Evaluation of an automated method for leukocyte differential counts based on electronic volume analysis
Sun, C.F.; Teng, J.T.
Journal of the Formosan Medical Association 87(1): 28-33
1988
ISSN/ISBN: 0371-7682 PMID: 3361290 Document Number: 315949
The Coulter S-Plus automated blood cell counter offers a three-part differential 3PD) of white blood cell (WBC) based on electronic discrimination of the cell volume. The instrument size approximately 10,000 to 20,000 WBC and partitions the histograms of cell volumes into three fractions: lymphocyte, 35-90 fl; mononuclear cell, 90-160 fl; and granulocyte, 160-450 fl. The lymphocyte fraction may contain lymphocyte, atypical lymphocyte, and lymphoma cell; mononuclear cell fraction, monocyte, blast, promyelocyte, and myelocyte; and granulocyte fraction, polymorphonuclear, band, metamyelocyte, eosinophil and basophil. To evaluate its practical usefulness as a screening tool for WBC differential, we evaluated its performance on specimen stability, precisions, flagging frequency, sensitivity, specificity, and its correlations with the manual differential. We found that specimens must be drawn within 6 hours and be kept at room temperature. Refrigerated storage is not suitable for specimens to be submitted for 3PD. The precisions, being better than conventional manual differential, are 1.7%, 2.2% and 13.7% for granulocyte, lymphocyte, and mononuclear cell, respectively. Sensitivity of 3PD is low, only 69.3%, with 30.7% of abnormal specimens missed by the screening procedure. Specificity is 76.1%. Efficiency of the test is 74.2%. Correlations with manual differential are good for lymphocyte fraction (correlation coefficient 0.922) and granulocyte (correlation coefficient 0.918). Correlation with manual differential is poor, however, for mononuclear fraction with a correlation coefficient of only 0.514. Even though most false negative specimens represent low density abnormalities, we fell that Cuolter 3Pd does not serve adequately as a screening tool due to its low sensitivity. The possible application of 3PD is discussed.