Evaluation of early diagnostic criteria including HLA-B27 for ankylosing spondylitis in a follow-up study.

Early diagnostic criteria, a combination of the HLA-B27 test with clinical data, ESR and radiological signs, were evaluated in a 5-6 year follow-up study of 77 patients with possible ankylosing spondylitis (AS) and 45 with other rheumatic diseases. 34 (44%) with possible AS at first examination developed definite AS according to the New York criteria and 29 (38%) were classified as still possible AS. From these data a sensitivity of 82%, a specificity of 68%, a positive predictive value of 50% and a negative predictive value of 91% were calculated. Therefore the early diagnostic criteria, although of limited value for the diagnosis of definite AS, may clearly define patients at risk of AS or unclassified seronegative spondylarthropathies.