From more testing to smart testing: Data-guided SARS-CoV-2 testing choices

19 October 2020

Rapid detection and isolation of new cases, combined with contact tracing and quarantine has become a critical pillar of the global efforts contain the COVID-19 pandemic. The purpose of this test, trace and isolate strategy is to stop transmission chains and reduce the impact of the disease. Epidemiological modelling suggests that aggressive test, trace and isolate strategy, combined with physical distancing and the use of personal protective equipment when physical distancing is not achievable, could suppress a second wave without the need for a prolonged lockdown.

Our research presents an in-depth analysis of data from drive through testing stations using rapid antigen detection tests, to assess their ability of to detect infectious cases. We show that the detection limits of five commercially available tests differ considerably, impacting the translation into the detection of infectious cases. We recommend careful fit-for-purpose testing before implementation of antigen rapid detection tests in routine testing algorithms as part of the COVID-19 response.

The advantage of faster time to result and therefore initiation of contact tracing is a great added benefit of rapid detection tests. In our example, routine application of these tests will increase the proportion of suspect cases who receive their test results the same day from 33 to 97%. The shortening of testing delays is a critical determinant of success of a contact tracing strategy, and shortening from 3 to 1 days can push expanding outbreaks into suppression. Our analysis also shows, however, that antigen rapid detection tests differ greatly in their ability to detect infectious cases, therefore requiring careful validation before routine application. In our setting, people were tested relatively soon after onset of disease, when viral loads are at their peak thus ensuring highest sensitivity of the tests. A more challenging application is the use of rapid detection tests in testing persons without symptoms, as a strategy to reopen society after lockdowns. Here, in the absence of knowledge of time since exposure, negative predictive values are difficult to assess and risk of false negatives is higher than in symptomatic persons that may be using physical distancing as is currently recommended globally. Nonetheless, when used judiciously, rapid detection testing offer hope to improve containment by more rapid isolation and contact tracing of the most infectious individuals.

Read preprint article here.

Authors: Janko van Beek, Zsofia Igloi, Timo Boelsums, Ewout Fanoy, Hannelore Gotz, Richard Molenkamp, Jeroen van Kampen, Corinne Geurtsvankessel, Annemiek van der Eijk, David van de Vijver, Marion Koopmans

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