Analytic variability in the enumeration of neutrophil subpopulations in canine blood.

BACKGROUND

Conventional 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.

OBJECTIVES

The 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-PMN identify inflammation better than Bands.

METHODS

Neutrophil 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.

RESULTS

Median intra-observer CVs were < 5.0% for Seg-PMN and non-Bands, and 20.0% and 28.0% for Hypo-PMN and Young-PMN for observer 1 and 2, respectively; median inter-observer CVs for Seg-PMN, non-Bands, Hypo-PMN, and Young-PMN were 4.6%, 5.0%, 60.0%, and 47.1%, respectively. Median CV of Band counts in blood smears with bands was 141%.

CONCLUSIONS

The analytic variability of Hypo- and Young-PMN is 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-PMN may better identify acute inflammation than the count of Bands.