Quantitative faecal immunochemical testing to guide colorectal cancer pathway referral in primary care

Hidden blood in faeces

2.1 Colorectal cancer may be associated with a variety of symptoms including blood in faeces. Small amounts of hidden blood in faeces (known as faecal occult blood) can show that there is bleeding from the gastrointestinal tract, potentially from malignant (cancerous) growths on the inner lining of the large intestine. Several other conditions (such as inflammatory bowel disease) may also cause blood in faeces.

2.2 Faecal immunochemical testing (FIT) detects small amounts of blood in a faecal sample using antibodies specific to human haemoglobin. A positive FIT result alone cannot confirm a diagnosis of colorectal cancer. Further assessment using colonoscopy or CT colonography is needed to confirm diagnosis.

Care pathway and clinical need

2.3 NICE's guideline on suspected cancer (NG12) and NICE's diagnostics guidance on quantitative FIT to guide referral for colorectal cancer in primary care (DG30) recommend:

2.4 People referred to secondary care typically have further investigation using colonoscopy, or sometimes CT colonography. Clinicians have observed that many people on the suspected colorectal cancer referral pathway do not have any unusual findings at colonoscopy. So, using FIT could mean that people who are unlikely to have colorectal cancer may avoid colonoscopy, and that people who are more likely to have colorectal cancer can be prioritised more effectively. Colonoscopy capacity is limited, and there are sometimes long wait times. Using FIT could reduce the number of people referred for colonoscopy, and so reduce the waiting times for people on non-urgent referral pathways.

2.5 In 2022, the Association of Coloproctology of Great Britain & Ireland (ACPGBI) and the British Society of Gastroenterology (BSG) published guidance on FIT in patients with signs or symptoms of suspected colorectal cancer. This recommended using:

FOB Gold (Sentinel/Sysmex)

2.9 FOB Gold is an automated quantitative immunoturbidimetric FIT system. It comprises faecal sample collection tubes that collect 10 milligrams of faeces in 1.7 ml of buffer, and latex agglutination reagent. FOB Gold is compatible with Sentinel's own SENTiFIT series of analysers and analysers manufactured by 5 other companies. The performance characteristics of the assay and throughput of the test vary depending on which analyser is used. The SENTiFIT 270 can run 270 samples per hour.

HM-JACKarc (Minaris Medical/Alpha Laboratories)

2.10 HM‑JACKarc is an automated quantitative immunoturbidimetric FIT system. It comprises a sample collection device, designed to measure 2 milligrams of faeces in 2 ml of buffer, latex agglutination reagent, and buffer solution. The assay is compatible with the HM‑JACKarc analyser, which can process up to 200 samples per hour, with a maximum capacity of 80 samples per run.

IDK TurbiFIT (Immundiagnostik)

2.11 IDK TurbiFIT is an immunoturbidimetric FIT assay compatible with a range of automated analysers from 16 manufacturers. The TurbiFIT kit comprises reagents, control samples and calibration samples. IDK TurbiTUBE sample collection devices are available separately, and collect 15 milligrams of faeces in 1.5 ml of buffer. The performance characteristics and throughput of the assay vary depending on which analyser is used.

IDK hemoglobin and hemoglobin/haptoglobin complex ELISA tests (Immundiagnostik)

2.12 The IDK hemoglobin ELISA comprises:

2.13 The company also produces the IDK hemoglobin/haptoglobin complex ELISA, which is similar but uses a microtiter plate pre-coated with anti-haptoglobin antibodies.

NS-Prime (Alfresa/Abbott)

2.14 NS‑Prime is an automated quantitative immunoturbidimetric FIT system. It comprises a specimen collection container that collects 10 milligrams of faeces in 1.9 ml of buffer. The test is run on the NS‑Prime analyser. The NS‑Prime haemoglobin reagent is specific to the NS‑Prime analyser and cannot be used on other platforms. The NS‑Prime analyser can process 300 tests per hour with a maximum capacity of 220 samples per run.

OC-Sensor (Eiken Chemical/MAST Diagnostics)

2.15 OC‑Sensor is a quantitative immunoturbidimetric FIT. It comprises faecal sample collection tubes, latex agglutination reagent and buffer. The OCAuto sampling bottles can hold 10 milligrams of faeces. The test can be run on either the OC‑Sensor PLEDIA or OC‑Sensor iO analysers, which differ in the number of samples they are able to process. Two other historical OC‑Sensor devices (DIANA and MICRO) were also included in the assessment and assumed to be equivalent to the other OC‑Sensor devices.

2.16 The OC‑Sensor PLEDIA can process up to 320 samples per hour, with a maximum capacity of 200 samples per run. The OC‑Sensor iO can process up to 88 samples per hour with a maximum capacity of 20 samples per run. MAST Diagnostics state that the OC Sensor iO will be replaced by the OC‑Sensor CERES, which processes 90 samples per hour and has technical specifications equivalent to the OC‑Sensor PLEDIA.

QuikRead go iFOBT (Aidian)

2.17 The QuikRead go is a point-of-care analyser that can be used for a number of different diagnostic tests, including the immunochemical faecal occult blood test (iFOBT) which is an immunoturbidimetric test. The kits contain reagent capsules and buffer in prefilled cuvettes. Faecal sampling sets and control materials are supplied separately. A single sample of 10 milligrams of faeces can be run at a time, and the test takes less than 2 minutes to display the result.

Standard care according to NICE guidance

2.18 The comparator is standard care according to NG12 and DG30. This begins with clinical assessment of symptoms by a GP in primary care. DG30 recommends triaging people with 'low risk' symptoms using FIT and NG12 recommends immediately referring people with 'high risk' symptoms using a suspected cancer pathway referral.

Reference standard

2.19 The reference standards used for assessing the accuracy of FIT are colonoscopy, CT colonography or long-term follow up.