Evaluation of a CD61 MoAb method for enumeration of platelets in thrombocytopenic patients and its impact on the transfusion decision-making process

BACKGROUND: Almost all automated hematology cell analyzers use methods based on either the impedance (PLTi) or the optical (PLTo) properties of the cells for performing platelet counts. To improve the accuracy of platelet counts in peripheral blood (PB), the use of CD61 (GPIIIa) MoAbs (ImmunoPLT method) has recently been introduced in an automated hematology blood-analyzer system (Cell-Dyn 4000, Abbott Diagnostics). STUDY DESIGN AND METHODS: A comparative evaluation was made of the accuracy and precision of the three methods currently available in the Cell-Dyn 4000 automated hematology cell analyzer for counting the number of platelets per microliter of PB in a total of 47 patients with chemotherapy-induced thrombocytopenia. A flow cytometric PB platelet count was also performed in parallel and used as an external reference. RESULTS: PB platelet counts showed a good correlation among the PLTo, CD61-ImmunoPLT, and flow cytometric methods. In contrast, the PLTi procedure usually provided an overestimation of the number of platelets per microliter. Although a good correlation was observed between the flow cytometric reference method and both the ImmunoPLT and PLTo methods, the highest degree of agreement was found for the ImmunoPLT techniques (94% vs. 67%). A comparative analysis of the PLTo and CD61-ImmunoPLT methods with regard to their value for predicting platelet transfusion needs on the basis of specific flow cytometric platelet count thresholds showed a good correlation when the cutoff level of 10,000 platelets per muL was used. In contrast, at the threshold of 20,000 platelets per muL, slight differences were observed between the PLTo and CD61-ImmunoPLT procedures for predicting transfusion needs. CONCLUSION: Such results indicate that, if the CD61 ImmunoPLT method is used in the platelet transfusion decision-making process, unnecessary platelet transfusions could be avoided in up to 17.5 percent of persons with a PLTo count of < 20,000 platelets per muL.