Background/Purpose: The IBDI was developed to assess the disability in patients with mechanical low back pain (1) which contains the 18 daily activities questions. The main symptom in Axial Spondyloarthritis (Ax-SpA) is inflammatory back pain which makes patient disabled in daily living. To assess the functional disability concerning to inflammatory back pain is important for accurate clinical approach to patients in daily practice. The aim of this study is to investigate the validation of Istanbul Back Disability Index (IBDI) in Ax-SpA patients.

Methods: The patients with Ax-SpA according to ASAS criteria were recruited into the study. Demographic, clinical and functional characteristics of patients were evaluated. Face and content validities were assessed via cognitive debriefing interviews with Ax-SpA patients. Classical psychometrics assessed, convergent validity (correlation of IBDI with Dougados Functional Index (DFI), Health Assessment Questionnaire (HAQ), ASAS Health Index (ASAS-HI), BASDAI, BASFI) and discriminative validity (correlation of IBDI with disease duration (month), Body Mass Index (BMI), Schöber’s test (cm), finger-floor distance (cm), tragus-wall distance (cm), chest expension (cm), MASES enthesitis score,). Spearman’s correlation coefficient was used to assess the relation between quantitative variables. The SPSS 24.0 statistical package was used for analysis. P<0.05 was accepted as significant.

Results: Sixty patients (37 male, 23 female) with mean of age 39.18 (SD:8.95) years were recruited. The 43.3 % of patients were smoking. The mean of disease duration was 85.93 (SD:79,06) months and the mean of BMI was 26.98 (SD: 4.18) kg/m². The means of BASDAI and the BASFI were 4,49 (SD: 2,37) and 2,83 (SD: 2,67) respectively. Cognitive debriefing showed the IBDI to be clear, relevant, and comprehensive which shows its face and content validity. The IBDI has good correlation with DFI (rho: 0,809; p<0,0001), HAQ (rho: 0,770; p<0,0001), ASAS-HI (rho:0,673; p<0,0001), BASDAI (rho:0,572; p<0,0001) and BASFI (rho:0,821; p<0,0001). This results show that IBDI has good convergent validity. The IBDI has not significant correlation with non functional parameters such as disease duration (rho: 0,202; p:0,121), BMI (rho: -0,142; p:0,280), Schöber’s test (rho:-0,150; p:0,252), finger-floor distance (rho: 0,189; p:0,149), tragus-wall distance (rho: 0,157; p:0,230), chest expension (rho: -0,232; p:0,075) and MASES (rho: 0,168; p:0,200). These results show that IBDI has discriminative validity.

Conclusion: The IBDI is practical, accurate and not time consuming scale which is valid to evaluate the functional disability in patients with Axial Spondyloarthritis.

(1) Duruöz MT et al. Development and validation of a functional disability index for chronic low back pain. J Back Musculoskelet Rehabil 2013;26:45-54.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-validation-of-istanbul-back-disability-index-ibdi-in-axial-spondyloarthritis-patients/