Diagnostic strategies using DNA testing for hereditary haemochromatosis in at-risk populations: a systematic review and economic evaluation

Use of Decision Modelling in Economic Evaluations of Diagnostic Tests: An Appraisal and Review of Health Technology Assessments in the UK

Diagnostic tests play an important role in the clinical decision-making process by providing information that enables patients to be identified and stratified to the most appropriate treatment and management strategies. Decision analytic modelling facilitates the synthesis of evidence from multiple sources to evaluate the cost effectiveness of diagnostic tests. This study critically reviews the methods used to model the cost effectiveness of diagnostic tests in UK National Institute for Health Research (NIHR) Health Technology Assessment (HTA) reports. UK NIHR HTA reports published between 2009 and 2018 were screened to identify those reporting an economic evaluation of a diagnostic test using decision analytic modelling. Existing decision modelling checklists were identified in the literature and a modified checklist tailored to diagnostic economic evaluations was developed, piloted and used to assess the diagnostic models in HTA reports. Of 728 HTA reports published during the study period, 55 met the inclusion criteria. The majority of models performed well with a clearly defined decision problem and analytical perspective (89% of HTAs met the criterion). The model structure usually reflected the care pathway and progression of the health condition. However, there are areas requiring improvement. These are predominantly systematic identification of treatment effects (20% met), poor selection of comparators (50% met) and assumed independence of tests used in sequence (32% took correlation between sequential tests into consideration). The complexity and constraints of performing decision analysis of diagnostic tests on costs and health outcomes makes it particularly challenging and, as a result, quality issues remain. This review provides a comprehensive assessment of modelling in HTA reports, highlights problems and gives recommendations for future diagnostic modelling practice.

Evidence synthesis to inform model-based cost-effectiveness evaluations of diagnostic tests: a methodological review of health technology assessments

BACKGROUND

Evaluations of diagnostic tests are challenging because of the indirect nature of their impact on patient outcomes. Model-based health economic evaluations of tests allow different types of evidence from various sources to be incorporated and enable cost-effectiveness estimates to be made beyond the duration of available study data. To parameterize a health-economic model fully, all the ways a test impacts on patient health must be quantified, including but not limited to diagnostic test accuracy.

METHODS

We assessed all UK NIHR HTA reports published May 2009-July 2015. Reports were included if they evaluated a diagnostic test, included a model-based health economic evaluation and included a systematic review and meta-analysis of test accuracy. From each eligible report we extracted information on the following topics: 1) what evidence aside from test accuracy was searched for and synthesised, 2) which methods were used to synthesise test accuracy evidence and how did the results inform the economic model, 3) how/whether threshold effects were explored, 4) how the potential dependency between multiple tests in a pathway was accounted for, and 5) for evaluations of tests targeted at the primary care setting, how evidence from differing healthcare settings was incorporated.

RESULTS

The bivariate or HSROC model was implemented in 20/22 reports that met all inclusion criteria. Test accuracy data for health economic modelling was obtained from meta-analyses completely in four reports, partially in fourteen reports and not at all in four reports. Only 2/7 reports that used a quantitative test gave clear threshold recommendations. All 22 reports explored the effect of uncertainty in accuracy parameters but most of those that used multiple tests did not allow for dependence between test results. 7/22 tests were potentially suitable for primary care but the majority found limited evidence on test accuracy in primary care settings.

CONCLUSIONS

The uptake of appropriate meta-analysis methods for synthesising evidence on diagnostic test accuracy in UK NIHR HTAs has improved in recent years. Future research should focus on other evidence requirements for cost-effectiveness assessment, threshold effects for quantitative tests and the impact of multiple diagnostic tests.

Psychological Aspects of Bariatric Surgery as a Treatment for Obesity

PURPOSE OF REVIEW

Little is known about the psychological effects on life after bariatric surgery despite the high prevalence of psychological disorders in candidates seeking this procedure. Our review discusses the literature around the psychological impact of bariatric surgery, exploring whether the procedure addresses underlying psychological conditions that can lead to morbid obesity and the effect on eating behaviour postoperatively.

RECENT FINDINGS

Findings show that despite undisputed significant weight loss and improvements in comorbidities, current literature suggests some persisting disorder in psychological outcomes like depression and body image for patients at longer term follow-up, compared to control groups. Lack of postoperative psychological monitoring and theoretical mapping limits our understanding of reasons behind these findings. Reframing bariatric approaches to morbid obesity to incorporate psychological experience postoperatively would facilitate understanding of psychological aspects of bariatric surgery and how this surgical treatment maps onto the disease trajectory of obesity.

A Systematic Review and Narrative Synthesis of Health Economic Studies Conducted for Hereditary Haemochromatosis

BACKGROUND

Hereditary haemochromatosis (HH) is a common genetic condition amongst people of northern European heritage. HH is associated with increased iron absorption leading to parenchymal organ damage and multiple arthropathies. Early diagnosis and treatment prevents complications. Population screening may increase early diagnosis, but no programmes have been introduced internationally: a paucity of health economic data is often cited as a barrier.

OBJECTIVE

To conduct a systematic review of all health economic studies in HH.

METHODS

Studies were identified through electronic searching of economic/biomedical databases. Any study on HH with original economic component was included. Study quality was formally assessed. Health economic data were extracted and analysed through narrative synthesis.

RESULTS

Thirty-eight studies met the inclusion criteria. The majority of papers reported on costs or cost effectiveness of screening programmes. Whilst most concluded screening was cost effective compared with no screening, methodological flaws limit the quality of these findings. Assumptions regarding clinical penetrance, effectiveness of screening, health-state utility values (HSUVs), exclusion of early symptomatology (such as fatigue, lethargy and multiple arthropathies) and quantification of costs associated with HH were identified as key limitations. Treatment studies concluded therapeutic venepuncture was the most cost-effective intervention.

CONCLUSIONS

There is a paucity of high-quality health economic studies relating to HH. The development of a comprehensive HH cost-effectiveness model utilising HSUVs is required to determine whether screening is worthwhile.

Cascade testing of primary care blood samples with hyperferritinaemia identifies subjects with iron overload and porphyria cutanea tarda

Introduction

Serum ferritin is routinely used as a first line test for iron status. Testing subjects with low pre-test probability often results in unexpected abnormal results. Raised ferritin is typically found in subjects with iron overload, liver disease, malignancy or inflammation. We sought to determine whether primary care patients with high ferritin had either porphyria cutanea tarda (PCT) or hereditary haemochromatosis (HH).

Methods

Redundant serum samples were collected from consecutive specimens with high ferritin (>500 µg/L) which had been received from primary care sources. Samples were analysed for serum iron and iron-binding capacity and for porphyrins by fluorescence scanning and HPLC.

Results

There were 240 samples (91 females, 149 males) which represented 2.7% of total over the collection period. Serum iron was 17.3 (18.9) µmol/L (median (IQR)), TIBC 47.3 (14.2) µmol/L and transferrin saturation 35.7 (41.1) %. There were 87/240 (36%) with transferrin saturation >45% (57 males, 30 females). Of the samples 19/236 (8%) were positive for porphyrins by spectrofluorimetry and 14/15 (4 insufficient sample) had total porphyrins >11.2 nmol/L (40(63) median (IQR)) with 3/15 (1.25%) having a typical pattern for PCT.

Discussion

This study demonstrates the feasibility of cascading tests using laboratory protocols and confirms the ability to identify potential cases. However, further studies for HH genotype and urine and stool porphyrin analysis will be necessary to confirm the diagnoses.

Ethical issues raised by common copy number variants and single nucleotide polymorphisms of certain and uncertain significance in general medical practice

The ethical issues surrounding genotyping for single nucleotide polymorphisms (SNPs) or for copy number variation (CNV) are very different. SNP genotyping can focus on ancestry, risk probability, single gene diagnosis, pharmacogenetics, and carrier testing, and the combination of these in a single test can present difficulties. The interpretation of such tests, inconsistencies between laboratories, and access to genotype information for future reference need to be considered, as well as the value of genotypes of known clinical significance compared with those that provide modest risk modifications with limited potential to take medically useful steps. For CNV genotyping, the major concerns relate to CNVs of uncertain significance and to those with incomplete penetrance. Such CNVs present acute difficulties in counseling symptomatic and asymptomatic individuals and have substantial potential for stigmatization of both groups, as well as raising difficulties when detected in prenatal diagnosis. Improved prenatal diagnosis of many disorders provided by array tests compared with the traditional karyotype probably outweighs the uncertainties for families who would terminate pregnancies with findings associated with severe disabilities. There are substantive concerns about offering SNP or CNV genotyping direct to consumers without a physician or counselor to provide guidance for interpretation of the results.