Evaluation of early diagnostic criteria for ankylosing spondylitis in a 10 year follow-up.

A set of early diagnostic (ED) criteria comprising clinical data, ESR, radiological spinal signs, and the risk factor HLA B27 was evaluated after 5 and 10 years in a follow-up of 54 patients with an initial diagnosis of possible ankylosing spondylitis (AS). After 10 years 32 patients (59%) had developed definite AS according to the New York criteria, 10 individuals (19%) had possible or undifferentiated spondylarthropathy (SA), whereas in 12 patients (22%) other diagnoses were stated. ED criteria had a high discriminatory significance for the development of AS after 5 and 10 years (P less than 0.005, P less than 0.001 respectively). In this respect they were more valuable than B27 determination alone (P less than 0.01) or the ED criteria without HLA B27 (P less than 0.05). Furthermore, patients with still possible or undifferentiated SA had a higher mean score at the first examination than individuals with other final diagnosis (P less than 0.05). Thus, the ED criteria were useful for the identification of patients developing definite AS and of individuals in the AS related group of possible or undifferentiated SA.