I sent this email to another member who had more questions about diagnosis:
Your frustration is understandable, but the proposed 2013 ICBD "point system" is actually quite forgiving in that it only requires 4 points for a diagnosis of "probable Behcet's," after other diseases have been ruled out. That means that you only really need two recurrent major symptoms (oral, genital, and/or eyes) to meet the baseline of 4 points. Or you can substitute a two minor recurrent symptoms (skin, neuro, vascular, or pathergy) for one of the major.
And these symptoms do NOT have to occur at the same time; they can pop up over a period of years. In many cases, the only symptom that requires repetition is oral ulcers at least three times a year, during at least one year. And those can be reliably reported by a patient. Even if you only had genital ulcers once (or never), eye inflammation once (or never), and so on, you can still be diagnosed with BD if you meet the other criteria. A few patients have even been correctly diagnosed without ever having oral ulcers.
I would guess that almost everyone in this group meets this baseline (4 points) or else they wouldn't have been suspected of having BD. I realize that I was extremely fortunate in 1988 for a gynecologist to suspect Behcet's after I'd only had recurrent bouts of oral ulcers plus two outbreaks of genital ulcers -- especially since I'm a blue-eyed Scandinavian. Shortly afterwards, I developed arthritis, which would have bumped my score to 5.
Notice that nowhere in the diagnostic classification are blood tests mentioned. That is because it is not uncommon for values for SED/ESR rates and other measures tested for in similar rheumatic diseases to be normal or near-normal in Behcet's. Having a negative HLA-B51 tests means nothing; you can still have Behcet's. Therefore, blood tests are unreliable markers of either presence of disease or degree of inflammation in Behcet's.
I have research links showing that these tests are not useful in BD, so if you need a copy for your doctor(s), just let me know.
Doctors may continue to order blood tests because they do things out of habit, but the results are not useful and should not be used in including or excluding a diagnosis of Behcet's. Lab tests for Behcet's patients are best used to monitor side effects of medication, organ function, and markers of concurrent diseases (anemia, thyroid, infection).
Results of biopsies and scans (CT/MRI) can also be negative or inconclusive. That doesn't mean we don't have BD. However, those tests can be useful to rule out other conditions (herpes, MS, other skin inflammatory conditions, etc.).
Still, we continue to run into doctors who insist that we can't have BD if we don't have _______(fill in the blank), even though this has nothing to do with the diagnostic criteria. Their concern should only be whether we score 4 or more points over a period of time and other diseases have been ruled out.
Anyone who's dealing with doctors who continue to fight against the diagnosis should give them a copy of the full 2013 ICBD paper, available as a document on the Yahoo behcet-support website. I'm certainly giving copies to my doctors even though I have a confirmed diagnosis, in hopes that it can help future patients.
Nervous and unsure.
Newly diagnosed and very confused 
Behcets and vitamin D deficiency
