Antigen rapid tests, nasopharyngeal PCR and saliva PCR to detect SARS-CoV-2: a prospective comparative clinical trial

Abstract

BackgroundNasopharyngeal antigen Rapid Diagnostic Tests (RDTs) and saliva RT-PCR have shown variable performance to detect SARS-CoV-2.MethodsIn October 2020, we conducted a prospective trial involving patients presenting at testing centers with symptoms of COVID-19. We compared detection rates and performance of RDT, saliva PCR and nasopharyngeal (NP) PCR.ResultsOut of 949 patients enrolled, 928 patients had all three tests. Detection rates were 35.2% (95%CI 32.2-38.4%) by RDT, 39.8% (36.6-43.0%) by saliva PCR, 40.1% (36.9-43.3%) by NP PCR, and 41.5% (38.3-44.7%) by any test. For those with viral loads (VL) ≥106 copies/ml, detection rates were 30.3% (27.3-33.3), 31.4% (28.4-34.5), 31.5% (28.5-34.6), and 31.6% (28.6-34.7%) respectively.Sensitivity of RDT compared to NP PCR was 87.4% (83.6-90.6%) for all positive patients and 96.5% (93.6-98.3%) for those with VL≥106. Sensitivity of STANDARD-Q®, Panbio™ and COVID-VIRO® Ag tests were 92.9% (86.4-96.9%), 86.1% (78.6-91.7%) and 84.1% (76.9-89.7%), respectively. For those with VL≥106, sensitivities were 96.6% (90.5-99.3%), 97.8% (92.1-99.7%) and 95.3% (89.4-98.5%) respectively. Specificity of RDT was 100% (99.3-100%) compared to any PCR. RDT sensitivity was similar <4 days (87.8%) and ≥4 days (85.7%) after symptoms onset (p=0.6). Sensitivities of saliva and NP PCR were 95.7% (93.1-97.5%) and 96.5% (94.1-98.1%), respectively, compared to the other PCR.ConclusionsThe high performance of RDTs allows rapid identification of COVID cases with immediate isolation of the vast majority of contagious individuals. RDT could be a game changer in primary care practices, and even more so in resource-constrained settings. PCR on saliva can replace NP PCR.ClinicalTrial.gov Identifier: NCT04613310

ImplemeNting SARS-CoV-2 Rapid antigen testing in the Emergency wArd of a Swiss univErsity hospital: the INCREASE study

“…We also carried out a performance assessment and comparison between four antigen tests. Our results showed a significantly lower overall detection rate of SARS-CoV-2 infections compared to the previous validation we performed in Lausanne, and compared to other studies 8,18,19 .…”

Head-to-head comparison of SARS-CoV-2 antigen-detecting rapid test with professional-collected nasalversusnasopharyngeal swab

“…In patients with high viral load (>7.0 log 10 SARS-CoV2 RNA copies/swab), the sensitivity of the Ag-RDT with NMT-sampling was 100% (19/19 PCR positives detected; 95% CI 83.9-100) and 94.7% (18/19 PCR positives detected; 95% CI 76.4-99.7) with NPsampling. In contrast, the Ag-RDT more frequently did not detect patients with lower viral load or with symptoms >7 days (Table 1), as commonly observed in studies on Ag-RDTs [7,8].…”

Diagnostic performance of a SARS-CoV-2 rapid antigen test in a large, Norwegian cohort

“…Recent large prospective studies on the Panbio RAT have included from 913 to 4138 participants and were performed in settings with relatively high SARS-CoV-2 prevalence, ranging from 9.6 % to 40.1 % ( [6] , [7] , [8] , [9] , [10] , [11] , [12] ). The prevalence in Oslo during the study period was low to medium with a prevalence rate in all samples from Aker test station at 5.7 % (unpublished data), which made it particularly important to conduct an independent evaluation.…”