Trends in mortality and morbidity in patients with bullous pemphigoid before and after approval of intravenous immunoglobulin in Japan: an interrupted time-series analysis

Abstract

Abstract Background Intravenous immunoglobulin (IVIg) has been reported to be an effective treatment for bullous pemphigoid. However, the impact of IVIg approval on real-world outcomes remains unclear. Objectives To investigate the effect of IVIg approval on patients with bullous pemphigoid using a national inpatient database. Methods Using the Japanese Diagnosis Procedure Combination database, we identified 14 229 patients admitted to hospital for bullous pemphigoid and treated with systemic corticosteroids between July 2010 and March 2020. We conducted an interrupted time-series analysis to compare in-hospital mortality and morbidity between the patients admitted before and after the approval of reimbursement of IVIg for bullous pemphigoid in the Japanese universal health insurance system in November 2015. Results In-hospital mortality was 5.5% before and 4.5% after the approval of IVIg reimbursement. After the IVIg approval, 18% of the patients were treated with IVIg. Based on the interrupted time-series analysis, in-hospital mortality significantly decreased at the time of approval [–1.2%, 95% confidence interval (CI) –2.0 to –0.3, P = 0.009] and a downward trend was observed after the approval (–0.4% annual rate, 95% CI –0.7 to –0.1, P = 0.005). In-hospital morbidity also demonstrated a downward trend after the approval. Conclusions IVIg approval is associated with lower in-hospital mortality and morbidity in inpatients with bullous pemphigoid.