Background: Hematology analyzers use impedance, optical, and/or immunologic techniques for counting platelets (PLTs). PLT counting in whole blood has been validated thoroughly; however, this is not the case for PLT counting in PLT concentrates (PCs), in which red cells (RBCs) are absent. Therefore, this study is focused on PLT counting in PCs to study use of ethylenediaminetetraacetate (EDTA), carryover, and accuracy of the analyzers.
Study design and methods: In total six hematology analyzers (AcT 8, Beckman Coulter; ADVIA 2,120, Bayer; Cell-Dyn 4,000, Abbott; Onyx, Beckman Coulter; K4,500, Sysmex; and XT 2,000i, Sysmex) were tested for PLT counting. PC samples with various PLT concentrations were made (0-1,700 x 10(9)/L) and measured 10 times. Carryover was determined five times.
Results: PC samples (1,000 x 10(9) PLTs/L) in EDTA tubes showed significantly higher PLT counts than samples in "dry" tubes for all analyzers except for the Cell-Dyn 4,000 with the impedance technique. Carryover was not more than 0.3 percent for all analyzers. The K4,500 showed the most accurate results, whereas the Cell-Dyn 4,000 with the impedance technique had low accuracy due to an overestimation of more than 20 percent.
Conclusion: Most tested analyzers seemed to be suitable for counting PLTs in PCs. All hematology analyzers should be validated for counting PLTs in absence of RBCs as is the case in PCs, in addition to validation of PLT counting in whole blood.