Characteristics and Treatment Patterns of Patients with Haemophilia B Receiving Recombinant Coagulation Factor IX

<b>Introduction:</b> In Haemophilia B, guideline-level factor IX (FIX) prophylaxis is recommended, but real-world dosing and adherence vary. <b>Aim:</b> To assess treatment patterns, adherence, FIX dosing, and their associations with bleeding events in Korean patients. <b>Methods:</b> We conducted a retrospective chart review and one-time survey of 130 Korean patients with haemophilia B treated with FIX for ≥12 months at 12 centers (June 2022-May 2023). A total of forty-seven patients (36.2%) received prophylaxis (≥90 IU/kg/week for ≥45 weeks); the remainder were managed non-prophylactically. Annualized bleeding events (ABEs) were analyzed using negative binomial regression, and monthly bleeds with a generalized linear mixed model. Covariates with <i>p</i> < 0.10 and clinical relevance were included in multivariable models. <b>Results:</b> The prophylaxis group showed significantly fewer ABEs (incidence rate ratio [IRR]: 0.383, <i>p</i> = 0.011). Each 100 IU/kg monthly dose increment reduced bleed risk (IRR: 0.692, <i>p</i> < 0.001). Adherence showed no independent association with bleeding in adjusted models. <b>Conclusions:</b> Bleed prevention in haemophilia B is driven more by delivered FIX exposure than by regimen label. Study-defined sustained prophylaxis remains underused and under-dosed. Individualized dosing and continuous adherence monitoring are essential to close this treatment gap and improve outcomes.