Ankylosing spondylitis: the correlation between a new metrology score and radiology.

The objective was to compare the Bath Ankylosing Spondylitis Metrology Index (BASMI) with radiology as a measure of disease outcome. Fifty-three patients, covering the entire spectrum of disease severity, were blindly and independently assessed using the BASMI (total of five standardized measurements, scoring range 0-10) and a radiology score of the four main spinal areas affected by ankylosing spondylitis (AS). BASMI correlates positively with the total radiology score (r = 0.74), while the individual BASMI scores for cervical rotation (r = 0.59), wall to tragus (r = 0.61), lumbar side flexion (r = 0.56), lumbar flexion (r = 0.68) and intermalleolar distance (r = 0.50) correlate positively with their respective radiology scores. BASMI and radiology do not relate well to each other as BASMI takes account of normal physical limitation and soft tissue involvement. In addition, although radiology scores are termed a 'gold standard', they are unreliable. Therefore, BASMI may be judged to be more important in assessing AS and become a 'gold standard' itself.