Evaluation of a Laser-Based Three-Part Leukocyte Differential Analyzer In Detection of Clinical Abnormalities

The three-part leukocyte differential function of an ORTHO ELT-8/dsa hematology analyzer was evaluated. Precision (coefficient of variation) at concentrations of 2 to 10 × 109 cells/L ranged between 2% to 4%. Counts after dilution were linear and there was no measurable carryover. Accuracy was evaluated on 1,502 clinical specimens by comparing instrument results with manual wedge differential counts on 100 cells. The results correlated closely for granulocyte (r = 0.99) and lymphocyte (r = 0.91) counts. The instrument had a positive bias in monocyte counting (r = 0.65), judged to be due to inaccuracy of wedge smears. Screening for qualitative abnormalities of white cells was adequate except for assessing myeloid immaturity and identifying nucleated red blood cells. However, these abnormalities usually were associated with quantitative hematologic abnormalities that would have prompted morphologic review. Lack of routine band neutrophil and eosinophil counting did not result in loss of significant medical information as judged by chart review. The three-part leukocyte differential was implemented in a 198-bed community hospital as a labor-saving measure. Implementation was uneventful and performance has been satisfactory.