Most prior veterinary studies have been of healthy individuals with health status usually determined by thorough physical examination but sometimes including further clinical pathology assessments. Some recent studies have included subjects with specific disease conditions. 1

Attention to the types of individual animals to be included is recommended in order to cover the breeds, sex and reproductive status, and ages commonly seen in the population of interest/general practice. Separate evaluations for paediatric populations will be needed, with defined ranges of age groups since there is virtually no information about expected biological variation in veterinary paediatric populations and some unpublished work suggests there are differences with paediatric subjects. Studies in human medicine have indicated that biological variation does not increase with age in adults, even in geriatric populations (> 70 years old).2 Although this is suspected to be the case in veterinary medicine, studies of geriatric populations, although increasingly seen in practice, have not been done.

Information about the study subjects should include breed, age, sex and neutered/spayed status, reproductive stage (pregnant, anoestrous, actively cycling, etc) as well as the environment (stabled, pastured, indoors only, outdoors only, zoological collection, wildlife in natural habitat, laboratory animals, etc) and general nutritional status and conditions. The bases for determination of health status (i.e., healthy or with specific disease or condition) should be included.


1.            Ruaux CG, Scollan K, Suchodolski JS, et al. Biologic variability in NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral valve degeneration. Vet Clin Path 2015; 44: 420-430.

2.            Fraser CG, Cummings ST, Wilkinson SP, et al. Biological variability of 26 clinical chemistry analytes in elderly people. Clin Chem 1989; 35: 783-786.