Five hundred and twenty-two dogs, including 163 dogs with hypoadrenocorticism, 351 dogs with nonadrenal gland illness, and 8 dogs with equivocal results were enrolled in this retrospective study.
Basal and post-ACTH cortisol concentrations and sodium and potassium concentrations were collected from medical records.
A receiver operating characteristic (ROC) curve was constructed for basal cortisol concentrations by standard methodologies.
Sensitivity, specificity, and predictive values were determined for various cut-points.
The area under the ROC curve was 0.988 and was similarly excellent regardless of serum electrolyte concentrations.
At the most discriminatory cut-point of 22 nmol/L (0.8 μg/dL), sensitivity and specificity were 96.9 and 95.7%, respectively. A basal cortisol concentration of ≤55 nmol/L (2 μg/dL) resulted in a sensitivity of 99.4%.
Conversely, a basal cortisol concentration of ≤5.5 nmol/L (0.19 μg/dL) resulted in a specificity of 99.1%.
Similar to findings in previous studies, basal cortisol concentrations >55 nmol/L (2 μg/dL) are useful in excluding a diagnosis of hypoadrenocorticism.
Interestingly, excellent specificities and positive predictive values were observed at lower cut-point cortisol concentrations.
Source: Gold, A.J., Langlois, D.K. and Refsal, K.R. (2016), Evaluation of Basal Serum or Plasma Cortisol Concentrations for the Diagnosis of Hypoadrenocorticism in Dogs. Journal of Veterinary Internal Medicine, 30: 1798–1805. doi: 10.1111/jvim.14589
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