Performance of Existing and Novel Surveillance Case Definitions for COVID-19 in the Community

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), presents with a broad range of symptoms. Existing COVID-19 case definitions were developed from early reports of severely ill, primarily hospitalized, patients. Symptom-based case definitions that guide public health surveillance and individual patient management in the community must be optimized for COVID-19 pandemic control. Methods: We collected daily symptom diaries and performed RT-PCR on respiratory specimens over a 14-day period in 185 community members exposed to a household contact with COVID-19 in the Milwaukee, Wisconsin and Salt Lake City, Utah metropolitan areas. We interpreted the discriminatory performance (sensitivity, specificity, predictive values, F-1 score, Youden9s index, and prevalence estimation) of individual symptoms and common case definitions according to two principal surveillance applications (i.e., individual screening and case counting). We also constructed novel case definitions using an exhaustive search with over 73 million symptom combinations and calculated bias-corrected and accelerated bootstrap confidence intervals stratified by children versus adults. Findings: Common COVID-19 case definitions generally showed high sensitivity (86-96%) but low positive predictive value (PPV) (36-49%; F-1 score 52-63) in this community cohort. The top performing novel symptom combinations included taste or smell dysfunction. They also improved the balance of sensitivity and PPV (F-1 score 78-80) and reduced the number of false positive symptom screens. Performance indicators were generally lower for children (<18 years of age). Interpretation: Existing COVID-19 case definitions appropriately screened in community members with COVID-19. However, they led to many false positive symptom screens and poorly estimated community prevalence. Absent unlimited, timely testing capacity, more accurate case definitions may help focus public health resources. Novel symptom combinations incorporating taste or smell dysfunction as a primary component better balanced sensitivity and specificity. Case definitions tailored specifically for children versus adults should be further explored.