AB1190 DIRECT MEDICAL COSTS OF HOSPITALIZATION DURING THE MAINTENANCE THERAPY IN PATIENTS WITH ANTINEUTROPHIL CYTOPLASMIC ANTIBODY-ASSOCIATED VASCULITIS USING JAPANESE HEALTH INSURANCE DATABASE

Abstract

Background:Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) requires a long-term maintenance therapy (MT), often accompanied by hospitalization due to relapse and/or comorbidities such as infection1. However, data about direct medical costs of hospitalization during MT in patients with AAV is limited to date despite of an increasing concern about the economic burden of patients with AAV2-3.Objectives:To describe frequency of hospitalization and its direct medical costs during MT after the remission-induction therapy (RT) in patients with AAV using Japanese health insurance database.Methods:This retrospective longitudinal population-based study was conducted using claims data in Japan provided by Medical Data Vision Co., Ltd. We defined individuals as AAV cases receiving RT if they met all of the following: 1) having at least one ICD10 code (M300, M301, M313, or M318); 2) having at least one prescription of oral corticosteroids with prednisolone-equivalent dosage ≥30 mg/day, methylprednisolone pulse therapy, immunosuppressive drugs (cyclophosphamide [IVCY], methotrexate, or mycophenolate mofetil), or rituximab (RTX) during hospitalization between April 2008 and April 2017; and 3) having at least 7 days of hospitalization. The observation started from the next day of discharge from the first hospitalization for RT and ended at 24 months later, the month of loss of follow-up, or April 2017. We described the frequency of hospitalization and calculated direct medical costs (per month) during the observation. We analyzed medical costs from a societal perspective. We classified reasons of hospitalization into 3 categories; intensification of treatments for AAV, AAV MT including IVCY or RTX treatments, and comorbidities (infection, cardiovascular disease [CVD], malignancy, and others) using ICD10 codes plus treatments or interventions during the hospitalization.Results:In this study, 1,703 patients with AAV were included. The median [IQR] age was 72 [63, 79] years and 55.7% were female. The total number of hospitalization was 1,897 in 863 patients (50.7%). Among the hospitalizations, 296 hospitalization in 235 patients were categorized as intensification of treatments for AAV, 627 hospitalization in 297 patients were AAV MT, and 974 hospitalization in 572 patients were categorized as comorbidities. In the last category, infections were most frequent (220), followed by malignancy (54) and CVD (15). The mean direct medical costs per month was 20,945 EUR (1 EUR=125 JPY) in patients with hospitalization and 599 EUR in those without. Patients with hospitalization due to intensification of treatments for AAV had the highest direct medical costs (3,000 EUR), followed by those with hospitalization due to comorbidities (2,001 EUR), and those with hospitalization due to AAV MT (1,649 EUR).Conclusion:More than half of the patients had hospitalization during MT, and hospitalization due to comorbidities were most frequent. The mean direct medical costs in patients with at least one hospitalization was approximately 3.5 times as high as that in those without hospitalization.