There are some imbalances that cause disorders, like a lithium deficiency is linked to bipolar disorder (not all BPD cases are a result of lithium, though.) Really though it would take a long term psychoanalysis performed by a trained and experienced psychiatrist.
Loved your sub question. Don't explain it -- it's tantalising like it is.
NO, there is no blood test but the good news is that there's an infallible insanity test available on line. It's called ask.com. We only have to spend a few weeks on here answering questions to learn whether some contributors are sane.