Magagnoli et al [59]. Retrospective study HCQ group:n = 97HCQ＋azithromycin: n = 113No HCQ group:n = 158 Not specified. The use of HCQ, either with or without azithromycin, didn’t reduce the risk of mechanical ventilation in patients hospitalized with COVID-19; Patients treated with HCQ alone was associated with increased overall mortality. The study data comes from a comprehensive electronic medical record; Strictly defined covariates and outcomes; Using propensity scores adjustment for a large number of relevant confounders to make results more persuasive. Retrospective nature of the study; The subjects included only men and most of them were black; Despite adjustments to many possible confounding factors, there may still be undiscovered factors.