Comparative evaluation of platelet counts in two hematology analyzers and potential effects on prophylactic platelet transfusion decisions.

BACKGROUND: Decisions on prophylactic platelet (PLT) transfusions are generally based on the recipient's PLT count, but few clinicians are aware of precision and accuracy of the PLT counting methods used by the clinical laboratory. Each PLT counting technology has its specific inaccuracy, especially in thrombocytopenic samples and therefore may impact decisions on PLT transfusions.

STUDY DESIGN AND METHODS: Five routine PLT counting methods available in two hematology analyzers (Sysmex XN-2000 and Abbott CELL-DYN Sapphire) were investigated (impedance and optical on both analyzers and fluorescent on XN-2000), using the CD61 immunologic PLT method as a reference. The impact of counting inaccuracy on imaginary transfusion decisions was examined at various common PLT thresholds.

RESULTS: In total 341 samples were analyzed, 178 of which had PLT counts of less than 35 × 109 /L. Despite excellent overall correlation with the reference method (r > 0.99), thrombocytopenic samples showed only modest correlation for impedance and XN-2000 optical methods. Sapphire optical and XN-2000 fluorescent methods correlated very well with the reference, albeit with bias in the very low range. We noticed potential risk of undertransfusion (ranging from 2% to 90%), depending on the threshold used. The risk of overtransfusion was small (<10%).

CONCLUSIONS: The XN-2000 fluorescent PLT counting method showed excellent correlation with the CD61 reference count, closely followed by the CELL-DYN Sapphire optical method. XN-2000 impedance and optical and Sapphire impedance methods are not accurate enough for basing transfusion decisions on. Only XN-2000 fluorescent, Sapphire optical, and CD61 methods are sufficiently accurate for making appropriate clinical decisions in patients with severe thrombocytopenia.