Faecal immunochemical testing (FIT) in primary care: a follow-up service evaluation

Area of Science:

• Gastroenterology
• Oncology
• Public Health

Background:

• Colorectal cancer (CRC) is a significant health concern in the UK.
• National Institute for Health and Care Excellence (NICE) guidelines recommend faecal immunochemical testing (FIT) for CRC detection.
• A FIT service measuring faecal haemoglobin (f-Hb) was implemented for symptomatic patients.

Purpose of the Study:

• To re-examine the utilization and diagnostic performance of FIT in symptomatic patients over two successive 6-month periods (April-September 2020 and 2021).
• To evaluate the impact of FIT implementation on urgent lower gastrointestinal cancer referrals and outcomes.

Main Methods:

• Retrospective analysis of FIT requests and laboratory data for patients in April-September 2020 and 2021.
• Matching laboratory results with clinical outcomes of patients referred via the urgent lower gastrointestinal cancer pathway.
• Reporting on patient demographics, referral reasons, clinical outcomes, and diagnostic test performance.

Main Results:

• In 2020, 4042 samples yielded 57 CRCs; in 2021, 10,508 samples yielded 65 CRCs.
• The proportion of samples from patients under 50 increased from 27.7% in 2020 to 32.8% in 2021.
• FIT sensitivity for CRC at ≥10 µg/g was high (92.9% in 2020, 96.9% in 2021), but specificity was low (46.6% in 2020, 29.9% in 2021).

Conclusions:

• The specificity of FIT at a 10 µg/g cut-off in primary care in North East London is lower than reported in other studies.
• The low specificity may lead to an increased burden on colorectal services due to a higher number of false positives.
• Further consideration is needed regarding the optimal use and interpretation of FIT results in this population.