Background: The faecal immunochemical test (FIT) has proven utility for colorectal cancer detection in symptomatic patients. However, most patients with a raised faecal haemoglobin (f-Hb) do not have colorectal cancer. We investigated alternative diagnoses and demographics associated with a raised f-Hb in symptomatic patients.
Methods: A retrospective, observational study was performed of patients with FIT submitted between August 2018 to January 2019 in NHS Greater Glasgow and Clyde followed by colonoscopy. Colonoscopy/pathology reports were searched for alternative diagnoses. Covariables were compared using the χ2 test. Multivariate binary logistic regression identified independent predictors of a raised f-Hb.
Results: 1272 patients were included. In addition to colorectal cancer (odds ratio (OR), 9.27 (95% confidence interval (CI): 3.61-23.83; p < 0.001)), older age (OR, 1.52 (95% CI: 1.00-2.32; p = 0.05)), deprivation (OR, 1.54 (95% CI: 1.21-1.94; p < 0.001)), oral anticoagulants (OR, 1.78 (95% CI: 1.01-3.15; p = 0.046)), rectal bleeding (OR, 1.47 (95% CI: 1.15-1.88; p = 0.002)), advanced adenoma (OR, 7.52 (95% CI: 3.90-14.49; p < 0.001)), non-advanced polyps (OR, 1.78 (95% CI: 1.33-2.38; p < 0.001)) and inflammatory bowel disease (IBD) (OR, 4.19 (95% CI: 2.17-8.07; p < 0.001)) independently predicted raised f-Hb. Deprivation (Scottish Index of Multiple Deprivation (SIMD) 1-2: OR, 2.13 (95% CI: 1.38-3.29; p = 0.001)) independently predicted a raised f-Hb in patients with no pathology found at colonoscopy.
Conclusions: An elevated f-Hb is independently associated with older age, deprivation, anticoagulants, rectal bleeding, advanced adenoma, non-advanced polyps and IBD in symptomatic patients. Deprivation is associated with a raised f-Hb in the absence of pathology. This must be considered when utilising FIT in symptomatic patients.
Keywords: Faecal; cancer; colorectal; haemoglobin; immunochemical; symptomatic; test.