COVID-19 assessment in family practice-A clinical decision rule based on self-rated symptoms and contact history.

The study aimed to evaluate the diagnostic accuracy of contact history and clinical symptoms and to develop decision rules for ruling-in and ruling-out SARS-CoV-2 infection in family practice. We performed a prospective diagnostic study. Consecutive inclusion of patients coming for COVID-PCR testing to 19 general practices. Contact history and self-reported symptoms served as index test. PCR testing of nasopharyngeal swabs served as reference standard. Complete data were available from 1141 patients, 605 (53.0%) female, average age 42.2 years, 182 (16.0%) COVID-PCR positive. Multivariable logistic regression showed highest odds ratios (ORs) for "contact with infected person" (OR 9.22, 95% CI 5.61-15.41), anosmia/ageusia (8.79, 4.89-15.95), fever (4.25, 2.56-7.09), and "sudden disease onset" (2.52, 1.55-4.14). Patients with "contact with infected person" or "anosmia/ageusia" with or without self-reported "fever" had a high probability of COVID infection up to 84.8%. Negative response to the four items "contact with infected person, anosmia/ageusia, fever, sudden disease onset" showed a negative predictive value (NPV) of 0.98 (95% CI 0.96-0.99). This was present in 446 (39.1%) patients. NPV of "completely asymptomatic," "no contact," "no risk area" was 1.0 (0.96-1.0). This was present in 84 (7.4%) patients. To conclude, the combination of four key items allowed exclusion of SARS-CoV-2 infection with high certainty. With the goal of 100% exclusion of SARS-CoV-2 infection to prevent the spread of SARS-CoV-2 to the population level, COVID-PCR testing could be saved only for patients with negative response in all items. The decision rule might also help for ruling-in SARS-CoV-2 infection in terms of rapid assessment of infection risk.