Among patients with severe hemophilia A, lower levels of platelet surface phosphatidylserine are linked with bleeding risk, according to research published in the Journal of Thrombosis and Haemostasis.

Hemophilia A, which is characterized by severe factor VIII deficiency, leads to highly variable bleeding events, regardless of whether factor VIII prophylaxis is used. Although factor VIII activity explains 70% of the variance in bleeding events among patients, 30% of the variance remains unexplained.

Variance in platelet physiology has also been linked with bleeding events in this patient population, although these findings have not yet been confirmed. For this study, researchers evaluated whether, among patients with severe factor VIII deficiency receiving prophylaxis, platelet function is linked with or predictive of bleeding events.

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Overall, data from 34 patients were included in this study. The median age was 12.6 years (range, 2.6-21.6), all patients had a baseline factor VIII activity of less than 1 IU/dL, and the mean prescribed prophylactic dose was 26.2 IU/kg. The majority (23; 68%) of patients had a prescribed infusion frequency of every 48 hours.

Analysis suggested that lower levels of platelet surface phosphatidylserine expression, which was measures by annexin V binding to platelets, were directly linked with prior and future bleeding events at baseline. Phosphatidylserine expression was linked with bleeding in any location and with hemarthrosis.

No other platelet activity markers were predictive of bleeding events.

“Although prophylaxis has dramatically reduced debilitating hemarthropathy, bleeding events still occur and threaten longitudinal joint health and productivity,” the authors wrote. “A larger, multicenter study is needed to confirm the clinical utility of platelet surface phosphatidylserine as a biomarker for future bleeding risk in this population, as well as for those with mild/moderate FVIII deficiency and more severe bleeding phenotypes and for those patients now on emicizumab for prophylaxis.”

Disclosures: Some authors have declared affiliations with or received funding from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


Croteau SE, Frelinger AL 3rd, Gerrits AJ, Michelson AD. Decreased platelet surface phosphatidylserine predicts increased bleeding in patients with severe factor VIII deficiency. J Thromb Haemost. Published online December 28, 2020. doi:10.1111/jth.15223