Absolute immature platelet count helps differentiate thrombotic thrombocytopenic purpura from hypertension-induced thrombotic microangiopathy.

ADAMTS13 activity measurement is used in the diagnostic algorithm of thrombotic thrombocytopenic purpura (TTP), but results may not be available before initiation of therapeutic plasma exchange (TPE). The immature platelet fraction (%-IPF) and the calculated absolute immature platelet count (A-IPC) represent a test of real-time thrombopoiesis, and can be performed in most laboratories using automated analyzers. Here we report on using A-IPC kinetics to exclude idiopathic TTP in a patient with severe hypertension, thrombocytopenia, and acute renal failure, which was confirmed by a normal ADAMTS13. The complete resolution of thrombocytopenia occurred once blood pressure was controlled favoring a diagnosis of hypertension-induced thrombotic microangiopathy.