I'll be honest, our approach has been to request signs/symptoms. The psych testing results (e.g., "moderate cognitive impairment", etc) are really only snapshots of the patient's condition. In some instances the patient may actually carry a diagnosis of dementia or Alzheimer's, but the standardized test doesn't provide a score of "Dementia." Are you with me?
You really have a number of choices: 1.) Ask for sign/symptoms 2.) Query for the final or definitive dx, or 3.) settling on a code like 294.9 (or similar). In the event you choose option 3, I'd be sure a discussion was held with the clinical staff to make sure they were comfortable with reporting that code.
Keep in mind that with these exams, it's a lot like doing an EKG for a patient with chest pain. The patient may indeed have a causal condition that creates the symptom (e.g., forgetfulness), but the diagnostic test, in and of itself, is incapable of providing a definitive diagnosis for us. Basically, we may end up reporting signs, symptoms and "ill-defined" conditions--or something similar--because a definitive diagnosis cannot be truly determined based on the exam findings.
I hope this has been helpful and good luck!