6 Considerations

6 Considerations

6.1 The Committee considered the prevalence of bile acid malabsorption in people with chronic diarrhoea diagnosed with either IBS-D or Crohn's disease without ileal resection. Although studies have shown that as many as 30% of people with IBS-D have bile acid malabsorption, it is not clear whether the bile acid malabsorption is a primary idiopathic condition or secondary to another condition, which can determine the effectiveness of subsequent treatment. The Committee was informed that there are several causes of bile acid malabsorption, including that it may be a consequence of the decreased transit time associated with diarrhoea.

6.2 The Committee considered the diagnostic accuracy of SeHCAT. The Committee was informed that there are no clinical validity results for SeHCAT, and that the diagnostic accuracy of SeHCAT has only been determined by response to treatment with bile acid sequestrants, which may be open to assessment bias because of an inability to blind patients and clinicians.

6.3 The Committee considered how good the repeatability is for SeHCAT testing. The Committee was informed that, in people with IBS-D, the result of a SeHCAT test may vary depending on when in the course of the condition it is administered, because the disease is quite variable over time. The Committee was informed that there is likely to be less variability with other conditions but, because of the nature of the test (namely dependency on the use of radio-isotopes with relatively long half-lives), formal repeatability assessments would be difficult.

6.4 The Committee discussed the effectiveness of bile acid sequestrants in treating bile acid malabsorption. The Committee was informed that there is little evidence on the clinical effectiveness of bile acid sequestrants. Moreover, it is not clear whether, in people with bile acid malabsorption, bile acid sequestrants work by binding bile acids, by a more direct constipating effect, or by a placebo effect. The Committee was also informed that a soon-to-be published study suggests that bile acid sequestrants may reduce bile acid malabsorption by reducing transit time rather than through binding bile acids, which may imply other more tolerable treatments could be effective.

6.5 The Committee considered the validity of a trial of treatment with bile acid sequestrants as a comparator to SeHCAT. The Committee was informed that a trial of treatment may work if the clinician persuades the person to adhere to the treatment. But a trial may not be suitable for the population groups included in this assessment because the efficacy of treatment is dose sensitive and because the treatment is not well tolerated. This means that achieving adherence during the treatment trial can be challenging. The Committee was informed that the results of a SeHCAT test help to guide the clinician in the titration of the dose of bile acid sequestrants and to provide an incentive for adherence to treatment. The Committee was also informed that a positive diagnosis is likely to increase adherence among people prescribed bile acid sequestrants. The Committee was also informed that no studies were identified that quantified the accuracy and effectiveness of a trial of treatment.

6.6 The Committee considered what other options are available for diagnosing bile acid malabsorption. The Committee was informed that there are currently laboratory-based tests being developed, whereas older methods such as faecal bile acid measurements are not routinely practised.

6.7 The Committee was informed by the manufacturer that 30–40% of gastrointestinal centres in the country use SeHCAT and that the number is rising. The Committee was informed by clinical specialists that SeHCAT is mostly used in teaching hospitals and universities. The specialists also agreed that the use of SeHCAT has increased substantially in the past 2 years.

6.8 The Committee considered the cost-effectiveness analysis in the diagnostic assessment report. The report contained multiple scenario analyses because of the paucity of the evidence. SeHCAT use in the populations under evaluation was variably cost effective depending on the assumptions used in the scenario. The Committee was informed that it is extremely difficult to establish transition probabilities from 'diarrhoea' to 'no diarrhoea'. As such, the Committee was unable to establish the relative plausibility of these scenarios.

6.9 The Committee concluded that, given the apparent prevalence of undiagnosed bile acid malabsorption, there is the potential for patient and system benefit associated with using SeHCAT. But the Committee concluded that there is currently insufficient evidence to determine whether and under what circumstances SeHCAT is a cost-effective option for diagnosing bile acid malabsorption in people with chronic diarrhoea who have been diagnosed with IBS-D or Crohn's disease without ileal resection. The Committee agreed that a programme of research was needed to evaluate this technology, the condition and the effects of treatment, and that its research recommendations would stimulate the collection of evidence about the potentially important clinical benefits and potential harms of using SeHCAT and treating bile acid malabsorption.

6.10 The Committee was aware that people with chronic diarrhoea are likely to be classified as having a disability and therefore be protected under the Equality Act 2010. The Committee considered the potential impact a negative recommendation or a recommendation for further research could have on this population. It was felt that given the cost of the test and the unpleasantness of the treatment, research was essential to establish cost effectiveness and benefit for this population, and that the population would be best served by research, including research to address the acceptability of treatment, before the recommendation of widespread adoption of this test.

  • National Institute for Health and Care Excellence (NICE)