COVID-19 case definitions, diagnostic testing criteria, and surveillance across the pandemic's 25 highest burden countries

Suthar, A.; Schubert, S.; Garon, J.; Couture, A.; Brown, A.; Charania, S.

Objective: We compared suspect, probable, and confirmed case definitions, as well as diagnostic testing criteria, used in the COVID-19 pandemic's 25 highest burden countries to aid interpretation of global and national surveillance data. Methods: We identified the COVID-19 pandemic's 25 countries with the highest disease burden based on the number of cumulative reported cases to the World Health Organization (WHO) as of 1 October 2020. We searched official websites of these countries for suspect, probable, and confirmed case definitions. Given that confirmation of COVID-19 usually requires diagnostic testing, we also searched for diagnostic testing eligibility criteria in these countries. Extracted case definitions and testing criteria were managed in a database and analyzed in Microsoft Excel. Findings: We identified suspect, probable, and confirmed case definitions in 96%, 64%, and 100% of countries, respectively. Testing criteria were identified in 100% of countries. 56% of identified countries followed WHO recommendations for using a combination of clinical and epidemiological criteria as part of the suspect case definition. 75% of identified countries followed WHO recommendations on using clinical, epidemiological, and diagnostic criteria for probable cases. 72% of countries followed WHO recommendations on using PCR testing for confirming a case of COVID-19. Finally, 64% of countries used testing eligibility criteria at least as permissive as WHO. Conclusion: There is marked heterogeneity in who is eligible for testing in countries and how countries define a case of COVID-19. This affects the ability to compare burden, transmission, and response impact estimates derived from case surveillance data across countries.