Minimal factor XIII activity level to prevent major spontaneous bleeds.

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 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 to more than 90% for levels of 5 IU/dL or lower). CONCLUSION: the PRO-RBDD study suggests a FXIII coagulant activity level of 15 IU/dL as a target to start prophylaxis in order to prevent major bleedings, such as central nervous system or gastrointestinal tract hemorrhages.