PROGNOSTIC VALUE OF PLATELET INDICES IN PATIENTS WITH PRIMARY IMMUNE THROMBOCYTOPENIA

Abstract

SUMMARY AND CONCLUSION I mmune thrombocytopenic purpura is an acquired immune-mediated disorder characterized by isolated thrombocytopenia, with the absence of any obvious initiating and/or underlying cause of the thrombocytopenia. There is no “gold standard” test that can reliably establish the diagnosis of primary ITP. Therefore, the diagnosis is one of exclusion and is based principally on patient history, physical examination, complete blood count, and review of the peripheral blood smear. Platelet indices are biomarkers of platelet activation. They allow extensive clinical investigations focusing on the diagnostic and prognostic values in a variety of settings without bringing extra costs. Among these platelet indices, mean platelet volume (MPV), platelet distribution width (PDW) and plateletcrit (PCT) were investigated. The aim of this study was to evaluate the correlation between pre- and post-treatment platelet indices values in ITP patients. The sensitivity and specificity of platelet indices for assessment of their predictive value at time of presentation for response to treatment were also evaluated aiming to settle a cut off value for MPV, PDW and PCT. This study was conducted on fifty newly diagnosed patients with primary ITP, classified as follows: Group I included twenty-five pediatric patients. Group II included twenty-five adult patients. Patients were selected from the Hematology Clinics of Ain Shams University Hospitals. In pediatric patients post treatment MPV and PDW were significantly decreased while PCT was increased when compared to their values at the time of presentation. The same results were obtained when studying adult patients group, except for PDW which did not attain any significance. A significant correlation was found between the pre-treatment values of the three platelet indices MPV, PDW and PCT and treatment response in pediatric patients, while no significant correlation was found between pre-treatment PDW values only and response to treatment in adult patients. The best cut off value of pre-treatment platelet count that was obtained for predicting the patients' response to treatment was >12 x 109/L with a diagnostic sensitivity 47%, specificity 100%, NPV was 26 % and PPV was 100%, While that of MPV was > 8.4 fL, with a diagnostic sensitivity 92.8% and specificity 87.5%. While the best cut off level for PDW was >15 fl. with a diagnostic sensitivity 78.5 % and specificity 87.5%. The negative predictive value was 43.8% and positive predictive value was 97.1%. The best cut off value of PCT for predicting treatment response was > 0.01, with a diagnostic sensitivity 57% and specificity 100%. Thus, our study concludes that increased pre-treatment MPV and PDW, together with decreased PCT can provide a significant diagnostic and reliable predictive value for treatment response in patients with primary ITP. From this study, we could conclude that: - Measuring of pre-treatment platelet indices (MPV and PCT) provides useful prognostic indicator of the response to treatment in primary ITP patients. - MPV and PDW are increased at the time of diagnosis of ITP and they decrease after establishing therapy and normalize after achieving complete response. - PDW cannot be considered one of the prognostic indicators in primary ITP adult patients.