In children with BTM, significant hemostatic alterations, such as bleeding or thrombosis, have been identified [3–7]. These alterations have been linked to iron overload from repeated blood transfusions causing hepatic dysfunction [4, 7, 8]. Hepatic iron overload in BTM usually does not manifest as pronounced hepatic dysfunction until serum ferritin levels exceed 2,000 ng/mL [9]. In this study, the hemostatic status of transfusion-dependent BTM children with a history of bleeding or thromboembolic episodes was assessed using the Sonocolt analyzer and conventional tests.
In the current study, the percentage of subjects with thrombosis (4.9%) in our β-thalassemia patients is comparable to a study done by Borgna-Pignati et al. who observed TEE in 3.95% of their β-thalassemia major patients (n = 685, mean age = 16 years) [13]. The young age of this study’s population could explain the low percent of thrombotic complication identified among them. As children getting older, they are exposed to more risk factors that may reveal thrombotic events.
Moreover, the traditional coagulation parameters including PT, aPTT, Fibrinogen, and D-dimer showed no significant difference among the studded groups. Contrary, the CRs of the children in the thrombotic group were significantly higher compared to the uncomplicated and bleeders group. The conventional coagulation tests revealed no discernible differences between the groups under investigation. Sonoclot offers advantages over traditional laboratory testing, including higher sensitivity and real-time dynamic viscoelastic property of clot progression [12]. Valuation of prothrombotic states using sonoclot has been done in numerous earlierstudies. Francies et al. examined significantly elevated CR in cancer patients using the sonoclot analysis to determine their prothrombotic state.[14]
Saxena et al., studded the hemostasis in Patients with Liver Disease using the sonoclot analyzer and correlated the results with Conventional Coagulation tests. They recorded higher level of CRs in Cirrhotic patients compared to the control [15]. The underlying hypercoagulability in these patients may be better understood in light of these aberrant values of CR. As Saxena et al., explained hypercoagulability in cirrhosis could be attributed to decrease in the levels of natural anticoagulants [15], we reported statistically significant higher serum ferritin in children with thrombosis in comparison to other groups. similarly, in β-thalassemia patients with marked hyperferritinemia and subsequent hepatic dysfunction .
Although The hypercoagulable proclivity in thalassemia patients is not discernible from routine coagulation tests, because there are inadequate measuring tools to determine patients who are at risk to develop clots [16]. However, the abnormal high CR could identify the underlying prothrombotic tendencies in these patient.
Since the follow-up of these cases was not included in our study, it is not possible to conclusively demonstrate the predictive value of CR with respect to the prothrombotic tendency in these patients. However, there is a lot of potential to investigate this sonoclot parameter as a hypercoagulable state predictor in BTM.
The study showed statistically significant higher serum ferritin in patients with thrombosis in comparison to the non-complicated and bleeder groups which is consistent with study was done in Iraq [17]. Iron toxicity due to hemolysis lead to decline in the production of nitric oxide (NO) and endothelium damage and vasculopathy [18]. Also, free iron secondary to hemochromatosis lead to revelation the negatively charged phospholipids, mainly phosphatidylserine, at the outer membrane which provides a procoagulant surface for the activation of coagulation system and thrombin generation [19].
Platelet aggregation is a sensitive investigation of platelet function. In vitro platelet aggregation in response to agonists such as epinephrine, thrombin, collagen, and ristocetin can distinguish platelet function disorders. In the present study the platelet aggregation ADP, AA did not significantly differ from the uncomplicated group.
The Sonoclot analyzer measures platelet function by combining the peak amplitude and time to peak into a single parameter called platelet function. This parameter is rated 0–5, with 5 representing strong platelet function.[20]
In the current study, we found that platelet function via clot retraction was abnormal higher in thrombotic patients compared to all patients studied. This could be attributed to chronic activation of platelets either due to the reduced NO levels, which is a major guardian of endothelial integrity and smooth muscle tone regulator, promoting platelet activation and vasoconstriction [21], or due to the pro-coagulant RBC thalassemic membrane stimulating thrombin, which is a strong platelet agonist, that enhance platelet activation [22].
Conversely, patients exhibiting bleeding symptoms had statistically significant lower Sonoclot PF when compared to the non-complicated group. Nevertheless, they displayed non-significantly lower platelet aggregation with ADP and AA (43.4 ± 33.8 and 38.8 ± 35.3%, respectively), corresponds with the study by El-Beshlawy et al. [23]. Various reasons havebeen proposed for platelet hypoaggregation such as: increased levels of circulating antiplatelet antibodies in β-thalassemia patients and their suggested role in causing increased platelet disaggregation with resultant in vitro platelet hypoaggregation [24]. Also, chronic in vivo activation of platelets due to release of ADP from hemolyzed RBCs renders platelets refractory to further stimuli in vitro [25]. Lastly, Iron overload with subsequent non-transferrin-bound iron formation, has an oxidative stress that damage platelet membrane, resulting in defective platelet aggregation [26]. Our results didn’t show significant correlation between either CD62p with ADP and AA nor ferritin level with ADP and AA in a discordance with last 2 hypotheses.
Several studies comparing sonoclot PF with other laboratory methods for assessing platelet function. Michael et.al. evaluated the platelet function using Sonoclot (Sienco Inc.) and platelet aggregometry following the administration of therapeutically dosages of the glycoprotein IIb/IIIa antagonist tirofiban with or without heparin. They found that the glass bead-activated test from Sonoclot successfully detects glycoprotein IIb/IIIa receptor inhibition with tirofiban when compared to platelet aggregometry [27]. Moreover, Alok Kumar and his collogues compared the prognostic value of Sonoclot analysis and thromboelastography (TEG) for postoperative bleeding in children underwent cardiac surgery. they found that preoperative PF has the maximum predictive value to anticipate post-oprative bleeders among parameters derived from Sonoclot and TEG, and it may be used to predict postoperative bleeders [28].
Fayed and his colleges have identified significant difference in CD62p (P-selectin) expression as a marker of hypercoagulability in their β-thalassemia group rather than controls [29]. In parallel, we have compared CD62p expression in all study groups and found nonsignificant difference. However, P-selectin level is considered abnormally high in both bleeder and thrombotic groups (24.6 ± 25.4% vs. 20.2 ± 29.4%) respectively. Such relatively high levels of CD62p in both groups either questions the consistency of this marker in reflecting the status of hypercoagulability in those patients or it’s elevation in bleeder group suggests the complexity of the coagulation balance so that other factors; thrombocytopenia, platelet hypoaggregation or hypofibrinogenemia, has taken over this group’s towards bleeding rather than thrombosis.
In literature, thrombophilia in patients with β-thalassemia is explained by many factors such as endothelial cell stimulation, abnormal RBC membrane, and activation of platelets and coagulation system [30]. Furthermore, the enhanced thrombin generation activates platelets, monocytes, granulocytes, and endothelial cells, which further enhance the prothrombotic process [31]. As regard our study, hypercoagulability causes in β-thalassemia patients as extracted from our results are: hyperferritinemia, and platelet activation which is represented by high PF and CD62p. This hypercoagulable state could be reflected through high clot rate rather than D-dimer.
It is not very common for sonoclot values and traditional coagulation tests to correlate [32, 33]. To determine whether sonoclone can replace several coagulation tests in these patients, we have attempted to compare the sonoclot parameters with conventional testing in this study. While CR has shown a statistically significant negative correlation with PC and D-dimer, SON-ACT have demonstrated a statistically significant positive correlation with APTT, although most of patients are within normal range. Also, significant positive correlation between platelet function by Sonoclot with ADP & arachidonic acid by aggregometer. These results are consistent with prior research attempts to identify comparable associations [15, 34]. Once acquired, these sonoclot factors can then be utilized to forecast.
Conclusion; Sonoclot analysis may verify as an effective method for evaluating hemostatic abnormalities in children with BTM. Clot rate and PF may become a possible future predictors of hyper and hypo -coagulability respectively. Since conventional tests alone have demonstrated poor reproducibility with bleeding and thrombotic risks, the statistically significant correlations between routine tests and sonoclot parameters demonstrate that this traditional test of coagulation should be used in conjunction with the standard tests to define the hemostatic profile in BTM. Further large studies should purpose at developing transfusion protocols based on Sonoclot characteristics and using anticoagulants or even prophylactic medication for patients with thalassemia.