Quantitation of the Percentage of Reticulated Platelets to Diagnose the Cause of Thrombocytopenia

Cho, Yong Gon; Kim, Jung Hyun; Kim, Dal Sik; Choi, Sam Im; Lee, Hye Soo

Abstract

BACKGROUND
Since reticulated platelets (RP), known to be newly released from megakaryocytes in the bone marrow into the blood, contain RNA in their cytoplasm, we can detect them by staining RNA remnants with fluorescent dyes and performing flow cytometric analysis. We attempted to search for the best conditions in quantitating the percentage of RP (RP%) to identify causes of thrombocytopenia. METHODS: The RP% were measured on venous blood samples collected in EDTA from 63 normal controls and 48 thrombocytopenic patients. The thrombocytopenic patients were divided into two groups according to the causes: hypoplastic and destructive. The RP% was determined by a flow cytometric analysis with anti-CD41a and thiazole orange (TO) as a fluorochrome. RESULTS: In patients with their platelet count less than 50 x 10(9)/L, the RP% of two patient groups showed a significant difference. The RP% and platelet count were correlated directly in the hypoplastic group, but inversely in the destructive group. According to the results of ROC curve, the best conditions in quantitating RP% to identify the cause of thrombocytopenia was to apply a 2% threshold of TO positivity among gated platelets; its sensitivity and specificity were 93.3% and 83.3%, respectively. w CONCLUSIONS: The RP% is considered to be a good marker for differentiating destructive from hypoplastic thrombocytopenia and monitoring of the destructive thrombocytopenic patient having normal bone marrow such as idiopathic thrombocytopenic purpura. For the accurate measurement of the RP%, the condition of 2% TO threshold is considered to be appropriate.