Despite the small number of published studies, some governments have recommended using HCQ as prophylaxis for healthcare workers, and some prominent political figures have asserted that CQ or HCQ should be used as a first‐line treatment for COVID‐19. Sadly, there have already been instances of significant harm where individuals have misinterpreted news stories about the use of CQ and suffered toxicity as a result.
More recently, a number of larger non‐randomized studies have reported beneficial effects of HCQ. A retrospective cohort study in Michigan, USA compared four groups of a total of 2541 patients hospitalized with confirmed COVID‐19 according to physician‐directed treatment assignment: 1202 received HCQ; 147 azithromycin alone; 783 HCQ with azithromycin; and 409 received neither drug (
Arshad 2020). A significant reduction in mortality was reported when HCQ was received (hazard ratio (HR) 0.49, 95% confidence interval (CI) 0.29 to 0.83). Differences in baseline characteristics suggested underlying confounding, although an underpowered propensity‐matching analysis reported persistence of the reported mortality benefit (
Arshad 2020). The quantity of missing data and early patient exclusions were not reported (
Arshad 2020). Another study retrospectively comparing 4542 patients in Belgian hospitals reported lower risk of death in the group who received HCQ as per national guidance (804/4542, 17.7%) versus 3533 patients who did not receive HCQ (957/3533, 27.1%) (
Catteau 2020). After adjusting for multiple covariates, this difference was found to be statistically significant (adjusted HR 0.68, 95% CI 0.62 to 0.76) (
Catteau 2020). Of note, nearly 50% of patients screened for eligibility were excluded, though some of these patients were found to have similar baseline characteristics to those included in the analysis (
Catteau 2020).
At the time of writing the protocol for this review, China had reported two small randomized trials of HCQ, with mixed results (
Chen 2020a;
Chen 2020b). Several trials have since been reported and are included in this review.
