Assessment of Immature Platelet Fraction in Pregnancy-Associated Thrombotic Microangiopathy

Abstract

Thrombotic microangiopathy (TMA) syndromes are extraordinarily diverse. Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are the two most well known, and are considered to be the most serious, TMA syndromes. TTP–HUS occurs more commonly in women and among women is commonly associated with pregnancy. Nevertheless, there are other pregnancy conditions that may manifest with TMA, including preeclampsia, eclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), in addition to acute fatty liver of pregnancy, antiphospholipid syndrome, and systemic lupus erythematosis. Assessment of immature platelets was introduced as a non-invasive test of real time thrombopoiesis. They are newly released in the circulation with a larger size & greater RNA content than mature platelets, and can be measured by automated haematology analyzer equipped with reticulocyte detection channel and described as immature platelet fraction (%-IPF) and immature platelet count (A-IPC).  Summary and Conclusion  129 A high %-IPF has been suggested as an indicator of thrombocytopenia due to rapid platelet consumption, while a low %-IPF is characteristic of bone marrow suppression states. %-IPF/A-IPF has the competency to be performed routinely and, therefore, can provide therapeutic and diagnostic feedback in the life threatening conditions. The present study aimed to show the utility of estimating %-IPF and A-IPC using a reticulocyte detection channel CBC autoanalyzer as a simple reproducible blood analysis to be employed in the differential diagnosis of pregnancy-associated thrombotic microangiopathic conditions. The current study was carried out on 57 pregnant women and divided into three groups; group 1 included 24 pregnant women with SPE/HELLP, group 2 included 13 pregnant women with TTP/HUS, group 3 included 20 pregnant women having normal pregnancy with normal blood pressure and platelet count. All patients were subjected to complete history taking, thorough clinical examination and laboratory investigations focusing mainly on CBC count, estimation of %-IPF and schistocytes count. In the current study, IPF% was able to discriminate between patients with TTP/HUS or SPE/HELLP at optimal  Summary and Conclusion  130 cutoff values >15.9 %. The sensitivity and specificity were 76.92% and 66.7%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 55.6 % and 84.2%, respectively (AUC=0.692). Schistocyte count was able to discriminate between patients with TTP/HUS or SPE/HELLP at cut off value >4.6 %. The sensitivity and specificity were 61.54 % and 91.67%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 80% and 81.5%, respectively (AUC=0.771).