SeHCAT [tauroselcholic (selenium-75) acid] for the investigation of bile acid malabsorption and measurement of bile acid pool loss: a systematic review and cost-effectiveness analysis.

BACKGROUND: The principal diagnosis/indication for this assessment is chronic diarrhoea due to bile acid malabsorption (BAM). Diarrhoea can be defined as the abnormal passage of loose or liquid stools more than three times daily and/or a daily stool weight > 200 g per day and is considered to be chronic if it persists for more than 4 weeks. The cause of chronic diarrhoea in adults is often difficult to ascertain and patients may undergo several investigations without a definitive cause being identified. BAM is one of several causes of chronic diarrhoea and results from failure to absorb bile acids (which are required for the absorption of dietary fats and sterols in the intestine) in the distal ileum. OBJECTIVE: For people with chronic diarrhoea with unknown cause and in people with Crohn's disease and chronic diarrhoea with unknown cause (i.e. before resection): (1) What are the effects of selenium-75-homocholic acid taurine (SeHCAT) compared with no SeHCAT in terms of chronic diarrhoea, other health outcomes and costs? (2) What are the effects of bile acid sequestrants (BASs) compared with no BASs in people with a positive or negative SeHCAT test? (3) Does a positive or negative SeHCAT test predict improvement in terms of chronic diarrhoea, other health outcomes and costs? DATA SOURCES: A systematic review was conducted to summarise the evidence on the clinical effectiveness of SeHCAT for the assessment of BAM and the measurement of bile acid pool loss. Search strategies were based on target condition and intervention, as recommended in the Centre for Reviews and Dissemination (CRD) guidance for undertaking reviews in health care and the Cochrane Handbook for Diagnostic Test Accuracy Reviews. The following databases were searched up to April 2012: MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; EMBASE; the Cochrane Databases; Database of Abstracts of Reviews of Effects; Health Technology Assessment (HTA) Database; and Science Citation Index. Research registers and conference proceedings were also searched. REVIEW METHODS: Systematic review methods followed the principles outlined in the CRD guidance for undertaking reviews in health care and the National Institute for Health and Care Excellence (NICE) Diagnostic Assessment Programme interim methods statement. In the health economic analysis, the cost-effectiveness of SeHCAT for the assessment of BAM, in patients with chronic diarrhoea, was estimated in two different populations. The first is the population of patients with chronic diarrhoea with unknown cause and symptoms suggestive of diarrhoea-predominant irritable bowel syndrome (IBS-D) and the second population concerns patients with Crohn's disease without ileal resection with chronic diarrhoea. For each population, three models were combined: (1) a short-term decision tree that models the diagnostic pathway and initial response to treatment (first 6 months); (2) a long-term Markov model that estimates the lifetime costs and effects for patients initially receiving BAS; and (3) a long-term Markov model that estimates the lifetime costs and effects for patients initially receiving regular treatment (IBS-D treatment in the first population and Crohn's treatment in the second population). Incremental cost-effectiveness ratios were estimated as additional cost per additional responder in the short term (first 6 months) and per additional quality-adjusted life-year (QALY) in the long term (lifetime). RESULTS: We found three studies assessing the relationship between the SeHCAT test and response to treatment with cholestyramine. However, the studies had small numbers of patients with unknown cause chronic diarrhoea, and they used different cut-offs to define BAM. For the short term (first 6 months), when trial of treatment is not considered as a comparator, the optimal choice depends on the willingness to pay for an additional responder. For lower values (between £1500 and £4600) the choice will be no SeHCAT in all scenarios; for higher values either SeHCAT 10% or SeHCAT 15% becomes cost-effective. For the lifetime perspective, the various scenarios showed widely differing results: in the threshold range of £20,000-30,000 per QALY gained we found as optimal choice either no SeHCAT, SeHCAT 5% (only IBS-D) or SeHCAT 15%. When trial of treatment is considered a comparator, the analysis showed that for the short term, trial of treatment is the optimal choice across a range of scenarios. For the lifetime perspective with trial of treatment, again the various scenarios show widely differing results. Depending on the scenario, in the threshold range of £20,000-30,000 per QALY gained, we found as optimal choice either trial of treatment, no SeHCAT or SeHCAT 15%. CONCLUSIONS: In conclusion, the various analyses show that for both populations considerable decision uncertainty exists and that no firm conclusions can be formulated about which strategy is optimal. Standardisation of the definition of a positive SeHCAT test should be the first step in assessing the usefulness of this test. As there is no reference standard for the diagnosis of BAM and SeHCAT testing provides a continuous measure of metabolic function, diagnostic test accuracy (DTA) studies are not the most appropriate study design. However, in studies where all patients are tested with SeHCAT and all patients are treated with BASs, response to treatment can provide a surrogate reference standard; further DTA studies of this type may provide information on the ability of SeHCAT to predict response to BASs. A potentially more informative option would be multivariate regression modelling of treatment response (dependent variable), with SeHCAT result and other candidate clinical predictors as covariates. Such a study design could also inform the definition of a positive SeHCAT result. STUDY REGISTRATION: The study is registered as PROSPERO CRD42012001911. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

Rapid fetal fibronectin testing to predict preterm birth in women with symptoms of premature labour: a systematic review and cost analysis.

BACKGROUND: Premature birth is defined as birth of before 37 completed weeks' gestation. Not all pregnant women showing symptoms of preterm labour will go on to deliver before 37 weeks' gestation. Hence, addition of fetal fibronectin (fFN) testing to the diagnostic workup of women with suspected preterm labour may help to identify those women who do not require active management, and thus avoid unnecessary interventions, hospitalisations and associated costs. OBJECTIVE: To assess the clinical effectiveness and cost-effectiveness of rapid fFN testing in predicting preterm birth (PTB) in symptomatic women. DATA SOURCES: Bibliographic databases (including EMBASE, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials) were searched from 2000 to September/November 2011. Trial registers were also searched. REVIEW METHODS: Systematic review methods followed published guidance; we assessed clinical effectiveness and updated a previous systematic review of test accuracy. Risk of bias was assessed using the Cochrane tool (randomised controlled trials; RCTs) and a modification of QUADAS-2 (diagnostic test accuracy studies; DTAs). Summary risk ratios or weighted mean difference were calculated using random-effects models. Summary sensitivity and specificity used a bivariate summary receiver operating characteristic model. Heterogeneity was investigated using subgroup and sensitivity analyses. Health economic analysis focused on cost consequences. The time horizon was hospital admission for observation. A main structural assumption was that, compared with usual care, fFN testing doesn't increase adverse events or negative pregnancy outcomes. RESULTS: Five RCTs and 15 new DTAs were identified. No RCT reported significant effects of fFN testing on maternal or neonatal outcomes. One study reported a subgroup analysis of women with negative fFN test observed > 6 hours, which showed a reduction in length of hospital stay where results were known to clinicians. Combining data from new studies and the previous systematic review, the pooled estimates of sensitivity and specificity were: 76.7% and 82.7% for delivery within 7-10 days of testing; 69.1% and 84.4% for delivery < 34 weeks' gestation; and 60.8% and 82.3% for delivery < 37 weeks' gestation. Estimates were similar across all subgroups sensitivity analyses. The base-case cost analysis resulted in a cost saving of £23.87 for fFN testing compared with usual care. The fFN testing was cost-neutral at an approximate cost of £45. Probabilistic sensitivity analysis gave an incremental cost (saving) of -£25.59 (97.5% confidence interval -£304.96 to £240.06), indicating substantial uncertainty. Sensitivity analyses indicated that admission rate had the largest impact on results. CONCLUSIONS: Fetal fibronectin testing has moderate accuracy for predicting PTB. The main potential role is likely to be reducing health-care resource usage by identifying women not requiring intervention. Evidence from RCTs suggests that fFN does not increase adverse outcomes and may reduce resource use. The base-case analysis showed a modest cost difference in favour of fFN testing, which is largely dependent on whether or not fFN testing reduces hospital admission. Currently, there are no high-quality studies and the existing trials were generally underpowered. Hence, there is a need for high-quality adequately powered trials using appropriate study designs to confirm the findings presented. STUDY REGISTRATION: PROSPERO 2011:CRD42011001468. Available from www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42011001468. FUNDING: The National Institute for Health Research Health Technology Assessment programme.