External validation of a United Kingdom primary-care Cushing's prediction tool in a population of referred Dutch dogs.

Background: A prediction tool was developed and internally validated to aid the diagnosis of Cushing's syndrome in dogs attending UK primary-care practices. External validation is an important part of model validation to assess model performance when used in different populations.

Objectives: To assess the original prediction model's transportability, applicability, and diagnostic performance in a secondary-care practice in the Netherlands.