PF328 PREDICTORS OF TREATMENT RESPONSE TO IMMUNOSUPPRESSANTS IN ACQUIRED HEMOPHILIA A

Background: Acquired hemophilia A (AHA) is a rare bleeding disorder, caused by inhibitors against factor VIII, which may result in life‐threatening bleeding. Management of AHA is two pronged ‐ to arrest bleeding with hemostatic agent and to eradicate FVIII inhibitors by immunosuppressants. However, immunosuppressants are associated with frequent adverse events, with infection being the leading cause of morbidity and mortality. Identifying predictors of treatment response may help tailor treatment strategies and reduce treatment associated adverse events. Aims: The aims of the study were to evaluate the presenting features, treatment, and outcomes of patients with AHA in our local population, to identify the predictors of normalization of aPTT after immunosuppressive therapy and overall survival; and to investigate the patient characteristics that predict normalization of aPTT by steroid alone within 6 weeks. Methods: This was a retrospective multi‐center study which recruited 108 patients diagnosed with AHA between 1 st January 2002 and 31 st December 2016. AHA is defined by the presence of a neutralizing FVIII inhibitor ≥ 0.6 Bethesda units (BU)/ml and a FVIII activity <50%. Patients with congenital hemophilia A with inhibitors were excluded. Prognostic factors for normalization of aPTT and overall survival were analyzed using Cox proportional hazards regression analysis. Results: Normalization of aPTT was an independent predictor of overall survival (OR 0.14, 95% CI 0.07–0.27, P  < 0.001). Patients with ECOG performance status ≤2 were more likely to attain normal aPTT (HR 2.09, 95% CI 1.28–3.42, P 0.003) while patients with underlying autoimmune diseases were less likely to achieve normal aPTT (HR 0.46, 95% CI 0.23–0.91, P 0.027). Female (OR 3.73, CI 1.15–12.2, P 0.028) and an inhibitor titer ≤20 BU/ml (OR 4.3, CI 1.36–13.63, P 0.013) predicted a higher chance of normalization of aPTT with steroid alone within 6 weeks. Summary/Conclusion: Identification of patients who are more likely to respond to steroid alone within 6 weeks may avoid unnecessary immunosuppressants and thus reduce treatment‐related adverse events. This finding may help individualize treatment strategies. Normalization of aPTT was an independent prognostic factor of survival. This finding echoed other studies and reiterated the importance of achieving remission. To date, the optimal immunosuppressive strategy remains elusive. Further high‐quality evidence is needed to guide the choice and intensity of treatment.