No abstract

PCDAI scores accurately reflect disease activity as assessed by physician global assessment. A PCDAI score of > or = 30 has acceptable sensitivity and specificity to indicate disease of moderate/severe activity. A PCDAI decrease of 12.5 points or greater following therapeutic intervention accurately reflects a clinically significant response. The PCDAI is an appropriate tool for intervention trials in Crohn disease in children.

In previous studies of the antibody response to hepatitis B vaccine in 598 subjects who received a full course of vaccination, we observed a bimodal response, with about 14 percent producing less than approximately 1000 radioimmunoassay (RIA) units. An analysis of the major histocompatibility complex (MHC) HLA and complement types of 20 of the subjects with the lowest responses indicated a greater-than-expected number of homozygotes for the extended or fixed MHC haplotype [HLA-B8, SC01, DR3]. This finding suggested that the lack of a normal response was a recessive MHC-linked trait. In this study, we prospectively vaccinated five homozygotes and nine heterozygotes for this haplotype in the expectation that the homozygotes would produce much lower levels of antibody than the heterozygotes. When the antibody response was assessed two months after the third injection, four of the five homozygotes had produced very low levels (approximately 1000 units or less) of antibody (mean, 467 RIA units; range, less than 8 to 1266), whereas all nine heterozygotes produced more than 2500 RIA units (mean, 15,608; range, 2655 to 28,900) (P less than 0.01). We conclude that the usual response to hepatitis B surface antigen is due to the presence of a dominant immune-response gene in the MHC and that a low response is due to the absence of such a gene and the presence on both chromosomes of MHC haplotypes (such as [HLA-B8, SC01, DR3]) that indicate such a response.

OBJECTIVES The objectives of this study were prospective evaluation of MR enterographic accuracy for detecting Crohn's disease imaging features in pediatric patients compared with a CT reference standard, as well as determination of MR enterographic accuracy for detecting active bowel inflammation and fibrosis using a histologic reference standard. MATERIALS AND METHODS The study group for this blinded prospective study included 21 pediatric subjects with known Crohn's disease scheduled for clinical CT imaging and histological bowel sampling for symptomatic exacerbation. All subjects and their parents gave informed consent to also undergo MR enterography. CT and MR enterography examinations were independently reviewed by 2 radiologists and scored for Crohn's disease features. All bowel histology specimens were reviewed by a single pathologist for presence of active mucosal inflammation and mural fibrosis, followed by imaging-histological correlation. RESULTS All 21 subjects underwent MR enterography and histological sampling, 18 of whom also underwent CT. MR enterography demonstrated high sensitivity for detecting Crohn's imaging features (bowel wall thickening, mesenteric inflammation, lymphadenopathy, fistula, abscess) compared with CT, with individual sensitivity values ranging from 85.1-100%. Out of a total of 53 abnormal bowel segments with MRI-histology correlation, MR enterography demonstrated 86.7% accuracy (90.0% sensitivity, 82.6% specificity) for detecting active inflammation (P < 0.001). Accuracy of MR enterography for detecting mural fibrosis overall was 64.9% compared with histology, but increased to 88.2% (P < 0.05) for detecting fibrosis without superimposed active inflammation. CONCLUSIONS MR enterography can substitute for CT as the first-line imaging modality in pediatric Crohn's patients, based on its ability to detect intestinal pathology in both small and large bowel as well as extraintestinal disease manifestations. Additionally, MR enterography provides an accurate noninvasive assessment of Crohn's disease activity and mural fibrosis and can aid in formulating treatment strategies for symptomatic patients and assessing therapy response.