From more testing to smart testing: data-guided SARS-CoV-2 testing choices, the Netherlands, May to September 2020

Abstract

BackgroundSARS-CoV-2 RT-PCR assays are more sensitive than rapid antigen detection assays (RDT) and can detect viral RNA even after an individual is no longer infectious. RDT can reduce the time to test and the results might better correlate with infectiousness.AimWe assessed the ability of five RDT to identify infectious COVID-19 cases and systematically recorded the turnaround time of RT-PCR testing.MethodsSensitivity of RDT was determined using a serially diluted SARS-CoV-2 stock with known viral RNA concentration. The probability of detecting infectious virus at a given viral load was calculated using logistic regression of viral RNA concentration and matched culture results of 78 specimens from randomly selected non-hospitalised cases. The probability of each RDT to detect infectious cases was calculated as the sum of the projected probabilities for viral isolation success for every viral RNA load found at the time of diagnosis in 1,739 confirmed non-hospitalised COVID-19 cases.ResultsThe distribution of quantification cycle values and estimated RNA loads for patients reporting to drive-through testing was skewed to high RNA loads. With the most sensitive RDT (Abbott and SD Biosensor), 97.30% (range: 88.65-99.77) of infectious individuals would be detected. This decreased to 92.73% (range: 60.30-99.77) for Coris BioConcept and GenBody, and 75.53% (range: 17.55-99.77) for RapiGEN. Only 32.9% of RT-PCR results were available on the same day as specimen collection.ConclusionThe most sensitive RDT detected infectious COVID-19 cases with high sensitivity and may considerably improve containment through more rapid isolation and contact tracing.

Keywords: SARS-CoV-2; infectiousness; public health policy; rapid detection test.

Figure 1

SARS-CoV-2 RNA load by time since onset for RT-PCR-positive samples at a drive-through test station, Rotterdam, the Netherlands, 26 May–5 September 2020 (n = 1,450^a)

Figure 2

Viral RNA loads at time of diagnosis of community cases with RT-PCR-confirmed SARS-CoV-2 infection presenting to a drive through test station, Rotterdam, the Netherlands, 26 May–5 September 2020 (n = 1,754^a)