS-CoV-2 & Influenza AB (Liat) in nasal samples. MethodsNasal and nasopharyngeal samples were collected and were tested using the Liat, the cobas 6800 system and the cobas SARS-CoV-2 & Influenza AB (cobas), and a method developed by National Institute of Infectious Diseases, Japan (NIID). ResultsA total of 814 nasal samples were collected. The Liat assay was positive for SARS-CoV-2 in 113 (13.9%). The total, positive, and negative concordance rate between the Liat and cobas/NIID assays were 99.3%/98.4%, 99.1%/100%, and 99.3%/98.2%, respectively. Five samples were positive only using the Liat assay. Their Ct values ranged from 31.9 to 37.2. The Ct values of the Liat assay were significantly lower (p < 0.001) but were correlated (p < 0.001) with those of other molecular assays. In the participants who tested positive for SARS-CoV-2 on the Liat assay using nasopharyngeal samples, 88.2% of their nasal samples also tested positive using the Liat assay. ConclusionThe Liat assay showed high concordance with other molecular assays in nasal samples. Some discordance occurred in samples with Ct values > 30 on the Liat assay. Key PointsO_LIThe cobas Liat SARS-CoV-2 & Influenza AB assay showed high concordance with other molecular assays in nasal and nasopharyngeal samples, providing results within 20 minutes. C_LIO_LISome discordance occurred in samples with Ct values > 30 on the Liat assay. C_LIO_LIThe Liat assay may be suitable for use in a variety of clinical situations, primarily where accurate detection of SARS-CoV-2 is necessary. C_LI
ABSTRACT
IntroductionSince respiratory sample collection is an uncomfortable experience, simultaneous detection of pathogens with a single swab is preferable. We prospectively evaluated the clinical performance of a newly developed antigen test QuickNavi-Flu+COVID19 Ag (Denka Co., Ltd., Tokyo, Japan) which can detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses at the same time with a single testing device. MethodsIncluded were those who were suspected of contracting coronavirus disease 2019 (COVID-19) and referred to a PCR center at Ibaraki prefecture in Japan, between August 2, 2021 to September 13, 2021, when the L452R mutant strains of SARS-CoV-2 were prevalent. Additional nasopharyngeal samples and anterior nasal samples were obtained for the antigen test and were compared with a reference reverse transcription PCR (RT-PCR) using nasopharyngeal samples. ResultsIn total, 1510 nasopharyngeal samples and 862 anterior nasal samples were evaluated. For SARS-CoV-2 detection in nasopharyngeal samples, the sensitivity and specificity of the antigen test were 80.9% and 99.8%, respectively. The sensitivity and specificity using anterior nasal samples were 67.8% and 100%, respectively. In symptomatic cases, the sensitivities increased to 88.3% with nasopharyngeal samples and 73.7% with anterior nasal samples. There were three cases of discrepant results between the antigen test and the real-time RT-PCR. All of them were positive with the antigen test but negative with the real-time RT-PCR in SARS-CoV-2 detection. During the study period, influenza viruses were not detected. ConclusionA combo kit, QuickNavi-Flu+COVID19 Ag, showed an acceptable sensitivity and sufficient specificity for SARS-CoV-2 detection, especially using nasopharyngeal sample collected from symptomatic patients.
