Table 4 Examples from included studies

Study design: representative recruitment

Representative participants

• Community infection

• Contact tracing including asymptomatic

• Hospitalised patients

Population surveillance of Italian town, with PCR testing across [39]

Contact tracing [9, 30, 34]

Retrospective cohort of 96 hospitalised patients [38]

Study design: planned testing and follow-up

Informative sampling

• Multiple sampling sites per participant

• Planned schedule of sampling

• Sampling continues after negative test results

• Sampling continues after hospital discharge

Three samples per patient, multiple testing including prolonged testing even after multiple negative results [10]

Population surveillance of Italian town over 18 days [39]

Long follow-up post-hospital [16, 35, 36]

Planned schedule of testing ([30], asymptomatic contact tracing follow-up [36,37,38])

Study design: sampling

Reporting of sampling methods (sample site, staff conducting test, sample volumes, and methods)

Most studies had very sparse reporting of sample collection methods.

Example of fuller reporting [40]

Individual participant data reporting for sharing

Examples of plots and tables that facilitated sharing of individual participant data

Retrospective cohort of 96 patients all tested with sputum, faeces, and blood. Plot shows time span of positive test results, hospitalisation timing, and disease severity for individual patients [38]

Data showing time course of illness with PCR test results [9, 31]

Data showing RT-PCR test results by patient and time point [10]

Viral load over time [15]