Table 1

Study structure

Severity stageCaseControlPopulation
1. InfectionTest positiveTest negativeGeneral population
2. Severe symptoms (clinically or radiologically)Severe symptomsNon-severe symptomsHospitalised COVID-19 cases
3. ICU admittanceAdmitted to ICUNot admitted to ICUHospitalised COVID-19 cases
4. DeathDeathAliveHospitalised COVID-19 cases
  • ICU, intensive care unit.