4 main benefits of a non-invasive bile acid malabsorption test
What is bile acid malabsorption?
Bile acid diarrhoea (BAD) – also known as bile acid malabsorption (BAM) – is a form of chronic diarrhoea, estimated to affect 1 % of people in the UK. The condition can be painful and debilitating, with sufferers experiencing numerous and daily episodes of watery and urgent bowel motions with faecal incontinence at times. Awareness of this particular type of diarrhoea is variable and there are limited options and availability for diagnostic testing.
Causes of bile acid diarrhoea
Bile acids are synthesised in the liver and travel to the stomach and small intestine during digestion to aid cholesterol excretion, fat absorption and stimulate intestinal motility. Once transit through the ileum has taken place, 95 % of bile acids are then reabsorbed into the bloodstream and return to the liver for reuse. If this enterohepatic recycling fails, excess amounts of bile acids enter the colon, causing diarrhoea where most of these acids are excreted.
Malabsorption occurs either when bile acid production exceeds absorption capacity – classified as primary BAD – or when the small intestine has been damaged by disease (e.g. Crohn’s or Coeliac), surgery (ileum resection, cholecystectomy or vagotomy) or radiotherapy – known as secondary BAD. Untreated, this can increase the risk of gallstones and kidney stones.
Treatment options
So, what can be done to treat BAD?
- A strict low-fat diet of less than 40 g of fat per day
- Prescription bile acid sequestrant medication (colestyramine, colestipol or colesevelam).
These drugs work by binding to the bile acid in the small intestine and preventing secretions into the colon. However, two of the medications need to be mixed with water and many patients find them unpalatable, while side effects can include bloating and abdominal pain, or constipation if the dose is too high. Unsurprisingly, there is a recognised problem of patients not complying to treatment regimes.
How do you diagnose bile acid diarrhoea?
Until now, the definitive diagnostic tool for BAD has been the SeHCAT test, which involves digestion of a capsule containing bile salts and a radioactive tracer, followed by two gamma scans one week apart. This measures the amount of compound that has been retained or lost from the body in faeces. However, the test is not available in all hospitals so, even if patients get the option to go to a referral centre, they’d have to make two long journeys over a couple of weeks. Because of this, it’s quite common for most patients with suspected BAD to just be prescribed with medication, regardless of whether their diagnosis has been confirmed or not. When you consider that only 70 % of patients have BAD-positive SeHCAT results, it can be assumed that 30 % of untested patients don’t actually need sequestrant medication.
A simple, non-invasive test for BAD
The faecal bile acid test is a non-invasive alternative to SeHCAT testing. This enzymatic assay is used to give a quantitative measure of bile acids present in faeces by analysis of concentrations of serum 7α-hydroxy-4-cholesten-3-one (C4). Patients with malabsorption show elevated values of serum C4, and results correlate well with low retention values on SeHCAT testing.
The potential benefits of FBA testing are simple:
- Improved access to testing – FBA is a simple test that all local diagnostic labs can conduct.
- Non-invasive testing – FBA testing is non-invasive and merely requires a single stool sample from the patient; testing can potentially be repeated if necessary.
- More efficient use of secondary care resources – an FBA positive result means treatment for BAD can start without the need for hospital testing or admission, reducing resource-heavy and costly tests and appointments.
- Improving patient experience and reducing unnecessary treatment – only patients with positive FBA results would receive treatment; a confirmed diagnosis will reduce prescriptions for unnecessary, expensive medications, and can also be used to persuade patients that taking the drug, however unpleasant, will lead to a successful outcome.
For more information or to try the FBA test, go to https://biohithealthcare.co.uk/biohit-product/faecal-bile-acids-assay-idk/
