From the SAA page:

"First, hla-b27 is a perfectly normal gene found in 8% of the Caucasian population. Generally speaking, no more than 2% of people born with this gene will eventually get spondylitis.

Secondly, it is important to note that the hla-b27 test is not a diagnostic test for AS. (emphasis added) Also, the association between AS and hla-b27 varies in different ethnic and racial groups. It can be a very strong indicator in that over 95% of people in the Caucasion population who have AS test hla-b27 positive. However, only 50% of African American patients with AS possess hla-b27 , and it is close to 80% among AS patients from Mediterranean countries."

The presence of HLA-B27 can help strengthen the case for an AS diagnosis, but the absence of it should not be a mark against the diagnosis.

Ginny - 58 year old female
Dx with USpA in March 2013; changed to AS in July 2015
Iritis and Scleritis, both currently in remission
unicompartmental knee replacements: right-June 2014, left-Aug 2018
MTX, Humira, Cyclobenzaprine, plus Celebrex as needed
Supplements: Folic Acid, Vitamin A, Vitamin D, Calcium, Fish Oil, Culturelle probiotic, Melatonin (as needed)