An observational study to identify causative factors for non-use of hydroxychloroquine in systemic lupus erythematosus

Introduction: Hydroxychloroquine (HCQ) use is indicated for patients with systemic lupus erythematosus (SLE). However, HCQ was unavailable in Japan until 2015, and its usage is limited. Nevertheless, few reports are available discussing the reasons for not prescribing HCQ. Therefore, we aimed to identify the factors that interfere with HCQ use in patients with SLE. Method: This observational, single-center study included data from 265 patients with SLE in 2019. The patients were categorized into two groups: groups with and without a history of HCQ use. Between these groups, clinical characteristics, including demographics, disease duration, clinical manifestations, disease activity, treatment patterns, and laboratory data, were compared using univariate analysis and logistic regression models. Results: Among the 265 patients, 133 (50.2%) had a history of HCQ use. Univariate analysis identified the following variables related to HCQ non-use: older age, longer disease duration, lower prednisolone dose, lower SLE disease activity index 2000, lower estimated glomerular filtration rate, higher C3 level, and lower anti-double-stranded DNA antibody concentration. Logistic regression models identified a positive association between HCQ non-use and longer disease duration (odds ratio [OR]: 1.08), prednisolone dose ≤7.5 mg/day (OR: 4.18), C3 level ≥73 mg/dL (OR: 2.40), and attending physician having graduated >10 years prior (OR: 3.29). Conclusions: A longer disease duration, lower prednisolone dose, higher C3 level, and longer time since the graduation of attending physicians were associated with HCQ non-use. Therefore, physicians and patients should be educated to facilitate HCQ use despite these factors.