SARS-CoV-2 testing strategy: A comparison of restricted and extended strategies in a Swiss outpatient cohort from the community and hospital employees.

Background: Testing is a key measure to control the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we empirically compared two SARS-CoV-2 testing strategies.

Methods: We used data from a Swiss single-centre, outpatient cohort study (n = 6,331 test results). A "restricted" strategy was applied to individuals with respiratory symptoms and/or fever and selected risk factors, or an epidemiological link and an "extended" strategy included any clinical symptoms without restriction, irrespective of risk factors and exposure. Data on infection, symptoms, viral load were collected during the first wave (March 11-April 21, 2020) and patients were followed up for clinical complications and hospitalisations until August 31, 2020.

Findings: Infection, clinical complications, and hospitalisation rates were lower for those in the extended strategy compared with the restricted strategy (17.2% vs. 25.0%, 12.3% vs. 20.8%, and 0.7% vs. 2.3%). In the whole cohort, participants included in the extended strategy had a lower number of symptoms (3.51 vs. 4.57; p < .001) and visits occurred earlier after symptom onset (0-3 days: 59.2% vs. 44.2%; p < .001). Among positive cases, the viral load was higher for the extended strategy (p < .001).

Conclusions: These findings highlighted the crucial importance to implement a widespread testing strategy to achieve a better understanding of the infection, to mount an effective control response, by capturing people when their viral load is highest. A widespread test strategy should be available without barriers to help break the chains of transmission.