email article Monitoring blood levels of hydroxychloroquine (HCQ) among patients with systemic lupus erythematosus (SLE) could help preserve the anti-thrombotic effects of the drug without increasing the risk for retinal toxicity, researchers reported. Rates of thrombosis declined by 13% for every increase of 200 ng/mL in overall mean blood levels of HCQ, for a rate ratio of 0.87 (95% CI 0.76-1, P=0.0559) after adjustment for age, ethnicity, hypertension, lupus anticoagulant, and levels of C3 complement. Significant reductions also were seen specifically for the most recent blood level measurement, with a rate ratio of 0.87 (95% CI 0.78-0.98, P=0.0249), said Michelle Petri, MD, and colleagues from Johns Hopkins University School of Medicine in Baltimore.