Objective—To determine the frequency of clinically relevant abnormalities missed by failure to perform a blood smear evaluation in a specific subset of dogs receiving chemotherapy and to compare automated and manual neutrophil counts in the same population
Design—Retrospective case series
Animals—50 dogs receiving chemotherapy with a total nucleated cell count > 4,000 nucleated cells/μL.
Procedures—50 blood smears were evaluated for abnormalities that have strong potential to change the medical plan for a patient: presence of blast cells, band neutrophils, nucleated RBCs, toxic change, hemoparasites, schistocytes, and spherocytes. Automated and manual neutrophil counts were compared.
Results—Blood smears from 10 (20%) patients had ≥ 1 abnormalities. Blast cells were identified on 4 (8%) blood smears, increased nucleated RBCs were identified on 5 (10%), and very mild toxic change was identified on 2 (4%). Correlation coefficient of the neutrophil counts was 0.96. Analysis revealed a slight bias between the automated and manual neutrophil counts (mean ± SD difference, −0.43 × 103/μL ± 1.10 × 103/μL)
Conclusions and Clinical Relevance—In this series of patients, neutrophil count correlation was very good. Clinically relevant abnormalities were found on 20% of the blood smears. An automated CBC appears to be accurate for neutrophil counts, but a microscopic examination of the corresponding blood smear is still recommended; further studies are needed to determine whether the detection or frequency of these abnormalities would differ dependent on chemotherapy protocol, neoplastic disease, and decision thresholds used by the oncologist in the ordering of a CBC without a blood smear evaluation.