Baseline and follow-up assessments
ADVERSE EVENTS, RECRUITMENT
In addition to undergoing testing for the index test(s) and reference standard described below, further participant information was collected at the time of recruitment using an electronic case report form (eCRF). Variables included age, sex, ethnicity, presence and duration of specified symptoms within the preceding 14 days, vaccine status, household contacts diagnosed with SARS-CoV-2, and the timing and results of previous tests for SARS-CoV-2. Adult participants (age ≥ 16 years) recruited from general practices were asked to provide a venous blood sample for antibody testing, collected by appropriately trained staff. These participants were also invited to attend a second visit, or be visited at home by a research nurse, after 28 days to provide a second sample for repeat antibody testing. Adult participants were asked to complete an online daily symptom diary for 28 days after recruitment, but as completion rates were low, no diary data are reported here. Linked electronic health records provided collateral information about subsequent hospitalisation, SARS-CoV-2 test results (in addition to those performed for this study) and mortality within 28 days. Serious adverse events related to test usage were reported by study sites to the RAPTOR-C19 coordination centre via adverse events reporting forms, which were evaluated by clinical staff.