Comparison of CQ/HCQ users with the general population in a region of Italy, showing no significant difference in the probability of COVID-19.
CQ/HCQ users were mostly systemic autoimmune disease patients and authors do not adjust for the very different baseline risk for these patients. Other research shows that the risk of COVID-19 for systemic autoimmune disease patients is much higher overall, Ferri et al. show OR 4.42, p
Salvarani et al., 8/6/2020, retrospective, population-based cohort, Italy, Europe, peer-reviewed, 18 authors.
risk of COVID-19 case, 6.0% lower, RR 0.94, p = 0.75.
Effect extraction follows pre-specified rules
prioritizing more serious outcomes. For an individual study the most serious
outcome may have a smaller number of events and lower statistical signficance,
however this provides the strongest evidence for the most serious outcomes
when combining the results of many trials.