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.