WBC and Platelet Counting Performance by Hematology Analyzer

White Blood Cell and Platelet Counting Performance by Hematology Analyzers: A Critical Evaluation

Bernard W. Steele, Niou-Ching Wu, Clarence Whitcomb

Laboratory Hematology 7:255-266
© 2001 Carden Jennings Publishing Co., Ltd.

ABSTRACT:

The platelet and leukocyte counts obtained from 3 clinical hematology analyzers (Coulter Gen-S, Bayer ADVIA 120, and Abbott CellDyn 4000) and from 1 instrument in the final phases of development (Coulter LH 750) were compared with counts obtained using flow cytometric methods. We studied samples from 3 subject populations: a platelet control group of 30 subjects with normal or nearnormal hematological values, a group of 31 patients with platelet counts less than 30 x 10⁹/L, and a group of patients with conditions known to affect leukocyte counts. This group included 10 patients with sickle cell disease, 10 with presumed thalassemia, and 10 with renal and/or liver disease. In the platelet control group, the differences between counts obtained using the flow cytometric method and clinical analyzers were of little clinical significance. According to results of a paired t test, the samples from patients with low platelet counts showed that 3 of the 4 analyzers had a positive bias for platelet counts. This bias can be clinically important because it may lead to withholding platelet transfusions from thrombocytopenic patients. All 4 analyzers counted low numbers of platelets with good accuracy but with different flagging patterns. Our limited data suggest that for routine analyzers a platelet count of 15 x 10⁹/L or lower may be the most suitable value to correctly identify patients who need transfusions (assuming a reference platelet count of <=10 x 10⁹/L as a true cutoff). The third sample set, from patients with conditions that potentially cause interference in the white blood cell count, showed different patterns, with the analyzers flagging 0% to 60% of the samples from sickle cell patients, 0% to 30% of the samples from thalassemia patients, and 0% to 20% of the samples from patients with liver/renal disease.

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