Faecal Immunochemical Test (FIT) can be used for early recognition of colorectal (bowel) cancer.

FIT for colorectal cancer investigations

Colorectal (bowel) Cancer is the fourth most common cancer in the UK. It effects both men and women with the estimated lifetime risk of being diagnosed with bowel cancer being 1 in 15 men and 1 in 19 women. Mainly effecting older people, 94% of new cases are diagnoses in people over the age of 50.

More than 90% of colorectal cancer cases are treatable and curable if detected early, but still there are more than 15,000 deaths per year. It is the second most common cause of cancer death in the UK accounting for 10% of all cancer deaths. (Statistics from Cancer Research UK and Bowel Cancer UK)

Early detection of colorectal cancer, cancerous lesions or advanced adenomas is critical in order to administer treatment and significantly improve patient prognosis.

The purpose of FIT is to identify patients who may have adverse bowel pathology indicating a risk of having or developing colorectal cancer. In the case of diseases that involve hemorrhagic lesions in the gut, such as intestinal tumours or their precursors, the quantity of haemoglobin in stool is increased. Therefore determining the quantity of haemoglobin in the stool represents and effective screening method for the early detection of colorectal cancer.

An abnormal FIT result suggests that there may be bleeding in the lower gastrointestinal tract that requires further investigation, usually by colonoscopy of CT colonoscopy.

FIT is an immunochemical test for the detection of human haemoglobin (blood) in stool samples.

Quantitative or Qualitative FIT

Faecal Immunochemical Tests (FIT) are able to detect and quantify, with the aid of specific antibodies, the presence of human haemoglobin in a stool sample. Thereby, allowing you to distinguish between quantitative and qualitative FIT.

Quantitative FIT

Quantitative FIT tests offer an automated, quality-assured and precise evaluation under standardised conditions in a medical laboratory. Interpretation is objective and thereby rules out misinterpretations.

The “European Guidelines for Quality Assurance in Colorectal Cancer Screening” recommend quantitative FIT as the first choice for population-wide early detection of colorectal cancer because:

 

  • FIT offers greater sensitivity and specificity than gFOBT
  • Quantitative FIT tests are automated: for optimum standardisation/quality assurance
  • In the case of quantitative FIT the cut-off score (borderline score) can be adjusted
  • Immunoturbidimetric analysis requires dedicated analysers established in clinical laboratories

Qualitative FIT

Analysis of rapid qualitative tests can be performed in the laboratory of the GP practice. However, the visual interpretation of results by a colour change reaction is subjective and prone to false positive reporting. There are a multitude of tests on market that vary greatly in their sensitivity, specificity and limit of detection.

Qualitative FIT tests deliver a qualitative “Yes/No” result relating to a borderline score, which is set by the respective test manufacturer, is difficult to verify. This fixed cut off makes them impossible to adapt to local requirements and therefore not suitable for national screening program use.

Test principle OC-Sensor™

The test method is based on a latex agglutination reaction. Latex particles are used which are paired with specific polyclonal antibodies against human haemoglobin (anti-human-HbA0). These form specific bonds with the haemoglobin from the stool sample and there follows an agglutination of latex particles, which can be detected turbidimetrically (photometrically).

The change in absorbance per time unit resulting from the latex agglutination reaction is proportional to the concentration of haemoglobin in the sample. The concentration of haemoglobin in the patient’s sample can be reliably and precisely calculated on the basis of a calibration curve – produced with the aid of haemoglobin standards.

Analysis is fully automated and standardised through use of the dedicated OC-Sensor™ Instrumentation; the quantitative, measured results are objectively determined and documented by means of photometric (optical) analysis technology.

Internal control material enables the laboratory user to have immediate and independent monitoring and control of the test system used.

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