A prospective study of early diagnostic investigations in the diagnosis of ankylosing spondylitis.

This study was designed to assess the relative values current of locally available investigations in the early diagnosis of inflammatory sacroiliitis. Consecutive patients attending routine rheumatology clinics in Aberdeen clinically considered by consultant rheumatologists to have inflammatory back disease but with insufficient criteria to firmly establish a diagnosis of ankylosing spondylitis were included. Patients were assessed using a standard questionnaire, clinical examination of spinal movements, plain radiology of the sacroiliac joints, computerised tomographic scanning of the sacroiliac joints and HLA-B27 typing. Patients were systematically followed up using repeated clinical and radiological examination for five years. Plain film evidence of grade 2 radiological sacroiliitis (bilateral or unilateral) was found to be the most reliable predictor for the development of ankylosing spondylitis satisfying the New York criteria at 5 year follow up. CT scanning and HLA-B27 typing were of no added value in this series and the clinical questionnaire lacked specificity. It is concluded that the combination of clinical history, examination and plain film radiology are currently reliable criteria for diagnosing the subsequent development of ankylosing spondylitis satisfying established criteria.