Serological markers in inflammatory bowel disease: the pros and cons

Aluminum as an adjuvant in Crohn's disease induction

Alum (AlK(SO(4))(2)) is an adjuvant commonly utilized in vaccines, and is a ubiquitous element used extensively in contemporary life. Food, air, water, waste, the earth's surface, and pharmaceuticals all represent pathways of aluminum (Al) exposure. Crohn's disease (CD) is a chronic relapsing intestinal inflammation in genetically susceptible individuals and is caused by yet unidentified environmental factors. Al is a potential factor for the induction of inflammation in CD, and its immune activities share many characteristics with the immune pathology of CD: many luminal bacterial or dietary compounds can be adsorbed to the metal surface and induce Th1 profile cytokines, shared cytokines/chemokines, co-stimulatory molecules, and intracellular pathways and stress-related molecular expression enhancement, affecting intestinal macrobiota, trans-mural granuloma formation, and colitis induction in an animal CD model. The inflammasome plays a central role in Al mode of action and in CD pathophysiology. It is suggested that Al adjuvant activity can fit between the aberrations of innate and adaptive immune responses occurring in CD. The CD mucosa is confronted with numerous inappropriate bacterial components adsorbed on the Al compound surface, constituting a pro-inflammatory supra-adjuvant. Al fits the diagnostic criteria of the newly described autoimmune/inflammatory syndrome induced by adjuvants. If a cause and effect relationship can be established, the consequences will greatly impact public health and CD prevention and management.

Clinical, endoscopic, and histological differentiations between Crohn's disease and intestinal tuberculosis

OBJECTIVES

The clinical, endoscopic, and histological features of Crohn's disease (CD) and intestinal tuberculosis mimic each other so much that it becomes difficult to differentiate between them. The aim was to find out clinical, endoscopic, and histological predictor features for differentiation between CD and intestinal tuberculosis.

METHODS

We recruited 106 patients, 53 each with CD and intestinal tuberculosis, in this study. The clinical, histological, and endoscopic features were subjected to univariate, bivariate, and multivariate analyses. On the basis of regression coefficients of the final multivariate logistic model, a score to discriminate between CD and intestinal tuberculosis was devised. For the validation of the score, the same model was tested on 20 new patients, each with CD and intestinal tuberculosis.

RESULTS

On univariate analysis, although longer duration of disease, chronic diarrhea, blood in stool, perianal disease, extra-intestinal manifestations, involvement of left colon, skip lesions, aphthous ulcers, cobblestoning, longitudinal ulcers, focally enhanced colitis, and microgranulomas were significantly more common in CD, partial intestinal obstruction, constipation, presence of nodular lesions, higher number, and larger granulomas were significantly more common in intestinal tuberculosis. On multivariate analysis, blood in stool (odds ratio (OR) 0.1 (confidence interval (CI) 0.04-0.5)), weight loss (OR 9.8 (CI 2.2-43.9)), histologically focally enhanced colitis (OR 0.1 (CI 0.03-0.5)), and involvement of sigmoid colon (OR 0.07(0.01-0.3)) were independent predictors of intestinal tuberculosis. On the basis of regression coefficients of the final multivariate logistic model, a score that varied from 0.3 to 9.3 was devised. Higher score predicted more likelihood of intestinal tuberculosis. Once the cutoff was set at 5.1, then the sensitivity, specificity, and ability to correctly classify the two diseases were 83.0, 79.2, and 81.1%, respectively. Area under the curve for receiver-operating characteristic (ROC) to assess the ability of these features to discriminate between CD and intestinal tuberculosis was 0.9089. The area under ROC in the validation data set was 89.2% (95% CI 0.79-0.99). With a similar cutoff score of 5.1, sensitivity and specificity in the validation model were 90% (95% CI 66.9-98.2) and 60% (95% CI 36.4-80.0), respectively.

CONCLUSIONS

Blood in stool, weight loss, focally enhanced colitis, and involvement of the sigmoid colon were the most important features in differentiating CD from intestinal tuberculosis.

Diagnostic role and clinical correlates of anti-Saccharomyces cerevisiae antibodies (ASCA) and anti-neutrophil cytoplasmic antibodies (p-ANCA) in Italian patients with inflammatory bowel diseases

BACKGROUND

Anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) are serological markers associated, respectively, with Crohn's disease and ulcerative colitis, whose clinical significance and possible diagnostic role are still poorly defined.

AIMS

(a) To evaluate the sensitivity, specificity and predictive values of isolated and combined ASCA and p-ANCA assays in a large cohort of Italian patients with inflammatory bowel disease (IBD) and (b) to assess whether their presence is associated with particular clinical features of the disease.

PATIENTS AND METHODS

Hundred and forty-six IBD patients (93 with Crohn's disease and 53 with ulcerative colitis) and 54 control patients were enrolled in the study. ASCA (IgA and IgG) and p-ANCA were determined by means of enzyme-linked immunosorbent assay and indirect immunofluorescence, respectively.

RESULTS

The specificities were excellent for both tests (ASCA in Crohn's disease, 98.1% both for IgA and IgG, and p-ANCA in ulcerative colitis, 92.5%); however, the sensitivities of both tests were low (59.1% for ASCA IgA, 44.1% for ASCA IgG, 39.6% for p-ANCA). ASCA specificity and positive predictive value reached 100% when positivity for both IgA and IgG was present. No significant association was found between the presence of a specific serological marker and patients' clinical features.

CONCLUSIONS

This study confirms the low prevalence of p-ANCA observed in ulcerative colitis patients from the Mediterranean area. The low sensitivity of ASCA and p-ANCA, despite their rather high specificity, renders them of little value in the screening of the general population, where the prevalence of IBD is low. However, in our series, a double positivity for ASCA IgA and IgG identifies with certainty the presence of Crohn's disease.