P0421 Clinical validity of a seroproteomic index of endoscopic activity in pediatric Crohn’s disease

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Abstract Background A seroproteomic index (i.e. the serum index) corresponds to 13 protein markers, including CRP, combined as a multianalyte assay with a score range 0-100 where higher score is associated with higher probability of endoscopic activity in adult CD. We aimed to evaluate its performances in pediatric CD. Methods Children with CD were enrolled from two separate cohorts. Cohort 1 enrolled CD from multiple centers in the United States (n=118) and cohort 2, was multinational (n=160). A simple endoscopic score for CD (SESCD) was collected (<3 points indicate endoscopic healing) with a blood specimen. Clinical disease status was measured using the Harvey Bradshaw index (HBI, cohort 1) or pediatric CD activity index (PCDAI, cohort 2) (PCDAI<10 or HBI<5 indicate clinical remission). Fecal calprotectin (FC) was collected in 180 patients from both cohorts. Serum specimens were processed in Prometheus Laboratories, San Diego, CA. Statistical analysis consisted of linear regression analysis, calculation of receiver operating characteristics curves (ROC) with area under the curve (AUC), sensitivity, specificity, Odds ratio (OR). Results In the 278 enrolled children (median age 14 years [IQR: 12-16 years], 46% females), median SESCD was 5 points (IQR: 0-12 points, 63% with endoscopic active disease); median CRP was 2.5 mg/L (IQR: 0.3-8.4 mg/L), median FC was 592 µg/g (IQR: 135-1147 µg/g) and median serum index was 33 (IQR: 17-60 points). AUROC analysis yielded significantly better area under ROC curve (AUROC, 0.87±0.03) for FC than the serum index (0.78±0.04) and CRP (0.77±0.04) (p<0.05) in distinguishing endoscopic active disease from endoscopic healing. There was a 9-fold higher likelihood of endoscopic active disease with serum index above 32 points (OR= 8.95 [95%CI: 5.02,15.96] p<0.001) with 70% sensitivity and 79% specificity (PPV=85%; NPV=61% at 63% pretest) (Table). In multivariate analysis EHI above 32 points (aOR= 3.00 [95%CI: 1.25, 4.76] p=0.043), active clinical disease (aOR= 2.01 [95%CI: 0.85, 4.76] p=0.114), FC>250 µg/g (aOR= 5.61 [95%CI: 2.4,13.09] p<0.01) and CRP above 3 mg/L (aOR=2.09 [95%CI: 0.9-4.85])(p=0.08) associated with active endoscopic disease) (Figure). In the subset with clinical remission (n=158), or CRP below 3 mg/L (n=136), or FC levels below 250 µg/g (n=116), EHI above 32 points was still associated with higher likelihood of endoscopic disease (OR=5.4 [95%CI: 2.6,11.1], OR= 6.8 [95%CI: 2.9,15.8], and OR=4.0 [95%CI: 1.3,12.8], respectively) (p<0.05) (Figure). Conclusion These data support the association of the serum index with endoscopic outcome in pediatric CD patients.