SARS-CoV-2/COVID-19 Testing: The Tower of Babel

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Chiara Reno
Jacopo Lenzi
Davide Golinelli
Davide Gori
Carlo Signorelli
John Kraemer
Michael A. Stoto
Elisa Avitabile
Maria Paola Landini
Tiziana Lazzarotto
Maria Carla Re
Paola Rucci
Gloria Taliani
Davide Trerè
Caterina Vocale
Maria Pia Fantini


COVID-19, SARS-CoV-2, Pandemic, Molecular Diagnostic Techniques, Rapid Antigen Test, Pooling Test, Predictive Value of Tests, Public Health Surveillance, Screening


Background and aim: Testing represents one of the main pillars of public health response to SARS-CoV-2/COVID-19 pandemic. This paper shows how accuracy and utility of testing programs depend not just on the type of tests, but on the context as well.

Methods: We describe the testing methods that have been developed and the possible testing strategies; then, we focus on two possible methods of population-wide testing, i.e., pooled testing and testing with rapid antigen tests. We show the accuracy of split-pooling method and how, in different pre-test probability scenarios, the positive and negative predictive values vary using rapid antigen tests.

Results: Split-pooling, followed by retesting of negative results, shows a higher sensitivity than individual testing and requires fewer tests. In case of low pre-test probability, a negative result with antigen test could allow to rule out the infection, while, in case of a positive result, a confirmatory molecular test would be necessary.

Conclusions: Test performance alone is not enough to properly choose which test to use; goals and context of the testing program are essential. We advocate the use of pooled strategies when planning population-wide screening, and the weekly use of rapid tests for close periodic monitoring in low-prevalence populations.


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