Platelet volume analysis for differential diagnosis of malignant versus reactive thrombcytosis

ABSTRACT

Platelet characteristics were assessed in 20 patients with malignant thrombocytosis 55 patients with reactive thrombocytosis and 46 normal subjects. Patients with malignant thrombocytosis showed in comparison with controls significantly higher rates of both megathrombocytes [P<0.05] and microthrombocytes [P< 0.005], increased heterogenecity of platelet volume and increased platelet distribution width [PDW]. [P< 0.001].Patients with reactive thrombocytosis showed in comparison with controls significantly higher rate of microthrombocytes [P< 0.001], significantly lower rate of megathrombocytes [P< 0.001] with a significantly lower mean platelet volume [MPV] [P< 0.001]. Their platelet distribution width is similar to that of normal controls. Patients with malignant thrombocytosis showed significantly higher rates of megathrombocytes, MPV, and PDW than cases with reactive thrombocytosis [P< 0.001, P< 0.005, and P< 0.001 respectively]. A platelet distribution width more than 17 fl can help in discrimination of cases with malignant thrombocytosis from cases with reactive thrombocytosis with a 95% sensitivity and 91.1% specificity rates. The positive predictive value was 79.17% and the negative predictive value was 98.2%. Cases with malignant thrombocytosis showed significantly higher rate of failure of aggregation of Adenosine Diphosphate [ADP] than either cases with reactive thrombocytosis or controls. [P< 0.001 for each]. The failure of aggregation was also significantly higher in reactive thrombocytosis than in controls [P< 0.01]. Eliminated aggregation rate in the two disease groups and controls increased significantly with increasing MPV [r = 0.54, P< 0.0001] and was inversely correlated with the number of small platelets less than 7.5 fl [r =0.37, P< 0.02]. In conclusion, an increased platelet heterogenecity was found in most patients with malignant thrombocytosis. A normal PDW in patients with platelet count 500 X 10[9/L] strongly suggests reactive thrombocytosis