I see. She has other health issues as well so she has a lot of tests done. I was just curious if it was possible to do a test since so many people ask how do they know for sure.
I think she meant they gave her a blood test to rule out other contributing factors like run4you said and she was either misunderstanding what they said or they explained it to her badly.
I have never heard of anything in the blood diagnosing bipolar. I was diagnosed in 2000, and been to several pdoc's (relocations). Never had a blood test.
http://www.nimh.nih.gov/health/publications/bipolar-disorder/complete-index.shtml#pub7
"Bipolar disorder cannot currently be identified through a blood test or a brain scan, but these tests can help rule out other contributing factors, such as a stroke or brain tumor."