Abstract Background Faecal calprotectin (FC) is widely used as a non-invasive biomarker of intestinal inflammation in ulcerative colitis, demonstrating good correlation with endoscopic and histological activity in extensive disease. However, its usefulness in patients with isolated ulcerative proctitis remains uncertain. This study aimed to evaluate the association between FC and clinical, endoscopic, and histological activity in ulcerative proctitis. Methods A prospective study was conducted in adult patients with ulcerative proctitis. All participants provided a stool sample for FC measurement prior to flexible sigmoidoscopy with biopsies. Clinical, endoscopic, and histological disease activity were assessed using the partial Mayo score (PMS), the Mayo endoscopic subscore (MES), and the Nancy index (NI), respectively. Correlations between FC and disease activity were analysed using Spearman’s rank correlation. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic accuracy of FC. Results FC measurements and findings from 50 proctosigmoidoscopies were analysed. No significant correlation was observed between FC and PMS (r = 0.205; p = 0.153) or MES (r = 0.237; p = 0.098). FC levels were significantly associated with disease histological activity according to the NI (r = 0.312; p = 0.028). ROC analysis identified an optimal cut-off of 61 µg/g (sensitivity 43%, specificity 90%) for predicting endoscopic activity. Conclusion Faecal calprotectin does not reliably reflect clinical or endoscopic activity in ulcerative proctitis. Although a weak but significant association with histological inflammation was identified, the overall accuracy of FC for predicting endoscopic activity was poor. FC should therefore be interpreted with caution in this setting and cannot replace endoscopic evaluation in patients with ulcerative proctitis. Reference: Maaser C, Sturm A, Vavricka SR, et al. ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 1: Initial diagnosis, monitoring of known IBD, detection of complications. J Crohns Colitis. 2019;13(2):144-164. doi:10.1093/ecco-jcc/jjy113 Conflict of interest: Pacheco, Tatiana: Monteiro, Sara: No conflict of interest Barros, Ana Rita: No conflict of interest Ramos, Diana: No conflict of interest Moura Costa, Juliana: No conflict of interest Barros, Luísa: No conflict of interest Silva, Jorge: No conflict of interest
Pacheco et al. (Thu,) studied this question.