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 24% lower mortality [19‑28%]
from meta analysis of the 237 mortality results to date
This study is excluded in the after exclusion results of meta
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
Vernaz et al., 31 Dec 2020, retrospective, propensity score matching, Switzerland, peer-reviewed, 15 authors.