Need education on Personality Testing

Can anyone who is knowledgeable in psychological testing like MMPI, ect. tell me what the utility of it is in diagnosing bipolar disorder or a thought disorder. I work with a therapist who frequently tells me that that so and so patient has a thought disorder or bipolar disorder based on their testing. These assessments often seem way off to me based on my experience with the patient. She's always really concerned about these results despite my feeling that they're not clinically meaningful.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums