Donated blood said hlab27 antigen positive pcp had blood drawn hlab27 negative. joint pain everywhere. weight gain headaches weakness tingling hands?

Cannot be: HLA- B27 is always positive or negative. It does not change. One of the tests was wrong. Also, HLA-B27 is useless as a screening test. The symptoms need to be worked up (eg., the joint pain) and then, only the proper tests should be done depending on the symptoms. Diseases such Lyme disease or lupus cannot be checked for with labs. A history & physical are the first steps.