Analytic variability in the enumeration of neutrophil subpopulations in canine blood

Abstract

BackgroundConventional differential leukocyte counts do not enumerate hyposegmented neutrophils (Hypo‐PMN), ie, immature neutrophils that already lost the band morphology but are not yet completely segmented. They may be early indicators of acute inflammation.ObjectivesThe purpose of the study was to evaluate the analytic variability of counts of segmented neutrophils (Seg‐PMN), band neutrophils (Band), hyposegmented neutrophils (Hypo‐PMN), non‐Bands (Hypo‐PMN + Seg‐PMN), and Young‐PMN (Bands + Hypo‐PMN) assess if Hypo‐ or Young‐PMNidentify inflammation better than Bands.MethodsNeutrophil subpopulations were counted by 2 observers on 2 sets of 100 cells in 267 blood smears from dogs with changes potentially consistent with inflammation to calculate the intra‐ and inter‐observer variability.ResultsMedian intra‐observerCVs were < 5.0% for Seg‐PMNand non‐Bands, and 20.0% and 28.0% for Hypo‐PMNand Young‐PMNfor observer 1 and 2, respectively; median inter‐observerCVs for Seg‐PMN, non‐Bands, Hypo‐PMN, and Young‐PMNwere 4.6%, 5.0%, 60.0%, and 47.1%, respectively. MedianCVof Band counts in blood smears with bands was 141%.ConclusionsThe analytic variability of Hypo‐ and Young‐PMNis lower than that of Bands. This retrospective study did not allow us to investigate the diagnostic potential or the clinical relevance of these cells. However, the low inter‐ and intra‐observer variabilities with these cell populations suggest that the count of Hypo‐ or Young‐PMNmay better identify acute inflammation than the count of Bands.