Minimal factor XIII activity level to prevent major spontaneous bleeds.

Essentials A strong association between bleeding severity and FXIII activity level (FXIII:C) was shown. The range 5-30 IU dL-1 of FXIII:C was associated with a high variability of bleeding severity. The PROspective study confirmed the association between FXIII:C activity and bleeding severity.

A FXIII: C of 15 IU dL-1 is a proposed target to start prophylaxis for prevention of major bleeding.

SUMMARY: Background Congenital factor XIII (FXIII) deficiency is a rare bleeding disorder associated with significant bleeding manifestations. The European Network of Rare Bleeding Disorders (EN-RBD) study, performed from 2007 to 2010, showed a strong association between bleeding severity and FXIII activity in plasma of patients with FXIII deficiency. Among these patients, variable levels of FXIII activity, from undetectable to 30%, were associated with a wide range of bleeding severity. Objectives and patients The present cross-sectional study, in the frame of the PRO-RBDD project, a prospective cohort study, analyzed data of 64 patients with FXIII deficiency and different types of clinical and laboratory severity. Results The results of this analysis confirmed that FXIII coagulant activity in plasma is well associated with clinical severity of patients. In addition, 15 IU dL-1 of FXIII activity was identified to be the level under which the probability of spontaneous major bleeding sharply increases (from 50% for levels of 15 IU dL-1 to more than 90% for levels of 5 IU dL-1 or lower). Conclusion The PRO-RBDD study suggests a FXIII coagulant activity level of 15 IU dL-1 as a target to start prophylaxis in order to prevent major bleedings, such as central nervous system or gastrointestinal tract hemorrhages.