Routine SARS-CoV-2 Testing Frequency and Risk of Severe COVID-19: A Nationwide Population-Based Study

OBJECTIVES: This study assessed whether higher routine SARS-CoV-2 testing frequency is associated with reduced risk of severe, critical, or fatal COVID-19. METHODS: A nationwide matched case-control study was conducted in Qatar between February 5, 2020 and December 18, 2021, comparing 10,909 severe, critical, or fatal COVID-19 cases to 98,811 controls from Qatar's population. Associations between testing frequency (three- and two-level classifications) and severe outcomes were estimated using conditional logistic regression. RESULTS: Higher routine SARS-CoV-2 testing frequency was not associated with reduced odds of severe, critical, or fatal COVID-19. In the three-level classification analysis, aORs were 1.03 (95% CI, 0.97-1.10) for intermediate and 0.86 (95% CI, 0.74-1.01) for high versus low testing frequency. In the two-level classification analysis, the aOR was 0.97 (95% CI, 0.88-1.07) for high versus low testing frequency. Findings were consistent across subgroup analyses among clinically vulnerable individuals, outcome-stratified analyses by severity level, and sensitivity analyses restricted to Qatari nationals and the earliest severity episode per individual. CONCLUSIONS: Greater routine testing was not associated with reduced individual-level risk of progression to severe COVID-19, supporting more targeted allocation of testing resources while preserving the public health value of testing for case identification and transmission control.