Testing has not been as effective as it could have been in controlling the global pandemic because it has been too inaccessible, too slow to give results, and too expensive. If tests had been universally accessible, quick and cheap, the pandemic could have been controlled more quickly, and disruption to society could have been minimized. Why do we not have such tests? The answer is that we may have them – but have not been using them in quite the right way. Rapid antigen tests – not applied just once, or with substantial gaps in time, but more than once in rapid succession. For instance, if we interpret a repeated test result as positive overall when at least one of two immediately repeated tests is positive, sensitivity levels of rapid antigen tests can very likely be raised to the level of PCR tests (i.e. the proportion of false negatives can be lowered to a negligible level). The underlying reasoning involves only elementary mathematics. Rapid antigen tests are also more relevant for many clinical and public health applications, since a positive result on such tests is very likely more correlated with an individual actually being infective. In combination with other methods, the strategy of “Parallel Rapid Testing” offers an approach to testing that can be applied immediately and on a widespread basis, for potentially considerable societal benefit. Testing for Covid-19 is likely for to be needed for the foreseeable future, as universal vaccination and population-level immunity remain distant. The proposed strategy may be useful for future pandemics too.
Download the draft paper (joint with Dr. Saumya Das of Harvard Medical School and Massachusetts General Hospital) via MedRXiv here.
Download spreadsheet with supporting calculations here.