Evaluation of Thrombin Generation Assay in Patients with Hemophilia

Background: Diagnosis of hemophilia is based on detection of factor level and coagulation screening test. These screening tests can not reflect global hemostatic balance. Thrombin generation (TG), as a focal point and key process, is an important step in hemostasis and thrombosis. Recent evidence has indicated that TG assay is a better predictor of the coagulation capacity and subsequently overall assessment of hemostasis compared with traditional coagulation tests. The parameters of the thrombogram are helpful in the evaluation of bleeding or thrombotic risk and also in the management of these situations.

Objective: The aim of this study is to evaluate the correlation between TG parameters with bleeding symptoms and disease severity in patients with hemophilia.

Methods: In this cross-sectional study, 59 male patients with hemophilia were randomly selected from those already registered at Shiraz Hemophilia Center of southern Iran, from February to December 2012. Also, 38 healthy age-matched men were considered as a control group from those referred for check up. Informed written consent was obtained from all participants. The proposal was approved by the Medical Ethics Committee of Shiraz University of Medical Sciences. Disease severity was defined based on the activity level of deficient factor (severe <1%, moderate from 1 to 5%, and mild >5% IU/dL). Bleeding score (BS) was calculated by performing a clinical evaluation using a modified questionnaire based on Tosetto et al- questionnaire. Correlation of TG parameters with disease severity and BS were determined.

Results: From 59 patients with hemophilia (52 hemophilia A and 7 hemophilia B), 40 patients (68%) had severe disease, 14 (24%) moderate and 5 (8%) mild disease. All TG parameters showed statistically significant differences between patients and controls (P<0.001). Only Lag time showed a statistically significant correlation with BS (r_s= 0.316, P =0.016). All TG parameters except peak showed association with disease severity (P<0.05). In addition, endogenous thrombin potential showed a significant correlation with factor activity level (r_s= 0.459, P <0.001). Both Lag time and start tail showed significant negative correlations with factor activity level (r_s= -0.488, P <0.001 and r_s=- 0.289, P <0.026 respectively).

Conclusion: Based on our results, although most of the TG parameters evaluated were not significantly correlated with bleeding score of hemophilia patients, the majority of TG parameters were significantly associated with factor activity level and disease severity. In patients with hemophilia, plasma factor activity level has a poor predictive value in the evaluation of efficacy of treatment; but it seems that TG assay is an appropriate tool for assessment of global hemostasis and better reflection of clotting function in the management of patients with hemophilia.