Assessment of outcome in ankylosing spondylitis: an extended radiographic scoring system.

OBJECTIVE To develop and validate an extensive radiographic scoring system for ankylosing spondylitis (AS). METHODS The Stoke Ankylosing Spondylitis Spinal Score (SASSS) was modified by adding a score for the cervical spine and defining squaring. This modified SASSS (mSASSS) is the sum of the lumbar and cervical spine score (range 0-72). 370 lateral views of the lumbar and cervical spine were used for development of the mSASSS, standardisation of observers, and for studying reliability. In a 48 week NSAID study of 57 patients, change over time and construct validity were studied. RESULTS Interobserver correlations of the lumbar and cervical spine scores were good (r>0.95). The interobserver duplicate error was 0.55 in a range from 0 to 36. The mean change in the cervical and lumbar spine scores between weeks 0 and 48 of all patients was 1.45 (range 0-6.0) and 1.06 (0-5.0), respectively (paired t testing, p<0.001). Change in radiological score was seen in 36/57 (63%) patients (lumbar and cervical spine 11, cervical spine 12, lumbar spine 13 patients). CONCLUSION The mSASSS is useful for assessing extensive radiographic damage in AS. It is reliable, detects changes over 48 weeks, and shows a satisfactory face and construct validity.