Assessment of Monocyte Counts Derived From Automated Instrumentation

Incorporating the use of benchtop flow cytometric analyzers within the routine hematology laboratory requires an evaluation of the optimal methods of determining monocyte counts. We analyzed 100 specimens with the Coulter STKS (Coulter Corp, Hialeah, Fla) using software version 1F, and the FACScan (Becton Dickinson, San Jose, Calif) using monoclonal antibodies (CD14/CD45). These methods were compared with manual 800-cell differential. The data reinforce the conclusion that monoclonal antibodies should be used in the determination of the reference method. Linear regressions were employed for data comparison. When we compared the FACScan and the Coulter STKS against 800-cell differentials, we encountered y-intercepts of 2.81 and 4.22 with r values of 0.77 and 0.80, respectively, (n=100). When the Coulter STKS was compared with the FACScan, the y-intercept was 2.02 with an r value of 0.95 (n=100). This suggests that automated analyzers yield a more accurate assessment of monocytosis.