Development and validation of a simple tape-based measurement tool for recording cervical rotation in patients with ankylosing spondylitis: comparison with a goniometer-based approach.

OBJECTIVE: To compare a tape-based tool for measuring cervical mobility in patients with ankylosing spondylitis (AS) with the widely practiced goniometer-based approach. METHODS: We developed a novel tape-based approach to measurement of lateral cervical rotation of the neck that is minimally affected by flexion/extension movements of the neck. This requires measurement of the difference between a mark at the suprasternal notch and the tragus of the ear. Rotation score is measured in centimeters and constitutes the difference in length between the 2 extremes of cervical rotation (http://www.arthritisdoctors.org/researcher.html). We assessed the tape-based and goniometer-based methods in a total of 263 patients from 3 countries, Canada (n = 205), Australia (n = 29), and Colombia (n = 29), that included patients from community and tertiary-based practice. Intra- and interobserver reliability was assessed in a subset of 44 patients by ANOVA and a 2-way mixed effects model. The Bath AS Disease Activity (BASDAI) and Function (BASFI) Indices, and the modified Stoke AS Spinal Score (mSASSS), were also recorded to assess construct validity by correlation coefficient and regression analysis. Responsiveness was assessed in a subset of 33 patients that were either randomized to anti-tumor necrosis factor-a therapy:placebo (n = 22) or received open label infliximab (n = 4) or pamidronate (n = 7) over a period of 24 weeks. RESULTS: Scores obtained with the tape-based method were normally distributed, while those obtained using the goniometer were skewed towards normal values. Reliability for the goniometer-based approach was excellent [intraclass correlation coefficient (ICC) > 0.90] and very good for the tape-based approach (ICC > 0.80). Significant correlations were noted between age, disease duration, function and structural damage scores, and scores obtained with both methods. Responsiveness was high using raw scores obtained with the goniometer (standardized response mean > 0.80) but was not evident when the grading scheme proposed for the Bath AS Metrology Index (BASMI) was employed. CONCLUSION: The tape-based approach we describe provides a simple, feasible, and reliable index of cervical rotation that is comparable to the information obtained from the use of a goniometer. If the goniometer-based approach is used, raw scores should be used in the calculation of responsiveness rather than the grading scheme suggested in the BASMI.

Development and validation of the Edmonton Ankylosing Spondylitis Metrology Index.

OBJECTIVE: Assessment of spinal and hip mobility has been recommended by the Assessments in Ankylosing Spondylitis (AS) Working Group for clinical trials and record keeping, although suggested measures primarily reflect structural damage. Our objective was to validate a simple, 4-item composite measure of spinal and hip mobility, the Edmonton AS Metrology Index (EDASMI). METHODS: We assessed the EDASMI and the Bath AS Metrology Index (BASMI) using a total of 263 patients from 3 countries: Canada (n = 205), Australia (n = 29), and Colombia (n = 29). Intra- and interobserver reliability were assessed in a subset of 44 patients. Construct validity with respect to disease activity (Bath AS Disease Activity Index [BASDAI]), function (Bath AS Functional Index [BASFI]), and structural damage (modified Stoke AS Spinal Score [mSASSS]) was analyzed using correlation and hierarchical regression. Responsiveness was assessed in a subset of 33 patients who received either anti-tumor necrosis factor alpha therapy (n = 26) or pamidronate (n = 7) over 24 weeks. RESULTS: In contrast to the EDASMI, BASMI scores covered a limited range, with 70% of patients demonstrating a score < or =3 (range 0-10) and 4 of 5 individual measures demonstrating substantial floor effects. Both measures were highly reliable (intraclass correlation coefficient >0.90) and demonstrated similar construct validity (EDASMI correlated with disease duration [0.52], BASDAI [0.24], BASFI [0.61], Bath Ankylosing Spondylitis Radiology Index [0.79], mSASSS [0.75]; P < 0.001 for all). The change in EDASMI score was significant after 24 weeks of therapy (standardized response mean 0.40; P = 0.03), but change in the BASMI was not significant. CONCLUSION: The EDASMI is a simple, rapid, and reliable tool for the assessment of spinal mobility in AS that is responsive to therapeutic intervention.