Development and validation of a tool for assessing adherence to gluten free diet in patients with Celiac disease (Celiac Disease: Compliance Assessment Test; CD-CAT).

ABSTRACT

OBJECTIVE: Life-long adherence to gluten-free diet (GFD) and its assessment is essential for celiac disease (CeD) patients. We have developed and validated a tool for assessing adherence to GFD which can be used by both physicians and dietitians. DESIGN: Phase-I Development, content validation and assessment of reliability of tool. Phase-II Validation of tool against standard dietary evaluation (SDE) (gold standard), IgA anti-tissue transglutaminase antibody (IgA-anti-tTG Ab) and gluten immunogenic peptides in urine (Urine-GIP). Overall, 380 biopsy-confirmed CeD patients [Derivation-cohort n=100(PhaseI), n=210(PhaseII) and Independent validation cohort, n=70)were recruited. RESULTS: Of initial 90-point questionnaire, 84-items (CD-CAT.v1) were retained after content validation and pilot testing. In PhaseI, upon administering CD-CAT.v1on 100 patients, a comprehensive 35-items tool (CD-CAT.v2;α=0.86) was obtained after removing items with low test-retest reliability and item-rest correlation values. In PhaseII, upon administering CD-CAT.v2 on 210patients,22 items were removed having low correlation values (R<0.4) with SDE. Finally, a 13-item tool (CD-CAT.v3;α=0.84) was obtained with high criterion validity with SDE (r=0.806, p<0.001), moderate convergent validity with CDAT (r=0.602, p=0.007) and moderate to weak correlation with urine GIP (r=0.46, p=0.001) and IgA anti-tTG Ab (r=0.39, p=0.008), respectively. The final 13-item tool also strongly correlated with SDE (r=0.78, p<0.001) in an independent validation cohort of 70 CeD patients. Principal component analysis identified three relevant sub-scales with a cumulative-variance of 62%. The sensitivity and specificity of CD-CAT.v3 were 80% and 91%, respectively, with an area under curve of 0.905 with SDE. The obtained cut-off score of <19 from ROC-curve was further categorized as 13=excellent,14-18=very good, 19-28=average and >28=poor adherence to GFD. CONCLUSION: CD-CAT is a new and rapid tool for monitoring dietary adherence to GFD with high sensitivity and specificity which can be administered by both physicians and dietitians.