Biological variation of baseline serum cortisol concentration in healthy dogs, part 1: variance components

Introduction The measurement of baseline cortisol concentrations in dogs is affected by within-subject (individual, CV I ) and between-subject (group, CV G ) variability, together called “biological variation,” as well as analytical variability (CV A ). Methods Baseline cortisol concentrations analyzed in duplicate from 18 healthy, acclimated, client-owned dogs over a 6-week period were used to quantify biological variation for this measurand. Results Individual variation and group variation were CV I = 32.41% and CV G = 37.70%, and analytical variation (CV A ) was 6.86%. Cortisol concentrations were not associated with age, breed, sex, neuter status, or venipuncture site (jugular vs. cephalic). Baseline cortisol concentrations were not associated with date of sampling as the study progressed. Discussion Biological variation of baseline cortisol in dogs can be used to help interpret individual cortisol results and when establishing laboratory quality goals. Veterinarians should be aware of the potential biological variation of baseline cortisol measurements in dogs.