Site-of-care antigen testing (AgPOCT) can speed up testing for SARS-CoV-2. As some AgPOCTs become available, interest in their utility and performance grows. Here our objective was to compare the analytical sensitivity and specificity of seven commercially available AgPOCT devices.
In a single site laboratory evaluation study, we compared AgPOCT products from seven vendors: Abbott Panbio COVID-19 Ag Rapid Test, RapiGEN BIO CREDIT COVID-19 Ag Rapid Test, Healgen Coronavirus Ag Rapid Test Cassette (Swab ), the Coris BioConcept COVID-19 Ag Respi-Strip, the R-Biopharm RIDA QUICK SARS-CoV-2 Antigen, the nal von Minden NADAL COVID-19 Ag Test and the Roche-SD Biosensor SARS-CoV Rapid Antigen Test.
The tests were evaluated with recombinant SARS-CoV-2 nucleoprotein, cultured endemic and emerging coronaviruses, respiratory samples stored with known SARS-CoV-2 viral loads, stored samples from patients with respiratory pathogens other than SARS-CoV-2, and samples own swabs from healthy volunteers. We estimated analytical sensitivity in terms of approximate viral concentrations (quantified by real-time RT-PCR) that yielded positive AgPOCT results, and specificity in terms of propensity to generate false-positive results.
In 138 clinical specimens with quantified SARS-CoV-2 viral load, the 95% limit of detection (concentration at which 95% of the test results were positive) in six of seven AgPOCT products ranged from 2 · 07 × 106 and 2 · 86 × 107 copies per swab, with an outlier (RapiGEN) of 1 · 57 × 1010 copies per swab. The assays did not show cross-reactivity with cell cultures or tissue culture supernatants containing any of the four endemic human coronaviruses (HCV-229E, HCV-NL63, HCV-OC43, or HCV-HKU1) or MERS-CoV, with the exception of the Healgen Assay in a repeat test on the HCV-HKU1 supernatant.
All trials cross-detected SARS-CoV. The accumulated specificities between the clinical samples stored with infections other than SARS-CoV-2 (n = 100) and the self-samples from healthy volunteers (n = 35; accumulated sample n = 135) ranged between 98 5% (95% CI 94 · 2-99 · 7) and 100 · 0% (97 · 2–100 · 0) in five products, with two outliers in 94 · 8% (89 · 2-97 · 7; R-Biopharm) and 88 · 9% (82 · 1–93 · 4; Healgen). False-positive results do not appear to be associated with any specific respiratory pathogens.
The sensitivity range of most AgPOCTs overlaps with the SARS-CoV-2 viral loads typically seen in the first week of symptoms, which marks the infectious period in most patients. AgPOCTs with detection limits that approximate the virus concentrations at which patients are infectious could allow shortcuts in decision-making in various areas of medical care and public health.
EU Horizon 2020 Research and Innovation Program, German Ministry of Research, German Federal Ministry of Economy and Energy, German Ministry of Health, and the Bill and Melinda Gates Foundation.