Publication Only: Thalassemias
Thalassemia is an inherited hemolytic anemia known to be associated with hypercoagulable state. Several factors including the abnormality of thalassemic red blood cell (RBC) membrane, increased platelet count, decreased anticoagulant proteins and increased circulating microparticles (MPs) contribute to the hypercoagulability in thalassemia. Global hemostatic changes as measured by rotatory thromboelastometry (ROTEM®) have been demonstrated in patients with beta-thalassemia/hemoglobin E disease (beta-thal/Hb E). However, there is little information in patients with hemoglobin H disease (Hb H) which is a less severe but highly prevalent non-transfusion dependent thalassemia.
To compare the global hemostatic changes and the levels of circulating MPs among children and adolescents with Hb H, beta-thal/Hb E and healthy controls.
A cross-sectional study was conducted in 38 subjects with Hb H, 22 subjects with beta-thal/Hb E and 12 healthy age-matched controls. Complete blood count, ROTEM® and quantitation of circulating MPs [annexin V + MPs, red blood cell (RBC) derived MPs (RMPs) and platelet derived MPs (PMPs)] as analyzed by flow cytometry were performed in all subjects.
The age (range 5-21 years) and percentage of male gender (range 50-58%) among the Hb H, beta-thal/Hb E and control groups were not statistically different (P = 0.383 and P = 0.798, respectively). The Hb levels were higher and the numbers of nucleated RBC (nRBC) were lower in the Hb H group than in beta-thal/Hb E group. Overall, the ROTEM® parameters were not statistically different among the thalassemia and control groups. However, within the thalassemia subjects group, the maximum clot firmness (MCF) in splenectomized patients was significantly higher than non-splenectomized subjects (P < 0.001). The levels of annexin V + MPs in both Hb H and beta-thal/Hb E groups were significantly higher than the control group (P = 0.001). RMPs in beta-thal/Hb E group were higher than the controls (P = 0.013) while there was no difference between the Hb H and control groups (P = 0.097). The level of circulating MPs was slightly higher in splenectomized subjects, but the differences were not statistically significant. Only the platelet count and nRBC, but not the circulating MPs, were significantly correlated with MCF in both INTEM (r = 0.620, P < 0.001 and r = 0.322, P = 0.006 respectively) and EXTEM (r = 0.567, P < 0.001 and r = 0.326, P = 0.005, respectively).
The global hemostasis parameters as measured by ROTEM® were not different among the Hb H, beta-thal/Hb E and control groups in this study. Hypercoagulable state was more commonly found in thalassemia subjects who were splenectomized, regardless of genotypes. The hypercoagulability was associated with higher nRBC and platelet count in the splenectomized group. Patients with Hb H had significantly higher circulating MPs levels than healthy controls although with the lesser extent than those seen in beta-thal/Hb E.