Chief Investigator: Professor Ramesh Arasaradnam

Research Fellow: Dr Subashini Chandrapalan

Lead Coordinator: Shivam Joshi

University Hospitals Coventry and Warwickshire NHS Trust

Bowel Disease Research Foundation (now Bowel Research UK)

To evaluate the diagnostic performance of Faecal immunochemical test (FIT) and urine volatile organic compounds (VOC) in the detection of colorectal adenoma and to determine the positivity threshold for the above non-invasive testing.

Multi-centre, prospective diagnostic accuracy study

Gastroenterology

Bowel cancer can arise from polyps, which can become cancerous. Polyps are little outgrowths within the lining of the bowel (similar to skin warts). Depending on their size and their potential to become cancerous, they can cause bleeding. 

However, it is not known which polyps harbour cancerous potential. Therefore, at present all patients undergo a colonoscopy (camera examination of the large bowel) in order to identify and remove any polyps. However, not all patients who undergo a colonoscopy will have polyps. Moreover, colonoscopies are invasive and disruptive to patients, as they require bowel preparation. 

The aim of this study is to evaluate non-invasive stool and urine tests to identify patients who are at risk of polyps and if the polyps have the potential to become cancerous. This in turn, will significantly reduce the number of ‘unnecessary’ polyp surveillance colonoscopies with resultant benefits to both patients and the NHS.

30th September 2019

2 years

354

Colorectal polyp surveillance plays a major role in the prevention of colorectal cancer. Non-invasive screening modalities, therefore, attract considerable attention.

In this study, the performance of Faecal Immunochemical Testing (FIT) varied depending on the threshold levels chosen to identify patients with polyps. Overall, the sensitivity of FIT (i.e. the number of true positive cases) was higher at lower thresholds, whilst a steady decline in sensitivity was noted at higher cut-off levels. Higher specificity (i.e. the number of true negative cases) was observed at higher cut-off levels. FIT had shown a better performance in the detection of a high-risk finding. At the threshold of 10 ug/g faeces, the sensitivity and specificity of FIT for the detection of a high-risk finding were 0.54 (95% confidence interval (CI), 0.43 to 0.65) and 0.79 (95% CI, 0.73 to 0.84) respectively. Moreover, in our study, age, sex, proton pump inhibitor therapy, anticoagulation therapy, antiplatelet therapy and non-steroidal anti-inflammatory drugs did not have any effect on the performance of FIT.

The analysis of Volatile Organic Compounds (VOC) in the urine demonstrated that a high-risk finding could be differentiated with the area under curve of 0.74 (sensitivity of 0.92 (95% CI, 0.86 to 0.97) and specificity of 0.62 (95% CI, 0.55 to 0.68).

The combined performance of FIT and VOC, in a serial testing manner, was superior to either of those tests conducted alone.

The combination of FIT and VOC can be utilised in polyp surveillance, as a triage tool in risk-stratifying patients.