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P122. Validation of the International Classification of Functioning, Disability and Health score: a measure of disability in inflammatory bowel diseases

R. Leong1, T. Huang1, Y. Ko1, V. Kariyawasam1, 1Concord Hospital Inflammatory Bowel Diseases Service, Concord Hospital Gastroenterology and Liver Services, Sydney, Australia

Background

Inflammatory bowel diseases (IBD) often impair functioning and disability objectively describes functional loss and lost productivity. The International Classification of Functioning, Disability & Health (ICF) questionnaire on IBD has not yet been validated for clinical use. This study aims to develop and validate a scoring system of the IBD Disability Index (IDI) and estimate its influence on work productivity.

Methods

Prospective IBD patients completed the IDI, Crohn's Disease Activity Index (CDAI) for Crohn's disease (CD) or partial Mayo score (pMayo) for ulcerative colitis (UC), IBDQ quality-of-life, Work Productivity and Activity Impairment questionnaires and clinical data.

Negative IDI represented greater disability. Discriminant ability and correlations with CDAI, pMayo and IBDQ scores were analysed using non-parametric statistics. Reversibility of IDI was assessed by test-retest reliability and sensitivity to change. Factor analysis and association with lost work productivity hours were determined.

Results

In total 150 consecutive subjects were prospectively recruited (75 CD, 25 UC; median age 37.0; 50 matched well controls). Divergent correlation of IDI with CDAI (r = −0.77, P < 0.001), pMayo (r = −0.77, P < 0.001) and convergent correlation with IBDQ (r = 0.85, P < 0.001) supported construct validity.

IDI discriminated CD, UC from controls (median −7, −5, +10; P < 0.001). IDI score >2.5 identified controls (94% sensitivity, 79% specificity; ROC area under curve 0.89). Paired re-testing in 35 subjects showed reliability in stable disease (P = ns) and sensitivity to change with relapse (P < 0.001). Intraclass correlation (0.89) and internal consistency (Cronbach's alpha 0.94) were both significant. Factor analysis identified dimensionality and items without variance. Readability of IDI was acceptable (Flesch scale 67). ICI inversely correlated with work hours missed of 10 hours for every −20 IDI score (r = −0.60, P < 0.001).

Diagnosis age, sex, phenotype, perianal disease, prior surgery, steroid-use, and disease duration all did not influence the IDI (P = ns). Prior biological agent failure predicted worse IDI than current use of biological agents (P < 0.05).

Conclusion

The IBD Disability Index is a valid score that directly estimates the cost of lost productivity. Current use of biological agents significantly reverses disability. The cost of IBD can be directly compared against other chronic diseases through the IDI design using the ICF Core Data set and it may become an effective cost-economics tool.

1. Peyrin-Biroulet, L., et al. (2012), Development of the first disability index for inflammatory bowel disease based on the international classification of functioning, disability and health, Gut, 61(2): 241–247.