Garg S, et al. - A systematic review and meta-analysis were conducted to examine the correlation between hydroxychloroquine (HCQ) levels and nonadherence, and SLEDAI scores, in SLE. A comprehensive search was performed. Researchers enrolled in observational and interventional studies that assessed HCQ levels and evaluated adherence or SLEDAI in adults with SLE. Seventeen were reviewed among 604 studies screened. In patients with low HCQ levels, they obtained 3 times higher odds of reported nonadherence. In the group with below threshold HCQ levels, the mean SLEDAI score was 3.14 points higher on a priori analysis, and 1.4 points higher in a group with HCQ levels below 500 ng/ml. It was noted that those with HCQ levels ≥ 750 ng/ml had a 58% lower risk of active disease, and their SLEDAI score was 3.2 points lower among 1,223 patients. A good correlation was observed between low HCQ levels and reported nonadherence. The evidence showed that HCQ levels of ≥ 750 ng/mL might be a potential therapeutic target.