Baseline VWF:Ag Level and Body Mass Index Are Inverse Influencing Factors of Annualized Total Bleeding Rate and Annualized Joint Bleeding Rate Respectively in Severe-Type Adult Patients with Hemophilia a (PwHA) with Episodic Treatment with rFVIII

Introduction: Bleeding phenotypes of severe-type patients with hemophilia A (PwHA) vary greatly, which influence factor consumption and medical cost. Factors affecting bleeding patterns of PwHA include various procoagulant and anticoagulant factors, joint condition and physical activity, etc. We aimed to investigate clinical factors influencing by-nature bleeding frequency of severe-type PwHA during episodic treatment.

Methods and materials: There were 19 non-inhibitor, severe-type, previously treated PwHA aged >20 years, who had at least one to five major joints arthropathy, retrospectively enrolled from two hemophilia centers for analysis. They had been refusing prophylaxis therapy with FVIII product due to heavy burden of frequent intravenous FVIII injection and had long-term episodic treatment. Clinical informations were collected from November 2017 to November 2018, including age, body mass index (BMI), body weight, ABO blood grouping, HCV and HIV infection status, baseline VWF:Ag and VWF:activity, mutation of F8 gene. Annualized bleeding rate (ABR) and annualized joint bleeding rate (AJBR), weekly doses and annualized factor consumption costs (calculated by new Taiwan dollars, NTD) were obtained from the patients' medical records.

Results: The PwHA with ABR <24 had significantly lower proportion of blood-group-O patients, higher baseline VWF:Ag and VWF:activity than those with ABR >24.(P-value <0.05) The PwHA with AJBR <13 had significantly higher BMI than those with AJBR >13.(P-value <0.05) There was no significant difference in ABR, AJBR, weekly dose, and annualized factor cost between PwHA with O blood group and non-O blood group. Compared with PwHA with baseline VWF:Ag or VWF:activity <145%, those with baseline VWF:Ag or VWF:activity >145% had significantly older age (34.9 vs 53.2 years, P-value <0.05), higher BMI (25.2 vs 29.9, P-value <0.05), lower ABR (58.2 vs 12.2 per year, P-value<0.01), lower AJBR (46.8 vs 10.8 per year, P-value<0.01), lower weekly dose (42.4 vs 10.6 IU/kg/wk, P-value<0.01), and lower annualized factor consumption costs (4,177,732 vs 1,120,704 NTD, P-value<0.01). Compared with PwHA with BMI <28, those with BMI >28 had significantly lower ABR (58.2 vs 12.2 per year, P-value<0.05), lower AJBR (46.8 vs 10.8 per year, P-value<0.05), higher baseline VWF:activity (94.6% vs 190.2%, P-value <0.05), and lower weekly dose (38.5 vs 17.1 IU/kg/wk, P-value <0.05). By backward-stepwise multivariate linear regression, baseline VWF:Ag and BMI were identified as independent and significant inverse influencing factors for ABR and AJBR, respectively.(P-value <0.05)

Conclusion: For severe-type adult PwHA with episodic treatment, baseline VWF:Ag or VWF:activity >145% was associated with lower ABR, AJBR, weekly dose, and annualized factor cost. BMI >28 was associated with lower ABR, AJBR, and weekly dose consumption. Baseline VWF:Ag and BMI were revealed as inverse influencing factors for ABR and AJBR, respectively. The results of our study could be useful for clinicians to have an insight into diversity of bleeding phenotypes of by-nature severe-type PwHA. For developing countries where factor concentrate resources are not enough, these clinical influencing factors might be helpful for the management of therapeutic strategies and resource allocation for severe PwHA.