Poor Platelet Function on Sonoclot Signature Is Associated with High Incidence of Bleeding in Severe Immune Thrombocytopenia

Introduction: Patients of immune thrombocytopenia (ITP) are at an high risk of bleeding, and the risk of bleeding is maximum when platelet counts fall below 30,000/μL (severe ITP). Though it is not known not all patients have a similar risk of bleeding at a given platelet count. In 59th ASH annual meeting, 2017 (poster 2320) Mishra K et al showed that the platelet function measured by 'Sonoclot coagulation and platelet function analyzer' is significantly different in bleeders as compared to non-bleeders severe ITP patients. We aimed to investigate and follow up the non-bleeder severe ITP patients, whose platelet count remains <30,000 with or without treatment, and find out the incidence of bleed.

Method: The study was conducted at the department of internal medicine, postgraduate institute of medical education and research, Chandigarh, India. In this prospective observational study, severe ITP (newly diagnosed) and without active bleeding (WHO bleeding grade <2) were included. All these patient were clinically evaluated, and blood samples were collected as per unit protocol for ITP including Sonoclot analysis. For Sonoclot analysis, fresh blood samples were drawn in citrated vacutainer and analyzed by Sonoclot coagulation and platelet function analyzer made by Sienco, Inc, model SCP1 (USA). The sonoclot signature assessment gives activated clotting time (ACT), clot rate (R1) and platelet function (PF). The samples for sonoclot analysis were monthly drawn for six months in patients who continued to have severe ITP.

Results: A total of 50 patients with severe ITP were included. Twenty patients were not included in the final analysis as their platelet remained above 30,000/μL during follow up. The remaining 30 patients were divided into two groups based on normal platelet function (PF) (>1.5) and low PF (<1.5) as measured by the Sonoclot analyzer. The normal PF group (n= 17) had only one patient who had clinically significant bleeding (WHO grade > 2), while low PF group had four patients with clinically significant bleeding (Figure 1). Though the statistical significance level could not be achieved, likely due to a small cohort of patients, the results look promising and shows the potential of sonoclot to give valuable input regarding the risk of bleeding in severe ITP.

Conclusion: The patients with poor platelet function as measured by 'Sonoclot coagulation and platelet function analyzer' had more bleeding episodes as compared to patients with normal platelet function. Therefore, Sonoclot may work as a point of care investigation to predict the risk of bleeding in severe ITP patients. This will help the clinician in being more conservative in the management of severe ITP patients with low risk of bleeding and avoid unnecessary therapy. We conclude that the use of Sonoclot during follow-up in severe ITP patients has prognostic significance.

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