P0694 DIAGNOSTIC VALUE OF ASCA AND ANCA IN PEDIATRIC GASTROENTINTESTINAL DISEASES

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Introduction: The anti-Saccharomyces Cerevisiae antibodies (ASCA) and the anti-neutrophil cytoplasmic antibodies (ANCA) are used as serological markers respectively for Crohn’s disease (CD) and ulcerative colitis (UC). Combined dosages yielded the best diagnostic value in adult patients but they were rarely studied in the pediatric population. Positive ASCA and/or ANCA were also found in other gastrointestinal diseases, namely celiac disease (CeD). The aim of this study was to reevaluate the diagnostic value of these markers in pediatric gastrointestinal diseases especially in inflammatory bowel diseases (IBD) and CeD. Methods: Sera of 73 patients (age:1–20 years) were studied: 25 IBD (17 CD and 8 UC), 22 CeD and 24 controls. ASCA and ANCA were qualitatively detected by indirect immunofluorescence (IIF) Results: We observed a statistically significant difference of ASCA prevalence between CD (47%) and CeD (9%-p<0.01) or controls (0%-p<0.001) but not between CD and UC (25%). On the other hand, there was a statistically significant difference of ANCA prevalence between UC (75%) and CD (11.7%-p<0.01), CeD (0%-p<0.001) or controls (0%-p<0.001). Positivity of one or both markers had a 68% sensitivity, 96% specificity and 85% positive predictive value (PPV) for the diagnosis of IBD. In the IBD group, the association of positive ASCA with negative ANCA had a 47% sensitivity, 88% specificity and 89% PPV for the diagnosis of CD. In the same group, the ANCA positivity associated to ASCA negativity had a 63% sensitivity, 88% specificity and 71% PPV for the diagnosis of UC. ASCA or ANCA positivity was not correlated to clinical aspects, localization or extension of the disease for CD and UC respectively (possibly due to the small size of the population). Conclusion: This study confirms the value of these serological markers, especially when used in combination, for the diagnosis of IBD in children. Unfortunately their low sensitivity does not allow using them as a screening test. On the other hand, these markers had no diagnostic value in CeD.