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

Abstract

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.