SHORT-TERM RESPONSIVENESS OF THE PEDIATRIC CROHN'S DISEASE ACTIVITY INDEX

JN Critch, PS Kundhal, M Zachos, AM Griffiths

Division of Gastroenterology/Nutrition, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario

BACKGROUND/AIM: The Pediatric Crohn’s Disease Activity Index (PCDAI) is a reliable and validated multi-item measure, which, in comparison to the adult CDAI more accurately classifies disease activity among children and adolescents. Inclusion of linear growth velocity as a variable in the PCDAI has raised concerns about its responsiveness to change in the setting of an acute treatment trial. Moreover, there are no PCDAI data available by which to define short-term clinical response. In preparation for use in clinical trials, we evaluated PCDAI responsiveness and assessed the clinical significance of short-term changes in PCDAI values.

METHODS: Children and adolescents being evaluated for active Crohn’s disease warranting initiation of a new therapy were eligible for the study. PCDAI and physician global assessment of disease activity were recorded at baseline and at follow-up visit 3-8 weeks later. Standardized effect size (SES) and standardized response mean (SRM) were calculated as measures of responsiveness. Change in PCDAI at follow-up was compared to physician global assessment of change (on a Likert scale). Receiver operating characteristic (ROC) curves were constructed to determine the minimal PCDAI score change for significant clinical improvement.

RESULTS: 25 pediatric patients (16 males, 9 females) aged 13.2 +/- 3.2 years (range 7.0 - 17.3 years) were evaluated at baseline and after an interval of 32.7 +/- 9.9 days (range 20 - 55 days). The SES and SRM for the PCDAI were 1.11 and 0.76 respectively. The discriminative ability (area under the curve) of the PCDAI for detecting at least a moderate improvement in disease activity was 0.965 (95% confidence interval 0.904 - 1.000, p<0.001). The optimal cutoff for significant clinical improvement was determined to be a change in PCDAI of -12.5 (sensitivity 83.3%, specificity 92.3%).

CONCLUSIONS: The PCDAI is responsive to improvement in disease activity in Crohn’s disease patients over a short interval. The PCDAI is an appropriate instrument to use in pediatric acute treatment trials.

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