Faecal immunochemical testing for adults with symptoms of colorectal cancer attending English primary care: a retrospective cohort study of 14 487 consecutive test requests

Abstract

Summary Background Faecal immunochemical testing (FIT) is recommended by the National Institute for Health and Care Excellence (NICE) to triage symptomatic primary care patients for further investigation of colorectal cancer. Aim To ascertain the diagnostic performance of FIT in symptomatic adult primary care patients. Methods Faecal samples from routine primary care practice in Oxfordshire, UK were analysed using the HM‐JACKarc FIT method between March 2017 and March 2020. Clinical details were recorded. Patients were followed for up to 36 months in linked hospital records for evidence of benign and serious (colorectal cancer, high‐risk adenomas and bowel inflammation) colorectal disease. The diagnostic accuracy of FIT is reported by gender, age group and FIT threshold. Results In 9896 adult patients with at least 6‐month follow‐up, a FIT result ≥10 µg Hb/g faeces had a sensitivity for colorectal cancer of 90.5% (95% CI 84.9%‐96.1%), specificity 91.3% (90.8%‐91.9%), positive predictive value (PPV) 10.1% (8.15%‐12.0%) and negative predictive value (NPV) 99.9% (99.8%‐100.0%). The PPV and specificity for serious colorectal disease were higher and the sensitivity and NPV lower than for colorectal cancer alone. The area under the curve for all adults did not change substantially by gender or by increasing the minimum age of testing. Using ≥10 µg Hb/g faeces, 10% of adults would be investigated to detect 91% of cancers, a number needed to scope of ten to detect one cancer. Using ≥7, ≥50 and ≥150 µg Hb/g faeces, 11%, 4% and 3% of adults would be investigated, and 91%, 74% and 54% cancers detected, respectively. Conclusion A FIT threshold of ≥10 µg Hb/g faeces would be appropriate to triage adult patients presenting to primary care with symptoms of serious colorectal disease. FIT may be used to reprioritise patients referred with colorectal cancer symptoms whose investigations have been delayed by the COVID‐19 pandemic.

A risk-stratified approach to colorectal cancer prevention and diagnosis

“…In symptomatic patients, a primary care study in the UK reported a sensitivity and specificity of 91% for CRC for a FIT result ≥10 μg/g (ref. 39 ). In this respect, FIT can be considered as the first quantitative laboratory biomarker in use for CRC risk stratification.…”

Letter: extending FIT from DG30 to NG12 patients. Letter: faecal immunochemical testing for adults with symptoms of colorectal cancer – ready for prime time? Authors' reply: a unified approach to safety netting negative FITs is required

“…The authors' declarations of personal and financial interests are unchanged from those in the original article. 4 Brian Shine 4…”

“…We presented evidence from a symptomatic cohort, tested in primary care in the context of NICE DG30 guidance. 4 Turvill rightly cautions against extrapolating estimates of risk associated with positive or negative test results from one population to another with a different disease prevalence. He illustrates this by comparing our 'lowrisk' symptomatic primary care population (DG30) with the 'high-risk' symptomatic referred population (NG12).…”

Letter: extending FIT from DG30 to NG12 patients

“…Perhaps because of this, there was relatively little co‐ordinated data collection for patient outcomes when FIT was introduced in this setting. The excellent paper by Nicholson et al is, therefore, extremely welcome 1 . Because of its high specificity, FIT has proven effective in identifying over 90% of patients with colorectal cancer among a cohort of people who would not ordinarily be referred with suspected colorectal cancer, without generating large numbers of unnecessary additional colonoscopies.…”