New total T4 reference intervals

We periodically update our reference intervals to account for changes in equipment, methods and populations. Recently we have been working on revalidating our reference intervals for total thyroxine (TT4) in dogs and cats.

We are very grateful for the help of our wonderful veterinary client community who collected samples for us for this project. EDTA and serum samples were collected from animals that met the following criteria:

· 12 months to 8 years old 

· Healthy (e.g. staff pet, in for routine check-up, vaccination or desexing) 

· Not on any medication or recently vaccinated

· Not pregnant

· Not from SPCA or pound (i.e. animals that are not owned or have unknown history)New

· Not a sight hound (e.g. Greyhound), Maltese, Siberian Husky or Scottish Terrier

As well as TT4, all samples had a full CBC and biochemistry panel performed. All cases were reviewed by a Clinical Pathologist and any animal with any evidence of possible disease was excluded from the study. A significant proportion of the candidates were removed in this manner.

Several hundred animals were tested over an extended period of time (to account for any seasonal variations) and from throughout New Zealand (to account for geographical variations). A mixture of entire and neutered males and females from a variety of breeds were included. The final numbers of animals included in the dataset (after the exclusion of any with haematological or biochemical changes judged to be a concern by the clinical pathology team) were 111 dogs and 80 cats.

Analysis of this data (see plots below) indicated that the new reference intervals should be:

TT4 Dogs 15 -63 nmol/L

TT4 Cats 17-43 nmol/L

These new reference intervals will be introduced in Gribbles Veterinary laboratories nationwide from the end of August 2019.

If you have any questions please call Karen Bailey at Gribbles Veterinary Christchurch on 03 3799 484.