There is good information online about the condition and forums for people with uveitis. Since recurring uveitis is an autoimmune condition, the blood test will tell, possibly, if there is an underlying cause. I'm a little foggy about this, but I seem to remember there is something that will show in the blood of a certain percentage of uveitis sufferers (a particular antigen?).
I don't know if you are still checking this post or not but I had uevitis and I am also a lab assistant. We draw to check autoimmune diseases, especially syphilis. Also, to check for a high SED rate which means that there is some sort of inflamation going on in your body. I hope things turned out alright for you. Good luck, Soph.