Faecal haemoglobin concentration is related to detection of advanced colorectal neoplasia in the next screening round.

Objective: To examine associations between faecal haemoglobin concentrations below the cut-off used in colorectal cancer screening and outcomes in the next screening round. Methods: In the Scottish Bowel Screening Programme, faecal haemoglobin concentrations and diagnostic outcomes were investigated for participants with a negative result (faecal haemoglobin concentrations< 80.0 mg Hb/g faeces), followed by a positive result within two years. Results: Of 37,780 participants with negative results, at the next screening round, 556 (1.5%) screened positive and 30,293 (80.2%) negative. Initial median faecal haemoglobin concentrations (2.1 mg Hb/g faeces, IQR: 0.0-13.2) were higher in those with subsequent positive results than those with subsequent negative results (0.0 mg Hb/g faeces, IQR: 0.0-1.4; p< 0.0001). Using faecal haemoglobin concentrations 0.0-19.9 mg Hb/g faeces as reference, logistic regression analysis showed high adjusted odds ratios for advanced neoplasia (advanced neoplasia: colorectal cancer or higher risk adenoma) detection at the next round of 14.3 (95% CI: 8.9-23.1) in those with initial faecal haemoglobin concentrations 20.0-39.9 mg Hb/g faeces, and 38.0 (95% CI: 20.2-71.2) with 60.0-79.9 mg Hb/g faeces. Conclusions: A higher proportion of participants with faecal haemoglobin concentrations of520 mg Hb/g faeces had advanced neoplasia detected at the next round than participants with lower faecal haemoglobin concentrations. Although most relevant when using high faecal haemoglobin concentrations cut-offs, studies of faecal haemoglobin concentrations and outcomes over screening rounds may provide strategies to direct available colonoscopy towards those at highest risk.