Radiological scoring methods in ankylosing spondylitis: Reliability and sensitivity to change over one year

Our aim was to compare reliability and sensitivity to change of different r adiological scoring methods in ankylosing spondylitis (AS). Two trained obs ervers scored 30 AS radiographs twice with an interval of 4 weeks. The same two observers scored 187 AS radiographs in pairs, at baseline and after on e year followup, to measure change and agreement on change. The sacroiliac (SI) joints were scored in 5 grades by the New York method and the SASSS (S toke Ankylosing Spondylitis Spine Score). Hips were graded 0-5 (according t o Larsen). Cervical and lumbar spine were graded (0-4, Bath Ankylosing Spon dylitis Radiological Index, BASRI), and scored in detail (0-72, SASSS). SAS SS of the cervical and lumbar spine scored on the anterior sites of the ver tebrae proved most reliable, with both intra and interobserver intraclass c orrelation coefficients (ICC) between 0.87 and 0.97. BASRI was only moderat ely reliable, with Cohen's kappa ranging between 0.50 and 0.82 for intra, a nd 0.38-0.64 for interobserver reliability. Similarly, SI joint scores (New York, SASSS) showed intraobserver kappa between 0.56 and 0.84, and interob server reliability with kappa between 0.37 and 0.47. Larsen hip scores prov ed unreliable: moderate intraobserver kappa of 0.47-0.58 and low interobser ver kappa of 0.29. After retraining, interobserver kappa did not improve (0 .45 and 0.17). In retrospect, a one year period was too short to measure se nsitivity to change. Observers agreed that no change occurred in up to 89% of cases. A measurable change of deterioration or improvement occurred rare ly. We conclude that in AS, only the SASSS method for the spine and the BAS RI reached good reliability. Other methods for spine, SI joints, and hips w ere moderately reliable at best. There was moderate to good agreement on no change between the observers. No method showed change over a period of one year in a considerable number of patients.