Potential benefits of a promising technology to diagnose bile acid malabsorption to be explored further in new research
Draft guidance published today (31 July) as part of NICE's diagnostics assessment programme concludes that SeHCAT (GE Healthcare) is a potentially clinically important test for diagnosing bile acid malabsorptioni in people with diarrhoea predominant irritable bowel syndrome (IBS-D) and people with Crohn's disease without ileal resection, but that there is insufficient evidence at present to determine whether it is a useful and cost effective diagnostic test. The draft guidance therefore recommends that, for people with these conditions, SeHCAT is used in research settings in order that further evidence about its potential benefits can be generated.
Bile acids are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine. The liver secretes large amounts of bile acids into the intestine every day, but only relatively small quantities are lost from the body. This is because approximately 95% of the bile acids delivered to the duodenum are recycled back to the liver from the ileum (part of the small intestine).
Although bile acid malabsorption is a known cause of chronic diarrhoea (excess bile in the colon stimulates electrolyte and water secretion, which results in chronic watery diarrhoea), it is often misdiagnosed as diarrhoea-predominant irritable bowel disease (IBS-D). IBS is one of the most common reasons for referral to a gastrointestinal clinic and can account for as many as 1 in 20 referrals. However, its cause is often difficult to diagnose and patients may undergo several investigations, including those for inflammatory bowel disease, colonic cancer, coeliac disease and chronic infections, without a definitive cause being identified. Evidence suggests that as many as half a million patients in the NHS who are currently treated for IBS-D actually have bile acid malabsorption. Bile acid malabsorption is also associated with Crohn's disease, a chronic severe condition characterised by inflammation, ulcers and bleeding that may affect any part of the gastrointestinal tract, including the terminal ileum.
SeHCAT is a selenium-labelled synthetic bile salt that is licensed for use in measuring bile acid pool loss and investigating bile acid malabsorption. The technology is used, in conjunction with a full-body scan, to test the function of the bowel by measuring how well the compound is retained or lost from the body into the faeces.
Professor Carole Longson, NICE Health Technology Evaluation Centre Director, said: "Bile acid malabsorption is a condition for which treatments are available but which often goes undiagnosed. There may well be potential value associated with using SeHCAT but the relationship of bile acid malabsorption and its treatment to improving patient outcomes is complex and uncertain. The Committee concluded that there is currently not enough evidence to determine whether use of the technology is a useful approach for diagnosing bile acid malabsorption in people with chronic diarrhoea who have been diagnosed with IBS-D or Crohn's disease without ileal resection. But important research is needed to address this evidence gap. This is why we have passed the research needs to the NICE Medical Technologies Evaluation Programme research facilitation team for the development of specific research protocols as appropriate."
The draft diagnostics guidance for SeHCAT is available on the NICE website at http://guidance.nice.org.uk/DT/8 (from 31 July).
Notes to Editors
References and explanation of terms
i Bile acids are synthesised in the liver from cholesterol before being transferred in conjugated form to the bile ducts where they accumulate and are stored in the gall bladder. After a meal the gall bladder contracts and bile acids flow into the intestinal lumen. Most of the bile acids are then reabsorbed by the distal ileum into the portal circulation and returned to the liver. The bile acids are later secreted into the bile again as part of a recycling process called enterohepatic circulation. Although a small proportion of bile acids (3%) are excreted in the faeces, about 97% of bile acids are recycled.
In people with bile acid malabsorption, excess bile in the colon stimulates electrolyte and water secretion which results in chronic watery diarrhoea.
About the draft guidance
1. There is no direct comparator for this diagnostic test. Current diagnostic options include analysis of a patient's history, investigations to exclude ‘red flag' symptoms and a variety of other diagnostic tests such as blood tests and lactose tolerance tests. Trial of treatment is used, with mixed results, to diagnose bile acid malabsorption. However, it is not widely used in current practice.
2. The main comparator for the assessment is the tests and clinical observations contained in the British Society of Gastroenterology guidelines for the investigation of chronic diarrhoea.
3. SeHCAT comprises a capsule containing a synthetic analogue of the natural conjugated bile acid tauroselcholic acid and 75Selenium (a gamma-emitter). The radionuclide tracer atom allows SeHCAT to be easily detected in a whole body scan using a standard gamma camera. The technology is used to test the function of the bowel by measuring how well the compound is retained or lost from the body into the faeces. Retention values of less than 15% are considered abnormal and indicative of bile acid malabsorption. However, there is no definitive cut-off between normal and abnormal.
4. The acquisition cost of the SeHCAT capsule is £195. The cost of administering the SeHCAT test is £186
5. SeHCAT is manufactured by GE Healthcare
About the NICE Diagnostics Assessment Programme
6. Further information about the NICE diagnostics assessment programme can be found on the NICE website.
7. Topics to be considered by the Programme are routed through the related Medical Technologies Assessment Programme.
8. The National Institute for Health and Care Excellence (NICE) is the independent organisation responsible for providing national guidance and standards on the promotion of good health and the prevention and treatment of ill health.
9. NICE produces guidance in three areas of health:
- public health - guidance on the promotion of good health and the prevention of ill health for those working in the NHS, local authorities and the wider public and voluntary sector
- health technologies - guidance on the use of new and existing medicines, treatments, medical technologies (including devices and diagnostics) and procedures within the NHS
- clinical practice - guidance on the appropriate treatment and care of people with specific diseases and conditions within the NHS.
10. NICE produces standards for patient care:
- quality standards - these reflect the very best in high quality patient care, to help healthcare practitioners and commissioners of care deliver excellent services
- Quality and Outcomes Framework - NICE develops the clinical and health improvement indicators in the QOF, the Department of Health scheme which rewards GPs for how well they care for patients
11. NICE provides advice and support on putting NICE guidance and standards into practice through its implementation programme, and it collates and accredits high quality health guidance, research and information to help health professionals deliver the best patient care through NHS Evidence.
This page was last updated: 31 July 2012