Large-scale study paves the way for tailored reference ranges for dogs

THE first large-scale analysis of canine blood cell parameters in different breeds has been conducted by the Royal Veterinary College.

Oliver Garden and colleagues at the RVC, working with Lucy Davison of the University of Oxford, extracted information on the complete blood cell counts of 6,046 dogs with normal red and white blood cell parameters from a veterinary database.

The paper, "Breed-specific hematological phenotypes in the dog: a natural resource for the genetic dissection of hematological parameters in a mammalian species," has been published in online journal PLOS ONE.

Certain haematological phenotypes are well recognised in dogs, but no large-scale, systematic studies of the phenotypic diversity of peripheral blood in this species have been undertaken.

The authors' objective was to undertake a comparative analysis of normal haematological profiles within a large veterinary database to identify possible breed-specific phenotypes as a prelude to genetic analysis of these traits in the future.

Seventy-five pure breeds plus a mixed-breed control group were represented by 10 or more dogs. Principal component analysis revealed 37 pure breeds had distinctive patterns of blood cell parameters. Certain individual breeds and a mixed-breed group showed significant differences between all haematological parameters except mean corpuscular haemoglobin concentration.

Results found concentrations of white blood cells, neutrophils, monocytes, lymphocytes, eosinophils and platelets – but not red blood cell parameters – all varied with sex. Male dogs had higher concentrations of white blood cells, neutrophils, monocytes and eosinophils, but lower concentrations of platelets, than female dogs.

Neutering status had an impact on haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, and concentrations of white blood cells, neutrophils, monocytes, lymphocytes and platelets.

Parameters other than mean corpuscular haemoglobin concentration all varied with age. Although there is general acknowledgement that puppies have a lower red cell mass and haemoglobin concentration than adult dogs, the authors state, this is the first study to show a sustained increase in these parameters to up to four years of age, followed by a gradual decrease to 12 years of age and older.

The results of the study should lead to practices being able to "tailor" diagnostic tests and apply more specific reference ranges according to breed, sex, neutering status and age, the authors propose.
Professor Garden said: “We have demonstrated the need to generate customised reference intervals that account for breed, sex, neutering status and age in our day-to-day veterinary clinical practice. This is where the future lies: the days of generic, all-breed reference intervals for the canine complete blood cell count are numbered and will be a relic of the past in the next five to 10 years.

"Our ongoing work in this area will advance veterinary clinical practice and could have implications for human medicine in due course. Studies that would require thousands of human subjects typically require fewer than 100 in the dog, which is why this species is rapidly gaining traction as a model in a number of biomedical disciplines.

On taking the work further to make it applicable to veterinary practice, Prof Garden told MRCVSonline: "We are absolutely going to pursue this work further and are looking for commercial funding partners at the current time."

The full article may be found at Lawrence, J; Chang, YM; Szladovits, B; Davison, LJ; Garden, OA (2013).
Breed-Specific Hematological Phenotypes in the Dog: A Natural Resource for the Genetic Dissection of Hematological Parameters in a Mammalian Species. PLoS One. DOI: 10.1371/journal.pone.0081288