Evaluation of the Coulter S-Plus IV three-part differential in an acute care hospital.

An evaluation of the three-part white cell differential count on the Coulter S-Plus IV was carried out in a 500-bed acute care hospital. Automated counts were compared with manual differential counts over a seven-month period. The S-Plus IV categorizes cells by volume after treatment with diluent and lysing solution. The three categories are labeled lymphocyte, mononuclear, and granulocyte, and, in normal samples, these correspond with lymphocytes, monocytes, and neutrophils. Eosinophils are counted either as mononuclear cells or granulocytes. Automated counts agree well with manual counts for the lymphocyte and granulocyte categories. Agreement is poor for the mononuclear category; this is likely due to the imprecision of the manual differential count. The S-Plus IV accurately classifies most samples as normal or abnormal. When all parameters of the hematology panel were evaluated, the false negative rate was less than 1%. Sixteen percent of results from the S-Plus IV were flagged, and 79% of these indicated an abnormality. False positive flags are usually due to a failure to adequately segregate mononuclear cells from granulocytes. Most commonly encountered abnormalities and hematologic disorders have abnormal three-part differential counts. The authors think the three-part differential cannot totally replace the manual differential but can decrease the number of repeat manual differentials on inpatients. It also offers quality control features useful to the hematology laboratory.