Mathematical weighting of the pediatric Crohn's disease activity index (PCDAI) and comparison with its other short versions.

BACKGROUND: The Pediatric Crohn's Disease Activity Index (PCDAI) has become the standard outcome measure in pediatric Crohn's disease (CD) clinical research. Other versions have been proposed but without systematic evaluation. The aim was to assess validity and responsiveness of the abbreviated PCDAI (abbrPCDAI), short PCDAI (shPCDAI), and modified PCDAI (modPCDAI) as measures of disease activity and to compare these with a mathematically weighted version developed here (wPCDAI). METHODS: The raw data from four prospectively collected datasets were used, totaling 437 children with CD (including two clinical trials). Discriminant validity utilized physician global assessment of disease activity (PGA), and construct validity the correlation with PGA and laboratory results. Feasibility and face validity were ascertained by a survey of 33 experts in pediatric CD. RESULTS: The wPCDAI had better performance than the PCDAI in construct validity and responsiveness and it discriminated better between the disease activity categories (area under the receiver operator characteristic [ROC] 0.97; 95% confidence interval [CI]: 0.95-0.99). In comparison to the original PCDAI, the noninvasive versions (abbrPCDAI and shPCDAI) had lower face, construct, and discriminant validity but were judged to be significantly more feasible. The modPCDAI performed well in the construct validation but was consistently inferior in all other parameters. Cutoffs that correspond to remission, response, and gradations of disease activity were determined for each index. CONCLUSIONS: The newly weighted wPCDAI performed better than the original PCDAI and is more feasible. The noninvasive versions (shPCDAI and abbrPCDAI) are inferior to the full PCDAI, but when needed in retrospective studies either may be equally used.

Appraisal of the pediatric Crohn's disease activity index on four prospectively collected datasets: recommended cutoff values and clinimetric properties.

OBJECTIVES: The Pediatric Crohn's Disease Activity Index (PCDAI) is the outcome measure of choice in clinical trials of pediatric Crohn's disease. The aim of this study was to provide knowledge on its performance and accuracy of different cutoff scores. METHODS: Longitudinal data prospectively generated from four sources were used, including the REACH and budesonide trials, a North-American inflammatory bowel diseases (IBD) registry, and a cohort aimed at evaluating growth. Cutoff values of disease activity were determined by physician global assessment from the pooled cohort using serial receiver operator characteristic curves and area under the curve (AUC) as well as comparing the overall accuracy. Test-retest reliability and responsiveness were ascertained by comparing the baseline and follow-up scores, using an external anchor. RESULTS: A total of 437 children were included (268 (61%) males, mean age 12.9+/-2.6 years). To define remission, a composite definition of <10 points or <7.5 points without the height item had the highest accuracy; this addressed the limitation that height is not a responsive item. The best cutoff of 10-27.5 was determined for mild disease, 30-37.5 for moderate disease, 40-100 for severe disease, and a change of >12.5 points for response (AUC 0.8-0.9; P<0.001). Ninety children whose disease remained unchanged showed fair test-retest reliability (intraclass correlation coefficient=0.74-0.8; P<0.001). The PCDAI showed good responsiveness, as reflected from the correlational (r=0.7; P<0.001), distributional (Guyatt's responsiveness statistics=0.9), and diagnostic utility analysis (AUC 0.85 (95% confidence interval 0.81-0.88). CONCLUSIONS: The clinimetric properties of the PCDAI are sufficient to support its use in clinical research. Cutoff values suggested by this study differ slightly from those previously published on much smaller cohorts.