Automated analysis of blood samples from thoroughbred horses with the abbott cell DYN 3500 (CD3500) haematology analyser

This paper reports an evaluation of the Abbott CD35OO instrument in the haematological analysis of blood samples from 277 thoroughbred horses and foals. The age range studied was 20 days to more than 4 years, and CD35OO data were compared to those obtained from both the Coulter S88O and manual determinations of the leucocyte differential. The results showed excellent agreement (p>0.965) between the CD35OO and the S880 instruments for haemoglobin concentration, red blood cell (RBC) count, mean cell volume (MCV) and haematocrit (Hct). For the RBC count and MCV, however, the CD35OO gave slightly lower values than the S880 in the lower range of values and higher counts in the higher range of values. Correlations between the two automated platelet counts were acceptable although there was poorer agreement for platelet counts at higher (>250×109/1) values. In addition, some equine samples showed a higher CD35OO optical (WOC) compared to impedance (WIC) white cell count. This was shown to be due to the presence of lyse-resistant red cells, and further studies confirmed that the CD3500 resistant red cell mode was appropriate for analysis in such circumstances. Correlations between the CD3500 automated and manual differentials were also very acceptable with good correlations being obtained for granulocytes and eosinophils. Absolute CD3500 lymphocyte and monocyte numbers were however respectively lower and higher than determined by the reference procedure even though the total mononuclear cell (lymphocytes plus monocytes) count compared very well. Examination of age-associated variation for the RBC indices in this series of equine samples showed that the red cell count tended to be lowest in the older horses. In addition, there was also a clear trend for increasing MCV and decreasing red blood cell distribution width (RDW) values with progressive age in horses aged one year or older, with the values of these two indices being inversely related. Interestingly, this relationship was reversed in foals whereby during the first part of life, horses showed a decreasing MCV and an increasing RDW with progressive ageing up one year. These results confirm that the CD3500 analyser is well-suited to the analysis of blood samples from both foals and adult thoroughbred horses, and that the automated determination of leucocyte differentials in particular represents a significant advance in veterinary laboratory haematology.