(HealthDay)—Hydroxychloroquine (HCQ) blood levels are useful in predicting retinopathy among patients with systemic lupus erythematosus (SLE), according to a study published online Sept. 18 in Arthritis & Rheumatology. Michelle Petri, M.D., from the Johns Hopkins University School of Medicine in Baltimore, and colleagues assessed the risk for HCQ retinopathy by clinical characteristics and levels of...