Faecal calprotectin: a noninvasive diagnostic tool and marker of severity in pouchitis

In pouchitis, the mucosa is infiltrated by activated polymorphonuclear neutrophils capable of producing calprotectin, a stable antimicrobial myelomonocytic protein.

The aim is to assess the ability of faecal calprotectin to differentiate between inflamed and noninflamed ileal pouches, and to correlate this with inflammation severity using the newly developed Objective Pouchitis Score.

Fifty-four stool samples were collected from patients who had undergone restorative proctocolectomy; 46 from patients with ulcerative colitis and eight from those with familial adenomatous polyposis coli. Faecal calprotectin concentrations were determined by quantitative enzyme-linked immunosorbant assay.

Of the ulcerative colitis patients, six were diagnosed with pouchitis and pre-pouch ileitis (median faecal calprotectin: 865 microg/g, with a range of 95-2350 microg/g); 13 had pouchitis alone (145, 33-3350 microg/g) and 27 were uninflamed (56, 4-705 microg/g). Of the familial adenomatous polyposis patients, one had pouchitis and pre-pouch ileitis (305 microg/g), and seven had noninflamed pouches (9, 6-26 microg/g). Stool samples obtained from pouchitis patients had significantly higher calprotectin concentrations compared with those obtained from uninflamed pouches (Mann-Whitney: P<0.0001). Faecal calprotectin concentrations correlated closely with the Objective Pouchitis Score, the Pouch Disease Activity Index and endoscopic and histological inflammatory scores (Spearman rank test: P values <0.0001). Using a faecal calprotectin threshold of >or=92.5 microg/g to define a positive result, Receiver Operating Characteristic analysis demonstrated a sensitivity of 90% and a specificity of 76.5%.

Faecal calprotectin measurement is a useful noninvasive tool in the diagnosis of acutely inflamed ileal pouches and correlates well with the severity of pouchitis.