Authors (including presenting author) :
LY Mak (1), LJ Chen (2), SM Tong (2), KS Lau (2), WK Leung (2)
Affiliation :
(1) Department of Medicine, Queen Mary Hospital, (2) Department of Medicine, The University of Hong Kong
Introduction :
Lower abdominal symptoms, defined as lower abdominal pain or chronic diarrhea > 4 weeks, represent the majority of referral to gastroenterologists. Fecal calprotectin (FCT) and fecal occult blood test (FOB) are biomarkers which reflects gut neutrophilic inflammation and luminal hemorrhage, respectively.
Objectives :
We aimed to explore the role of these 2 biomarkers in identifying organic colorectal diseases in outpatients referred for lower abdominal symptoms.
Methodology :
Adult patients aged < 65 without known colorectal diseases and referred for lower abdominal symptoms were recruited. Stool samples were saved for FCT and FIT before first consultation with gastroenterologists. FCT was measured by a quantitative enzyme-linked immunosorbent assay, whereas FOB was performed by guaiac-based Hemoccult Sensa. Patients with positive FOB or raised FCT (> 50ug/g) were called back for earlier first consultation. Ileocolonoscopy was arranged for those with alarming symptoms, positive FOB or raised FCT. Receiver operating characteristic (ROC) analysis of FCT was performed to identify the best cut-off for identification of organic colorectal diseases.
Result & Outcome :
74 patients (age 48.514.3-year-old, M:F= 25:49) were recruited. The mean FCT was 8590ug/g. Thirty-two (43.2%) and 10 (13.5%) patients had raised FCT and positive FOB, respectively, and the time to first consultation was shortened from 210 to 160 days (p=0.078) and 199 to 97 days (p=0.002). Ileocolonoscopy was performed in 45 patients. Organic colorectal disease was identified in 10 patients: 2 inflammatory bowel disease, 7 colonic polyps, and 1 radiation proctitis. These patients were older (56.3 vs. 48.7-year-old, p=0.092), had higher FCT (146 vs. 70ug/g, p=0.008) and higher proportion of positive FOB (40% vs. 7.8%, p=0.02) compared to those without organic disease. ROC analysis of FCT revealed an area under ROC to be 0.688 (95% CI 0.495-0.881, p=0.061). The derived cut-off level of FCT by maximizing the Youden’s index was 100ug/g (sensitivity 60%, specificity 78.4%). Multivariate logistic regression identified FCT>100ug/g (OR 5.361, 95%CI 1.13-25.429, p=0.035) and positive FOB (OR 8.726, 95% CI 1.473-51.679, p=0.017) to be independent variables associated with organic colorectal disease. Combining elevated FCT (>100 ug/g) and positive FOB further improved the sensitivity and specificity to 80% and 98%, respectively. Combing FIT and FOB are useful in identifying patients with organic colorectal disease who presented with lower abdominal symptoms, and may be useful in selecting patients for further endoscopic workup.
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