Analytical and Clinical Performance of the Panbio COVID-19 Antigen-Detecting Rapid Diagnostic Test

Abstract

Background The current standard for COVID-19 diagnosis, RT-qPCR, has important drawbacks for its use as a tool for epidemiological control, including the need of laboratory-processing, high cost, and long turnaround from sampling to results release. Antigen-based rapid diagnostic tests (Ag-RDT) provide a promising alternative for this purpose. Methods We assessed the analytical and clinical performance of the Ag-RDT Panbio COVID-19 Ag Test (Abbott), using RT-qPCR as a reference test. The clinical performance was assessed using nasopharyngeal swabs, collected in routine practice for case confirmation and contact tracing, and nasal mid-turbinate swabs, collected in preventive screenings of asymptomatic individuals. Fresh samples were analysed by RT-q-PCR, stored at -80 C, and analysed using the Ag-RDT according to the manufacturer instructions. Findings The Ag-RDT had a limit of detection of 6.5 *105 copies/reaction. The clinical performance was assessed on 1,406 frozen swabs with a PCR result available: 951 (67.7%) positive and 455 (32.4%) negative. The Ag-RDT identified the presence of SARS-CoV-2 in 872 of 951 PCR-positive samples (91.7%; 95% CI 89.8-93.4 and ruled out its presence in 450 of 455 PCR-negative samples (specificity 98.9%; 95% CI 97.5 - 99.6). Sensitivity increased in samples with lower Ct values (Ct <25, 98.2%; Ct<30, 94.9%) and was higher among symptomatic cases (92.6%) and their contacts (94.2%) than among asymptomatic individuals (79.5%). In the setting of asymptomatic screening, sensitivity also increased with lower Ct values (Ct <25, 100%; Ct<30, 98.6%). Assuming a pre-test probability of 5%, the negative and positive predictive values were 99.6% (99.5 - 99.6) and 81.5% (65.0 - 93.2), respectively. Interpretation The Panbio COVID-19 Ag-RDT has high sensitivity for detecting the presence of SARS-CoV-2 in nasal or nasopharyngeal swabs of both, symptomatic and asymptomatic individuals. The diagnostic performance of the test is particularly good in samples with viral loads associated with high risk of viral transmission (Ct <25), which show high positive and negative predictive values even when assuming a prevalence as low as 5%.

Diagnostic performance of CerTest and Panbio antigen rapid diagnostic tests to diagnose SARS-CoV-2 infection

“…Because of that, Ag-RDTs cannot be considered as a replacement to RT-PCR, but a complement for the diagnosis of SARS-CoV-2 infection. On the other hand, some authors have pointed out that these tests can be useful also for asymptomatic individuals with high viral loads, being particularly useful in situations of high prevalence of the disease [ 24 ]. These results would mean that Ag-RDTs could be used as a screening tool in asymptomatic populations to detect individuals with high infectious capacity.…”

Panbio™ rapid antigen test for SARS-CoV-2 has acceptable accuracy in symptomatic patients in primary health care

“…A study in France that examined positive and negative frozen RT-PCR samples reported a much lower overall sensitivity of only 35.3% 18 ; however, test sensitivity was greater in samples collected within 3 days since the onset of the symptoms and in samples from patients with high viral loads. Two preprints (non peer-reviewed studies) reported test sensitivities of 91.7% 19 and 97.1% 10 . An evaluation report in Spain performed in symptomatic patients who visited hospital emergency rooms reported a sensitivity of 98.2% 20 .…”

Impact of mass testing during an epidemic rebound of SARS-CoV-2: a modelling study using the example of France

“…The development of rapid antigen tests facilitates the implementation of such an approach since these tests can provide results in less than 30 min compared with 1-2 days for the standard PCR. Although these antigen tests have a lower sensitivity than the PCR test for the diagnostics of SARS-CoV-2, the most sensitive rapid antigen tests have a sensitivity threshold that is sufficient to identify a large proportion of infectious individuals with high viral shedding, ranging from 75 to 97% depending on the test [2,3]. However, even with antigen tests, the implementation of mass testing will be challenging, with an impact that is still to be determined.…”

“…has a probability of testing positive with an antigenic test equal to the sensitivity Se = 90% [2,3] and that a person testing positive will, thanks to self-isolation, reduce onward transmissions by ρ = 70% on average. In sensitivity analyses, we also considered Se = 60% or 75% and ρ = 50% or 90%.…”