Hi,
While doing research on available DNA tests for genetic diseases in Yorkies, I came across a peer-reviewed article from April 2013 that provides a link to an updated list of DNA tests available for genetic diseases in dogs and cats. Yorkies clock in with only three tests--two for eye problems (Primary Lens Luxation and Progressive Retinal Atrophy, prcd), and one for a metabolic disease (L2-Hydroxyglutaric Aciduria). Genetic testing for Yorkies is still in its infancy

. Links to the labs that do the testing are provided:
Canine and Feline Hereditary Disease (DNA) Testing Laboratories