Quantitative buffy coat analysis. A hematologic screen applicable to the selection of apheresis donors

Quantitative buffy coat analysis was performed on samples of venous blood with the QBC (Clay Adams Division of Becton Dickinson, Rutherford, NJ) Hematology System and the results for platelet counts, white blood cell counts, and microhematocrits were compared with those obtained by reference methods. At the established cut-off, values for apheresis donors the with-in run reproducibility (CV) of the platelet count was 6.8%; of the white blood cell count, 8.6%; and of the microhematocrit, 1.75%. Over the range of values studied, the platelet count showed the poorest correlation with the reference method (R = 0.72023) and the greatest dispersion of QBC values at a given reference value. Correlation coefficients for QBC and reference methods for white blood cell counts and hematocrits were 0.88887 and 0.89778, respectively. Predicted ranges of reference values for platelet counts and white blood cell counts, based on QBC measurements, were too wide at lower levels of the normal range to be clinically meaningful. When used in a screening mode to determine if results from apheresis donors exceeded specific cut-off values, the QBC system performed well as determined by high predictive values for results above the selected cut-offs. Misclassification errors with the QBC system were more likely to result in rejection of acceptable donors than acceptance of those with low platelet or white cell counts.