HL-A antigens and sacroiliitis.

Lymphocyte typing for HL-A B27 is useful under conditions in which data based on history and examination are suggestive but not diagnostic of a seronegative spondyloarthropathy. The presence of HL-A B27 would increase the probability of a patient's having one of these entities, but its absence does not rule out such a diagnosis. Furthermore, tissue-typing allows one to predict the probability that a patient with inflammatory bowel disease will develop AS and the likelihood that the family member of a patient with AS will develop a related disease.