Development and Validation of the Edmonton Ankylosing Spondylitis Metrology Index WALTER P. MAKSYMOWYCH, 1 CATHY MALLON, 1 RHONDA RICHARDSON, 1 BARBARA CONNER-SPADY, 1 EDWIN JAUREGUI, 2 CECILIA CHUNG, 1 LISA ZAPPALA, 3 KEVIN PILE, 3 AND ANTHONY S. RUSSELL 1 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  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 <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. KEY WORDS. Spinal and hip mobility; Ankylosing spondylitis; Index; Validation. INTRODUCTION The Assessments in Ankylosing Spondylitis (ASAS) Working Group has recommended that spinal mobility constitute one of the outcome domains assessed both for clinical record keeping and in the assessment of disease- controlling antirheumatic therapies (1). ASAS has specif- ically recommended the measurement of occiput-to-wall distance, the modified Schober’s test, and chest expansion (CE) as the measures that should be used to assess spinal mobility. Although widely used, the occiput-to-wall dis- tance and modified Schober’s test primarily reflect irre- versible structural damage and demonstrate limited sensi- tivity to change in studies of intensive physiotherapeutic interventions (2– 4). CE is traditionally measured at the fourth intercostal space and often demonstrates poor re- producibility due to factors such as lack of standardization in the assessment technique and difficulties obtaining ac- curate estimates in some women (5). However, several studies have documented its responsiveness with both physiotherapeutic and pharmacologic interventions (2,6 – 9). The Bath Ankylosing Spondylitis Metrology Index (BASMI) is a validated composite index of 4 spinal mea- sures (cervical rotation [CR], tragus-to-wall distance, mod- ified Schober’s test, and lateral lumbar flexion [LLF]) and 1 Dr. Maksymowych is a Senior Scholar of the Alberta Heritage Foundation for Medical Research. 1 Walter P. Maksymowych, FRCP(C), Cathy Mallon, RN, Rhonda Richardson, RN, Barbara Conner-Spady, PhD, Ce- cilia Chung, MD, Anthony S. Russell, FRCP(C): University of Alberta, Edmonton, Alberta, Canada; 2 Edwin Jauregui, MD: CAYRE Arthritis and Rehabilitation Clinic, Bogota, Colom- bia; 3 Lisa Zappala, BSc, Kevin Pile, MD: James Cook Uni- versity, Queensland, Australia. Address correspondence to Walter P. Maksymowych, FRCP(C), 562 Heritage Medical Research Building, Univer- sity of Alberta, Edmonton, Alberta T6G 2S2, Canada. E- mail: walter.maksymowych@ualberta.ca. Submitted for publication July 30, 2005; accepted in re- vised form December 22, 2005. Arthritis & Rheumatism (Arthritis Care & Research) Vol. 55, No. 4, August 15, 2006, pp 575–582 DOI 10.1002/art.22103 © 2006, American College of Rheumatology ORIGINAL ARTICLE 575