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

Abstract

BackgroundModern automated haematology instruments are capable of performing leukocyte differentials faster, cheaper and with a higher precision than the traditional 100-cell manual differential count. Thus, in human laboratories, criteria are defined for performing a manual review of the blood smear resulting in a marked reduction of manual differential counts. While common in human laboratories, this approach to reducing the number of manual differentials in veterinary laboratories is still not commonly performed. Thus, our aim was to determine the rate and causes of manual leukocyte differentials in a university clinical pathology laboratory using the automated laser-based haematology analyser ADVIA 120. Overall, 14,953 complete blood cell counts from dogs, cats and horses were reviewed. Manual leukocyte differentials were requested if abnormal ADVIA peroxidase and baso cytograms were detected (i.e. suspicion of left shift or atypical lymphocytes/blasts, inappropriate separation of cell populations).ResultsIn 21% of canine, 32% of feline and 20% of equine samples, a manual differential was requested. Indistinct separation of the cell population was present in 10% to 15% of the cases. Depending on the species, atypical lymphocytes were suspected in 2% to 12%, left shift in 13% to 25% and suspicion of blasts was present in less than 0.4% of the cases.ConclusionsThe obtained results are comparable to those published for human medicine and the rate of manual differentiation could be markedly reduced in veterinary laboratories if microscopic examination was used as a validation procedure rather than as a reflexive substitute for automated differentiation.

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“…In contrast, microscopic evaluation of blood smears is still considered mandatory in veterinary medicine because graphical and flag algorithm interpretation is not well established. 17,22 Given the potential confounding effect of HBs on automated hematology results, we evaluated the influence of feline HBs obtained with an automated analyzer on the leukocyte count and other CBC results, including cytograms and indices. Our hypothesis was that HBs in elevated numbers could be suspected or even detected with the evaluation of automated CBC graphical and numerical results.…”

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