Delayed global standardization and prefectural disparities in systemic lupus erythematosus treatment in Japan: A nationwide study using the National Database of Health Insurance Claims and Specific Health Checkups of Japan

Objectives The aim of this study was to evaluate the status of the global standardization of, and prefectural differences in, systemic lupus erythematosus (SLE) treatments in Japan. Methods The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB Japan) was used. A patient with SLE was defined as having a disease with ICD-10 code M321 or M329 between April 2019 and March 2020, for which oral corticosteroids, immunosuppressive agents, or biologic agents were prescribed at least once during a given month. SLE treatments were evaluated by treatment centre type and prefecture. Results In total, 74,277 patients met the definition of SLE. The SLE prevalence was 60 per 100,000 (range: 47-102 per 100,000 by prefecture). Nationwide, 79.4% of the patients (range: 52.1-93.3% by prefecture) visited a specialized treatment centre (STC); 37.4% (range: 26.4-51.3% by prefecture) received only oral corticosteroids, with fewer of these patients visiting an STC than a non-STC (34.8% and 49.7%, P < .001); and 21.4% (range: 10.7-35.0%) received hydroxychloroquine, with more of these patients visiting an STC than a non-STC (23.0% and 13.5%; P < .001). Conclusions The NDB Japan demonstrated the delayed global standardization of, and prefectural disparity in, SLE treatments in Japan.