Haematological and blood biochemical testing of the equine athlete at rest is an integral part of equine clinical practice. Specific organ system evaluations are as important within this discipline as they are in any other discipline that involves internal medicine.
The high commercial and sentimental value of elite athletes means that they are seldom allowed to develop the diseases of neglect. However, they remain as vulnerable to sudden onset disease and to all of the other conditions that inevitably arise within horse populations,
as any of their non-athletic, non-elite equine counterparts. The essential difference between the elite performers and other horse populations is the importance in the athletic group, of sub-clinical, potentially performance-limiting conditions. Many, but not all, of these conditions
are infectious diseases. The elite equine athlete is uniquely predisposed to these conditions because transport to racing and competition venues and varying degrees of exposure to other horses, coupled with the stresses inherent in competition and racing are essential components of all
national and international horse sport.
Sample collection: Blood samples must be collected into the appropriate containers. Collection into evacuated containers has become the norm. Potassium EDTA is the anticoagulant for haematology. Lithium heparin is not suitable for this purpose, because it does not permit differential white cell counting. Samples for blood biochemistry testing can be collected into heparinised or plain tubes for either plasma or serum biochemistry respectively. Coagulation studies and the modified Clauss method of measurement the acute phase protein fibrinogen can only be carried out using sodium citrate containers.
Sample technique: Samples should be collected in an aseptic manner, so as to avoid inducing sepsis, local or general, into an otherwise healthy horse. Collection should be sympathetic, otherwise you run the risk of creating the potentially misleading artefacts that result from adrenal induced neutrophilia and splenic contraction.
Timing of sampling: The timing of elective sampling should reflect the questions that are being asked. There is little point in taking post exercise samples or sampling within two or three hours of exercise, if the issue is whether muscle enzymes are within the normal resting range. Samples for elective testing are best collected pre-exercise, early in the morning or alternatively, late in the afternoon when exercise has been completed in the morning.
Sample handling: Misleading artefacts can also arise from poor sampling handling in the period between collection and evaluation in the laboratory.The use of an insulated lightproof container, a laboratory blood sample rack and in hot climates, an ordinary household cold pack, can yield rich dividends in terms of the accuracy and value of the information generated from the sampling. Labelling should be legible and thought should be given to timing of transfer for analysis.
The below clinical pathology reference tables are a general guide. Each horse is an individual and will have its own norms.These reference tables are based on Thoroughbred foals and two or three year old horses in training. All were in good health
and condition on clinical examination. Click on each test to learn more or go directly to the haematology blood page.