Background/aim: Existing measures of ulcerative colitis (UC) activity are generally not a product of rigorous development and were not developed for pediatric use. Our aim: to develop and validate a non-invasive, multi-item measure of UC activity for use in pediatric clinical trials. Methods: A judgmental approach was used for item generation using a Delphi group of 48 experts in pediatric IBD and a thorough literature review. Further item reduction and item weighting was performed by regression analysis using a prospective cohort of pediatric UC patients from 5 IBD centers. Physician global assessment of the disease activity (PGA) was used as the dependent variable and the PUCAI items as the predictors. The β estimates of the model served to guide the weighting, governed by maximizing R2 and aided by a correlation matrix. Reliability was assessed by Intra-Class Correlation coefficient (ICC) using two way random ANOVA. Validation of the weighted PUCAI was performed on a separate prospective cohort of UC children undergoing colonoscopy. Colonoscopic appearance and PGA served as the constructs. PUCAI was also simultaneously compared with a common invasive adult index (UCDAI; mayo clinic score). Sample size calculation was based on 10 patients/df of the weighting model (n=160) and further 30 for the correlation validity. Results: A list of 41 potential items was generated by the expert panel. Rank order was considered in item reduction, following 4 rounds of feedback to the group. Gradations for the 11 highest ranking items were selected by consensus following much iteration. The draft PUCAI was completed independently by two physicians assessing 157 children with UC (age 12.7 ± 3.8 yr, 52% males; 77% extensive; 34% moderate to severe; 19% mild and 47% quiescent). ROC curves confirmed the validity of the gradations. Reliability was excellent (ICC>0.9 for all included items). Eight items were most important in the regression analysis: stool number, consistency and blood, abdominal pain, activity level, nocturnal diarrhea, albumin and CRP. In the validation set, the weighted index was highly correlated with both PGA (r=0.86, p<0.001) and colonoscopic appearance (r=0.77, p<0.001), higher than two commonly used, non-invasive adult indices, calculated simultaneously (Lichtiger (r=0.65) and Seo index (r=0.66)). The PUCAI also showed excellent correlation (r=0.92, p<0.001) with the reference invasive index (mayo-score). The laboratory items, improved the PUCAI performance, but not significantly. Conclusions: The rigorously developed PUCAI has excellent reliability and validity. It provides a non-invasive measure of disease activity for use in pediatric clinical trials.
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Turner et al. (2006) studied this question.