Beyond Histological Remission: Intramucosal Calprotectin as a Potential Predictor of Outcomes in Ulcerative Colitis

Histological remission and low faecal calprotectin are positive prognostic factors in ulcerative colitis [UC]. Intramucosal calprotectin [iMC], which can be readily determined by immunohistochemistry, has not so far been evaluated as a predictor of outcome in UC. We aimed to investigate the relationship between iMC and clinical, endoscopic, and histological measures of remission in UC, and the independent prognostic value of iMC.

Ambulant patients with UC were recruited for a study comparing clinical activity indices. Sigmoidoscopy and biopsy were performed at the index visit. Clinical, endoscopic, and histological activity were scored and iMC semi-quantitatively measured using immunohistochemistry for the S100A8/9 heterodimer on colonic biopsies, scored as the mean number of positive cells in five high-power fields [HPF]. At the end of follow-up [6 years], data on steroid use, hospitalisation, and colectomy ['adverse outcomes'] were collected.

iMC was determined in 83 patients and 20 controls, and correlated with clinical, endoscopic, and histological activity [r = 0.51, 0.65, 0.53, p > 0.001, respectively]. iMC was lowest (median 2.4, interquartile range [IQR]: 5.2-5, p < 0.001) in patients with concordance between clinical, endoscopic, and histological remission. Median iMC > 5/HPF was associated with adverse outcome (hazard ratio [HR] 3.36, confidence interval [CI] 1.58, 7.15, p < 0.001). Only 53%, 33%, and 25% of patients in histological remission with iMC > 5 cells/HPF avoided an adverse outcome after 1, 3, and 6 years, respectively.

iMC was lowest in patients with concordant clinical, endoscopic, and histological remission. Median iMC > 5/HPF was associated with adverse outcomes despite histological remission. Therefore iMC is a potentially useful independent marker of activity.