Evaluation of Rapid Antigen Tests Using Nasal Samples to Diagnose SARS-CoV-2 in Symptomatic Patients

Abstract

IntroductionThe best way to mitigate an outbreak besides mass vaccination is via early detection and isolation of infected cases. As such, a rapid, cost-effective test for the early detection of COVID-19 is required.MethodsThe study included 4,183 mildly symptomatic patients. A nasal and nasopharyngeal sample obtained from each patient was analyzed to determine the diagnostic ability of the rapid antigen detection test (RADT, nasal swab) in comparison with the current gold-standard (RT-PCR, nasopharyngeal swab).ResultsThe calculated sensitivity and specificity of the RADT was 82.1 and 99.1%, respectively. Kappa's coefficient of agreement between the RADT and RT-PCR was 0.859 (p < 0.001). Stratified analysis showed that the sensitivity of the RADT improved significantly when lowering the cut-off RT-PCR Ct value to 24.ConclusionOur study's results support the potential use of nasal swab RADT as a screening tool in mildly symptomatic patients, especially in patients with higher viral loads.

Rapid screening of SARS-CoV-2 infection: Good performance of nasopharyngeal and Nasal Mid-Turbinate swab for antigen detection among symptomatic and asymptomatic individuals

“…The overall sensitivities obtained were 84.4% with NMTS and 88.9% with NPS. In addition, the performance in our study is corroborated by Alqahtani et al [ 12 ]. They evaluated the analytical accuracy of the Panbio Ag-RDT in nasal swab specimens in a group of patients with mild symptoms, with reference to the real time RT-PCR in NPS samplings, and the calculated sensitivity and specificity were 82.1% and 99.1%, respectively.…”

“…Besides, when samples were divided into sub-groups according to the Ct values, all samples with RT-PCR Ct-values <25 were detectable by the Panbio Ag-RDT with both sampling techniques. Furthermore, it yielded a greater number of discordant results among patients with Ct≥ 30, consistent with findings of previous studies that assessed the Abbott Ag-RDT in different specimen types, but also with reports of commercial Ag-RDTs from other suppliers [ 6 , 7 , 12 , 15 , 16 , 18 – 28 ]. These results could also be observed when a double stratification of the samples was performed (according to their Ct values and the presence of symptoms) ( S2 Table ).…”

De-isolation of vaccinated COVID-19 health care workers using rapid antigen detection test

“…Several studies evaluated the performance of different RADT compared to RT-PCR and viral cultures [6] , [13] , [14] , [15] . A study of 206 COVID-19 samples compared the sensitivity and specificity of 4 different RADT to SARS-CoV-2 viral cultures.…”

Performance and application evaluation of SARS‐CoV‐2 antigen assay

“… 30 Further stratified analysis showed that when the critical value of the real‐time (RT)‐PCR cycle threshold ( C t ) was reduced to 24, the sensitivity of the SARS‐CoV‐2 antigen assay was significantly improved. 31 Additionally, the detection rate is related to the time of onset. The sensitivity of the samples collected 0–1 days after symptom onset increased from 79.6% to 86.4% when the samples collected 4–5 days after symptom onset were grouped.…”

“…In a prospective observational study conducted in Spain, it was found that the sensitivity of the SARS‐CoV‐2 antigen assay increased with increasing SARS‐CoV‐2 RNA load, reaching 95.6% in samples with a virus load ≥ 7.5 log10 copies/ml ( C t ≤ 20) 30 . Further stratified analysis showed that when the critical value of the real‐time (RT)‐PCR cycle threshold ( C t ) was reduced to 24, the sensitivity of the SARS‐CoV‐2 antigen assay was significantly improved 31 . Additionally, the detection rate is related to the time of onset.…”