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

Abstract

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) ≥10μg 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. f-Hb results from symptomatic patients aged 18-49years 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. A total of 3119 patients were included (median age 41years); 313 of 2682 patients with f-Hb <10μg/g (11.7%) and 305 of 437 patients with f-Hb ≥10μg/g (69.8%) underwent colonoscopy. Twelve CRCs were detected. At a cut-off of 10μg/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 150μg/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%). Our data supports the use of FIT to triage patients aged under 50 years presenting to primary care with symptoms suggestive of CRCs.