Evaluation of the Coulter three-part differential screen.

An evaluation of the Coulter Electronics, Inc. (Hialeah, FL) three-part differential screen (3PD) was undertaken to determine the performance characteristics of this system. The 3PD measures white blood cell (WBC) volumes and, by automatic analysis of the resultant WBC histogram, produces a determination of the number and percent of lymphocytes, mononuclear cells, and granulocytes. A group of 984 random patient blood samples was tested. The overall review rate (samples requiring some further analysis or review) was 42%. The main source of false negatives on the 3PD was eosinophilia: 5 out of 22 instances of eosinophilia greater than 750/microL were not flagged. The precision of the three parameters, measured as percent coefficient of variation, was 3.3% for lymphocytes, 14.2% for mononuclear cells, 3.1% for granulocytes, and 2.4% for the total WBC. The stability of blood samples was acceptable for up to eight hours at room temperature (less at 4 degrees C).