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

Objectives: To evaluate the status of the global standardization of, and prefectural differences in, systematic lupus erythematosus (SLE) treatments in Japan.

Methods: The Japanese National Database of Health Insurance Claims and Specific Health Checkups (NDB Japan) was used. A patient with SLE was defined as having a disease with ICD10 code M321 or M329 between April 2019 and March 2020, for which oral corticosteroids (OCS), immunosuppressive agents or biologic agents were prescribed at least once during a given month. SLE treatments were evaluated by treatment center 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 center (STC); 37.4% (range: 26.4% - 51.3% by prefecture) received only OCS, with fewer of these patients visiting a STC than a non-STC (34.8% and 49.7%, p<0.001); and 21.4% (range: 10.7% - 35.0%) received HCQ, with more of these patients visiting a STC than a non-STC (23.0% and 13.5%; p<0.001).

Conclusions: NDB Japan demonstrated delayed global standardization of, and prefectural disparity in, SLE treatments in Japan.