Retrospective 840 hospitalized patients in Switzerland showing non-statistically significant lower mortality with HCQ but significantly longer hospitalization times.
Confounding by indication is likely. PSM fails to adjust for severity with a 16% higher mNEWS score for HCQ vs. SOC in the matched cohort.
Time varying confounding is likely. HCQ became controversial and was suspended towards the end of the period studied, therefore HCQ use was likely more frequent toward the beginning of the study period, a time when overall treatment protocols were significantly worse.
Authors note: "overall, there was an indication bias, with the reason of prescription being associated with the outcome of interest. Indeed, patients with more severe COVID-19 were more likely to receive experimental therapies."
Although the 15% lower mortality is not statistically significant, it is consistent with the significant 25% lower mortality
[20‑29%] from meta analysis of the
247 mortality results to date.
This study is excluded in the after exclusion results of meta
analysis:
substantial
confounding by time likely due to declining usage over the early stages of the pandemic when overall treatment protocols improved dramatically; substantial unadjusted
confounding by indication likely.
Vernaz et al., 31 Dec 2020, retrospective, propensity score matching, Switzerland, peer-reviewed, 15 authors.
