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An Interlaboratory Study of a Candidate Reference Method for Platelet Counting

Authors & Contributors

Paul Harrison, PhD - Kenneth A. Ault, MD - Sabrinah Chapman, PhD - Lori Charie - Bruce Davis, MD - Keiji Fujimoto, MEng - Berend Houwen, MD, PhD - Jolanta Kunicka, PhD - Francis Lacombe, PhD - Sam Machin, MD - Robert Raynor, PhD - Luc van Hove, MD, PhD - Onno W. van Assendelft, MD, PhD, for the International Society of Laboratory Hematology Task Force for the Reference Platelet Count

First Published

03 January 2001


Oxford Academic - American Journal of Clinical Pathology (AJCP)



A multinational interlaboratory task force explored the important variables of platelet reference counting and developed a candidate flow cytometric reference method based on the RBC/platelet ratio.


A multicenter comparison was performed to determine whether the method met the necessary criteria and was precise enough to be recommended as a new reference method.


Each laboratory analyzed serial dilutions of normal specimens, stabilized material, and at least 60 patient specimens with a range of platelet counts from 1 to 400 103/μL (1-400 109/L). Pooled analysis of the serial dilutions showed that RBC-platelet and RBC-RBC coincidence events became negligible at sufficiently high dilutions (ie, >1:1,000).


All laboratories demonstrated excellent intra-assay and acceptable interlaboratory precision. Two antibodies (CD61 and CD41) were used for identifying platelets and individually gave acceptable results, but in a minority of samples, staining differences were observed. The optimum method thus uses a double-labeling procedure with a final dilution factor of 1:1,000.


The study demonstrated that this method meets the criteria for a reference platelet count.

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