Retrospective cohort analysis of treatment patterns and bleeding outcomes in the Korean bleeding disorder registry (KBDR)

Abstract Background Hemophilia is a rare congenital bleeding disorder characterized by the deficiency of clotting factors, which can lead to spontaneous bleeding and joint damage if left untreated. Understanding the real-world epidemiology and treatment patterns of hemophilia requires robust longitudinal data, especially in countries where such data have been limited. In response to this need, the Korean Bleeding Disorder Registry (KBDR) was established as the first comprehensive, nationwide registry for hemophilia and other bleeding disorders in Korea. This study presents the results from a retrospective cohort analysis derived from the KBDR, focusing on treatment patterns, prophylaxis utilization, bleeding events, and factor usage. Methods The KBDR was developed using iCReaT (Internet-based Clinical Research and Trial Management System), a government-supported clinical research infrastructure operated by the Korea National Institute of Health. The registry is designed as a hybrid retrospective and prospective observational platform. Seven major hemophilia treatment centers across Korea initially participated in data collection, with ongoing expansion to additional centers nationwide. All participating centers obtained Institutional Review Board (IRB) approval for registry participation and data sharing. From the registry population, we extracted retrospective clinical records between 2021 and 2023. Collected data included demographic characteristics, hemophilia type and severity, treatment modality (prophylaxis vs. on-demand), prescribed clotting factor regimens, and annualized bleeding rates (ABR), with a focus on joint and severe hemorrhages. Data were analyzed descriptively and stratified by disease severity and age group. Results As of 2023, a total of 2,908 unique patients had been registered in the KBDR: 2,028 with hemophilia A, 507 with hemophilia B, and 52 with hemophilia C. Among these, 1,423 patients had complete retrospective clinical records available for analysis: 1,088 with hemophilia A, 220 with hemophilia B, and 11 with hemophilia C. Among patients with hemophilia A, 72.1% received prophylactic treatment, while 70.0% of those with hemophilia B and 50.0% of those with factor VII deficiency were on prophylaxis. In patients with severe hemophilia A, the prophylaxis rate was 79.0%; in moderate hemophilia A, it was 62.8%. Among those with severe hemophilia B, 80.8% received prophylaxis compared to 56.6% in moderate cases. When stratified by age, 83.7% of patients under 20 years with severe hemophilia received prophylaxis, followed by 80.9% in the 20–40 age group. In hemophilia B, the highest prophylaxis rate (83.3%) was observed in the 20–40 age group, followed by 76.9% in those under 20. For those receiving standard half-life (SHL) factor VIII, the median annual number of infusions was 61.6, whereas patients receiving extended half-life (EHL) factor VIII had a median of 56 infusions per year. For factor IX, the median annual number of infusions was 51.9 for SHL and 11.9 for EHL. A total of 31 patients received emicizumab, with a median of 10.7 administrations annually. Joint bleeding outcomes were favorable: in patients with severe hemophilia A, the median number of annual joint bleeds was 0 (IQR: 0–10), with a mean of 13.6. In severe hemophilia B, the median was also 0 (IQR: 0–11.1), with a mean of 13.7. These findings suggest a relatively low frequency of joint bleeding among patients on prophylactic regimens. Conclusion The KBDR has enabled the first large-scale retrospective analysis of hemophilia treatment patterns in Korea. The data demonstrate a high rate of prophylaxis use, particularly in younger and more severely affected patients, and favorable bleeding control across the cohort. As the registry moves into its prospective phase, it is expected to provide further insights into long-term outcomes, optimize individualized treatment strategies, and ultimately improve the quality of life and clinical outcomes for people living with hemophilia in Korea.