Toward a COVID-19 testing policy: where and how to test when the purpose is to isolate silent spreaders

Rivas, A. L.; Hoogesteijn, A. L.; Hittner, J.; van Regenmortel, M. H.; Kempaiah, P.; Vogazianos, P.; Antoniades, A.; Febles, J. P.; Fasina, F. O.

Background To stop pandemics, such as COVID 19, infected individuals should be detected, treated if needed, and to prevent contacts with susceptible individuals- isolated. Because most infected individuals may be asymptomatic, when testing misses such cases, epidemics may growth exponentially, inducing a high number of deaths. In contrast, a relatively low number of COVID 19 related deaths may occur when both symptomatic and asymptomatic cases are tested. Methods To evaluate these hypotheses, a method composed of three elements was evaluated, which included: (i) county and country level geo-referenced data, (ii) cost benefit related considerations, and (iii) temporal data on mortality or test positivity (TP). TP is the percentage of infections found among tested individuals. Temporal TP data were compared to the tests/case ratio (T/C ratio) as well as the number of tests performed/million inhabitants (tests/mi) and COVID-19 related deaths/million inhabitants (deaths/mi). Findings Two temporal TP profiles were distinguished, which, early, displayed low (~ 1 %) and/or decreasing TP percentages or the opposite pattern, respectively. Countries that exhibited >10 TP % expressed at least ten times more COVID-19 related deaths/mi than low TP countries. An intermediate pattern was identified when the T/C ratio was explored. Georeferenced, TP based analysis discovered municipalities where selective testing would be more cost effective than alternatives. Interpretations When TP is low and/or the T/C ratio is high, testing detects asymptomatic cases and the number of COVID 19 related deaths/mi is low. Georeferenced TP data can support cost-effective, site specific policies. TP promotes the prompt cessation of epidemics and fosters science based testing policies.