Elimination of Instrument-Driven Reflex Manual Differential Leukocyte Counts

Abstract

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.

Rate of manual leukocyte differentials in dog, cat and horse blood samples using ADVIA 120 cytograms

“…Lantis et al showed that laboratory operations could be optimised by modifying the algorithm for performing leukocyte differentials [13]. Instead of establishing criteria for manual differentiation, the authors proposed criteria for blood smear review.…”

“…Instead of establishing criteria for manual differentiation, the authors proposed criteria for blood smear review. Based on the results of blood smear review, manual differentials are performed or the automated differential is reported [13]. In veterinary medicine, experts’ opinions about blood smear reviews are diverse.…”

“…Whereas, in some places, manual leukocyte differentials are performed for every single sample, other laboratories scan every blood film and only perform manual leukocyte differentials if abnormal cell populations are present or if the automated leukocyte differential appears inaccurate. Besides these approaches, cytograms, which are routinely provided by haematology analysers, can be used to screen for abnormal cell populations and morphology [13] and to decide whether manual review and differentiation is necessary. Reviewing the cytograms seems to be especially important in veterinary medicine as the flag algorithms are not as well established or as comprehensive as those used in human medicine [1].…”

“…A large human multicentre study reviewing more than 90,000 CBCs from 263 institutions showed that manual reviews were performed in 16.2% of cases, including 6.5% manual blood film scans and 9.7% manual differential counts [11]. It was demonstrated that patient care and laboratory operations can be optimised by using manual microscopic examination as a validation procedure rather than as a reflexive substitute for automated methods [13]. The authors also stated that there is no clinical rationale for reflex performance of manual leukocyte differentials based solely on instrument warnings [13].…”

“…It was demonstrated that patient care and laboratory operations can be optimised by using manual microscopic examination as a validation procedure rather than as a reflexive substitute for automated methods [13]. The authors also stated that there is no clinical rationale for reflex performance of manual leukocyte differentials based solely on instrument warnings [13]. To our knowledge, there are currently no comparable studies in veterinary medicine.…”