| Bias | Author's judgement | Support for judgement |
| Confounding |
Serious |
Some comorbidities (e.g. COPD) and sex are not controlled for. They are balanced at baseline. Ethnicity or socio-economic status is neither controlled for nor reported. |
| Selection of participants into the study |
Serious |
Quote: "Exposure to corticosteroids was defined as the use of intravenous steroids at any time during the hospital admission." "There were patients who were receiving prior steroid treatment due to chronic conditions (typically oral steroids). If steroid doses were modified with the aim of treating COVID, they were included as cases. If they continued with their usual steroid dose, they were included as controls." Comment: Start of follow up and start of intervention do not coincide for all participants. A potentially important amount of follow-up time is missing from analyses. |
| Intervention classification |
Low |
Quote: “Epidemiological, clinical, laboratory and radiologic data, including concomitant COVID-19 treatments, were extracted from electronic medical records (SELENE System, Cerner Iberia, S.L.U., Madrid [Spain]) using a standardized data collection form. All data were included by a primary reviewer and subsequently checked by two senior physicians.”
“Exposure to corticosteroids was defined as the use of intravenous steroids at any time during the hospital admission. Patients with steroid treatment were designated as the “treatment cohort”, and those who did not receive them as “control cohort”.” Comment: Treatment groups were classified using clearly defined criteria. |
| Deviation from intended intervention |
NI |
Comment: The information reported is inadequate to assess whether there are deviations from the intended intervention beyond what would be expected in usual practice. |
| Missing data |
Low |
Comment: No participants were excluded due to missing outcome data or missing data on other variables needed for the analysis. Risk assessed to be low for the outcomes: time to death, all-cause mortality. |
| Measurements of outcomes |
Low |
Comment: Observer-reported outcome (death). Risk assessed to be low for the outcomes: time to death, all-cause mortality. |
| Selection of the reported results |
Moderate |
Comment: The outcomes and analyses are clearly defined in the Methods section. There is no prospectively registered protocol available. The study was not prospectively registered. Risk assessed to be moderate for the outcomes: time to death, all-cause mortality. |