Elimination of instrument-driven reflex manual differential leukocyte counts. Optimization of manual blood smear review criteria in a high-volume automated hematology laboratory.

Automated peripheral blood leukocyte differential counts (LDCs) are widely accepted in routine practice. However, many laboratories still reflexively perform manual LDCs based solely on abnormal automated results or instrument "flags," before any manual triage step. We describe our transition to a procedure that uses manual methods to validate, rather than to replace, automated LDCs (an approach recommended early in the development of automated methods, but still not used in many clinical laboratories). Manual microscopic scans were performed in lieu of manual LDCs. Each scan that revealed cell types not quantifiable by the instrument triggered a manual LDC. However, if the manual scan simply confirmed the cell types seen on automated LDC, then the automated result was released, even if clinically significant quantitative abnormalities were present. This policy reduced manual LDCs by more than 70% and was validated by a manual retrospective audit. Patient care and laboratory operations can be optimized by using manual microscopic examination as a validation procedure rather than as a reflexive substitute for automated methods. There is no clinical rationale for reflex performance of manual LDCs based solely on instrument warnings.