Studies on the relationship between the platelet shape and its function. VIII

Abstract

Native platelets are generally discoid in shape and easily transformed into spheres with pseudopods by various stimuli. Therefore, platelet shape may reflect the state of activation in vivo as well as the state of thrombopoiesis.This report deals with the platelet shape in disseminated intravascular coagulation (DIC) and hemolytic anemia examined by our method in which glutaraldehyde-fixed platelets are classified into discs (D), hemispheres (HS), spheres (S), bipolar forms (B), others (O), and ones with pseudopods (Ps). The index of platelet shape is calculated from percentage of each form of platelets as follows: Index=D-S/D+HS+SDIC included acute promyelocytic leukemia (APL; 3 cases), metastatic cancer (5 cases) and obstetrical diseases (2 cases), while hemolytic anemia included hereditary spherocytosis (2 cases), paroxysmal nocturnal hemoglobinuria (PNH; 4 cases) and post valvular replacement (PVR; 5 cases).In DIC, decrease in D (46.5±23.1%, M±ISD) and increase in S (17.0±19.3%) and HS (29.6±15.6%) were significant as compared with each value of normal subjects (P<0.01, P<0.01 and P<0.05, respectively) and the index (0.325±0.42) was lowered (Fig. 1). Ps did not so much increase as that induced by various platelet aggregating agents including thrombin in the in vitro experiment. The index did not corelate with any tests of blood coagulation and fibrinolysis in these patients. In two cases, however, platelet shape changes were noted at the earlier stage of DIC when only FDP and act-PTT showed a slight change, suggesting a usefullness of this examination for the diagnosis of DIC at an early stage.In hemolytic anemia, decrease in D (74.1±5.0%) and increase in 0 (11.5±5.0%) and Ps (30.1±6.3%) were significant (P<0.01, respectively). Hereditary spherocytosis, however, showed a normal platelet shape distribution, while PNH and PVR showed a considerable change, suggesting that intravascular hemolysis caused platelet shape changes due to coincident release of ADP from erythrocytes. Platelet shape changes may also reflect dysthrombopoiesis in PNH and blood coagulation in PVR.In conclusion, the platelet shape in DIC and intravascular hemolytic anemia, apart from the causes, is a sensitive index for a platelet activation in vivo and its examination may be a help for the early diagnosis of these pathological states.