Discriminating IBD from IBS: comparison of the test performance of fecal markers, blood leukocytes, CRP, and IBD antibodies.

BACKGROUND Symptoms of inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) can overlap. We aimed to determine the accuracy of fecal markers, C-reactive protein (CRP), blood leukocytes, and antibody panels for discriminating IBD from IBS and to define a "best test." METHODS We prospectively included 64 patients with IBD (36 Crohn's disease [CD], 28 ulcerative colitis [UC]), 30 with IBS, and 42 healthy controls. Besides CRP and blood leukocytes, blinded fecal samples were measured for calprotectin (PhiCal Test, enzyme-linked immunosorbent assay [ELISA]), lactoferrin (IBD-SCAN, ELISA), Hexagon-OBTI (immunochromatographic test for detection of human hemoglobin), and LEUKO-TEST (lactoferrin latex-agglutination test). Blinded serum samples were measured for the antibodies ASCA (ELISA) and pANCA (immunofluorescence). RESULTS Overall accuracy of tests for discriminating IBD from IBS: IBD-SCAN 90%, PhiCal Test 89%, LEUKO-TEST 78%, Hexagon-OBTI 74%, CRP 73%, blood leukocytes 63%, CD antibodies (ASCA+/pANCA- or ASCA+/pANCA+) 55%, UC antibodies (pANCA+/ASCA-) 49%. ASCA and pANCA had an accuracy of 78% for detecting CD and 75% for detecting UC, respectively. The overall accuracy of IBD-SCAN and PhiCal Test combined with ASCA/pANCA for discriminating IBD from IBS was 92% and 91%, respectively. CONCLUSIONS The PhiCal Test and IBD-SCAN are highly accurate for discriminating IBD from IBS. There is only marginal additional diagnostic accuracy when the PhiCal Test and IBD-SCAN are combined with ASCA and pANCA. ASCA and pANCA have a high specificity for IBD.