Combining f-Hb, Age, and Iron-Deficiency Anaemia Improves CRC Risk Stratification in Primary Care
A large retrospective study published in Gut, has demonstrated that combining faecal haemoglobin (f-Hb) concentration, patient age, and iron-deficiency anaemia (IDA) status significantly enhances risk prediction for colorectal cancer (CRC) in symptomatic patients.
The study evaluated 34,647 symptomatic patients who submitted contemporaneous f-Hb and full blood count samples between December 2015 and December 2019. Using record linkage to the Scottish Cancer Registry, the investigators identified 571 incident CRC cases and stratified risk by f-Hb concentration, age, and IDA presence.
Key findings support refinement of current referral thresholds. “The risk of CRC breached 3% in patients with f-Hb >99 µg Hb/g aged >40 years,” the authors reported. Notably, the risk reached 30% (95% CI, 19.4–41.0) among patients aged >55 years with f-Hb >99 µg Hb/g and concurrent IDA.
Importantly, among 2,029 patients with f-Hb in the 10–19 µg Hb/g range, only 1.3% had CRC. In this subgroup, “CRC risk did not exceed 3% in patients <85 years and no IDA,” suggesting a potential opportunity to reduce unnecessary urgent referrals for colonoscopy in low-risk individuals.
Overall, 22.8% of patients had f-Hb ≥10 µg Hb/g, the current threshold for urgent referral under National Institute for Health and Care Excellence (NICE) guidance. However, the study suggests that age and IDA status should be considered alongside f-Hb to better discriminate risk.
“Combining f-Hb, patient age and IDA status improves CRC risk prediction,” the authors concluded. This approach may allow clinicians to more confidently identify patients at low risk—specifically, those with f-Hb <20 µg Hb/g and no IDA—potentially reducing invasive investigations without compromising diagnostic safety.
These findings offer a data-driven framework to refine existing guidelines and enhance the efficiency of CRC workup in primary care.
Reference
Digby J, Nobes J, Strachan JA, et al. Combining faecal haemoglobin, iron deficiency anaemia status and age can improve colorectal cancer risk prediction in patients attending primary care with bowel symptoms: a retrospective observational study. Gut. March 2025:gutjnl-334248. doi:10.1136/gutjnl-2024-334248
