Hypothesis
Corticosteroid treatment during hospital stay would change in-hospital mortality among COVID-19 patients.
What failed
In a single-hospital cohort of 1,444 RT-PCR-confirmed patients, 559 received corticosteroids. Crude mortality was higher in the treated group (30.6% vs 21.7%), but after overlap-weight propensity balancing there was no association with in-hospital death (adjusted p = 0.25).
Broken assumption
Corticosteroid exposure changes the chance of dying in hospital with COVID-19.
Why
Once confounders were balanced the mortality difference disappeared; the only adjusted benefit the authors found was a lower risk of ICU admission. It is an observational cohort, not a trial.
From the published paper: Albani et al. Scientific Reports, 2021. ↗CC BY