PB1249 - Exploring the role of annexin A2 in the variation in bleeding phenotypes in persons with haemophilia A

Background: Some heterogenicity is believed to exist in the pattern of bleeding observed in persons with haemophilia A (PWHA) with similar residual FVIII levels. This suggests that other components of the clotting cascade such as the fibrinolytic system may contribute to the varied pattern of bleeding.

Aims: To measure the plasma levels of Annexin A2 and investigate its contribution to the varied bleeding tendencies in PWHA.

Methods: This was a single center cross-sectional analytical study involving 82 participants (42 PWHA and 40 age and sex-matched healthy controls). Age at first joint bleed and number of target joints were used to subdivide the patient group into; less severe (target joints of 0–1, and age at first joint bleed of >24 months) and more severe bleeding phenotype (target joints ≥2, and age at first joint bleed of ≤24 months) consisting of 22 and 20 patients respectively. Haematological parameters and plasma Annexin A2 concentration were measured using an ELISA kit (Elabscience Biotechnology Inc. USA). Ethical approval was obtained, and all participants provided written, informed consent before enrollment.
Statistical analyses were performed with SPSS version 24.0 for windows. A 2-tailed P value < 0.05 was considered significant.

Results: The mean plasma levels of Annexin A2 did not differ significantly between the patients and control groups (5.8 ± 2.7 vs. 5.9 ± 3.0) ng/mL. Plasma Annexin A2 levels also did not differ significantly between the severity groups (6.6 ± 2.7 vs. 5.1 ± 2.6) ng/mL. There was a weak negative correlation between Annexin A2 and age at first joint bleed (r = -0.362, p = 0.019).

Conclusion(s): Plasma Annexin A2 levels did not differ significantly between the two major groups and sub-groups. The negative correlation with age at first joint bleed may prompt further investigation of the fibrinolytic system.