The anti-Saccharomyces cerevisiae antibody assay in a province-wide practice: Accurate in identifying cases of Crohn's disease and predicting inflammatory disease
To determine the utility of the anti-Saccharomyces cerevisiae antibody (ASCA) ELISA test developed in Manitoba in 2001 in a population-wide sample referred from physicians across Manitoba in their investigation of patients with gastrointestinal symptoms.
Patients whose serum was referred for ASCA testing in 2001 and 2002 were eligible for the present study. ELISA was performed by a technologist, blind to patient diagnoses. A single investigator contacted physicians to facilitate chart review. Data collected included demographics, final diagnoses and tests used to substantiate the final diagnosis.
Of 482 subjects identified, 410 charts were available for review and 29 of those were unavailable for follow-up or had incomplete charts. The present study population included Crohn's disease (CD, n=114), ulcerative colitis (n=74), indeterminate colitis (n=31), celiac disease (n=9), irritable bowel syndrome (n=75), other diagnoses (n=33) and no disease (n=45). ASCA had a sensitivity of 37% (95% CI 27.8 to 46.8) and specificity of 97% (95% CI 93.8 to 98.6) for diagnosing CD and an odds ratio for a diagnosis of CD of 18.4 (95% CI 8.2 to 41.3). The 47 ASCA-positive patients included the following diagnoses: CD=39, ulcerative colitis=3, indeterminate colitis=1, celiac disease=3 and no disease=1. The likelihood of having an inflammatory disease if ASCA is positive was nearly 40-fold.
A positive ASCA test using this assay nearly clinches a diagnosis of some form of inflammatory intestinal disease, which is highly likely to be CD. In symptomatic patients, a positive ASCA test should encourage the clinician to pursue further investigations.
Available from: Vasilis A Constantinides
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ABSTRACT: The aim of this study was to assess the diagnostic precision of antiSaccharomyces cerevisiae (ASCA) and perinuclear antineutrophil cytoplasmic antibodies (pANCA) in inflammatory bowel disease (IBD) and evaluate their discriminative ability between ulcerative colitis (UC) and Crohn's disease (CD).
Meta-analysis of studies reporting on ASCA and pANCA in IBD was performed. Sensitivity, specificity, and likelihood ratios (LR+, LR-) were calculated for different test combinations for CD, UC, and for IBD compared with controls. Meta-regression was used to analyze the effect of age, DNAse, colonic CD, and assay type.
Sixty studies comprising 3,841 UC and 4,019 CD patients were included. The ASCA+ with pANCA- test offered the best sensitivity for CD (54.6%) with 92.8% specificity and an area under the ROC (receiver operating characteristic) curve (AUC) of 0.85 (LR+ = 6.5, LR- = 0.5). Sensitivity and specificity of pANCA+ tests for UC were 55.3% and 88.5%, respectively (AUC of 0.82; LR+ = 4.5, LR- = 0.5). Sensitivity and specificity were improved to 70.3% and 93.4% in a pediatric subgroup when combined with an ASCA- test. Meta-regression analysis showed decreased diagnostic precision of ASCA for isolated colonic CD (RDOR = 0.3).
ASCA and pANCA testing are specific but not sensitive for CD and UC. It may be particularly useful for differentiating between CD and UC in the pediatric population.
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ABSTRACT: Advances in serologic markers, endoscopy, and radiology have led to rapid expansion of diagnosis and disease activity assessment of inflammatory bowel disease (IBD). Serologic markers may have diagnostic value in patients with an intermediate pretest probability of IBD, but these serology tests lack complete sensitivity, and a negative serology result does not exclude the possibility of IBD. Several recent studies have confirmed the utility of serologies in predicting intestinal complications and need for surgery in Crohn's disease. Serum C-reactive protein concentrations correlate with clinical, endoscopic, and radiologic measures of disease activity and appear to have prognostic value in acute severe colitis. Capsule and double balloon endoscopy allow visual inspection of previously inaccessible areas of the small intestine and are useful for patients with suspected small bowel involvement but negative results on conventional testing. CT enterography, which entails oral ingestion of a large volume of a neutral or negative contrast agent and scanning that highlights differences in contrast between the lumen and the bowel wall, appears to be more sensitive than small bowel follow-through for detecting small bowel Crohn's disease and provides extraluminal information. Magnetic resonance enterography uses principles similar to those for CT enterography, and early results are encouraging.
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ABSTRACT: Advances in serologic markers and imaging modalities continue to revolutionize diagnostic approaches to inflammatory bowel disease (IBD). Autoimmune and antimicrobial antibodies demonstrate diagnostic value in those patients with a moderate pretest probability of disease. Emerging data also support the use of antimicrobial antibody levels as a predictive tool for small bowel complications and the need for future surgery. In addition to being a prognostic marker in patients with acute severe colitis, serum C-reactive protein has been shown to correlate with clinical, endoscopic, and radiologic measures of disease activity. Capsule endoscopy and double-balloon endoscopy allow for visualization of the entire small bowel, and double-balloon endoscopy also has the capability to treat lesions. CT enterography is beginning to replace small bowel follow-through because of its high sensitivity and specificity for disease of the small intestine. Both CT and magnetic resonance enterography detect luminal and extraluminal abnormalities, with MRI serving as a safe imaging option in cases of pregnancy and renal insufficiency. These newer modalities add to the armamentarium clinicians can use for evaluation of IBD.
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