There is no ideal, one-size-fits-all testing method to differentiate between these two diseases, says Kelsey Hart, DVM.
Pituitary pars intermedia dysfunction (PPID, or equine Cushing’s disease) and equine metabolic syndrome (EMS) are by far the most common endocrine disorders in horses. In fact, a recent study results suggest that up to 30 percent of horses of some breeds suffer from one of these conditions during their lifetimes.
Source: The Horse, May 28, 2018. Link.
While scientists are constantly refining this area of research, “It is unlikely that a single diagnostic testing approach will ever be applicable to or useful in all presentations of these diseases,” she said. “It is important to remember that all of the tests described can have false positives and false negatives,” particularly in the early stages of both PPID and EMS.