A service evaluation of the use of faecal immunochemical tests in symptomatic patients aged under 50 years presenting to primary care.

Background: Most colorectal cancers (CRCs) occur in individuals aged over 50 years; however, the incidence in younger age groups is increasing. Diagnosis in younger patients is frequently delayed due to non-specific symptoms and the relative frequency of benign disease. There is a need to identify patients who warrant further investigation for CRC. This study reviewed whether a faecal haemoglobin (f-Hb) ≥10 μg Hb/g faeces measured by the faecal immunochemical test for f-Hb (FIT) was associated with CRC in a local primary care population aged under 50 years.

Methods: f-Hb results from symptomatic patients aged 18-49 years presenting to primary care during a 17-month period were extracted from local laboratory information systems. Colonoscopy lists were obtained from three local trusts. The Somerset Cancer Registry was searched to identify CRCs. f-Hb and outcomes were matched using NHS numbers.

Results: A total of 3119 patients were included (median age 41 years); 313 of 2682 patients with f-Hb <10 μg/g (11.7%) and 305 of 437 patients with f-Hb ≥10 μg/g (69.8%) underwent colonoscopy. Twelve CRCs were detected. At a cut-off of 10 μg/g, the positivity rate was 14.0%, sensitivity was 100% (75.8-100%), specificity was 86.3% (85.1-87.5%), positive predictive value (PPV) was 2.7% (2.5-3.0%) and negative predictive value (NPV) was 100%. At a cut-off of 150 μg/g, sensitivity was 83.3% (55.2-95.3%), specificity was 95.2% (94.4-95.9%), PPV was 6.2% (4.7-8.2%) and NPV was 99.9% (99.8-100%).

Conclusion: Our data supports the use of FIT to triage patients aged under 50 years presenting to primary care with symptoms suggestive of CRCs.