Sex differences in national rates of repair of emergency abdominal aortic aneurysm

BACKGROUND

The aim of this study was to assess the sex differences in both the rate and type of repair for emergency abdominal aortic aneurysm (AAA) in England.

METHODS

Hospital Episode Statistics (HES) data sets from April 2002 to February 2015 were obtained. Clinical and administrative codes were used to identify patients who underwent primary emergency definitive repair of ruptured or intact AAA, and patients with a diagnosis of AAA who died in hospital without repair. These three groups included all patients with a primary AAA who presented as an emergency. Sex differences between repair rates and type of surgery (endovascular aneurysm repair (EVAR) versus open repair) over time were examined.

RESULTS

In total, 15 717 patients (83·3 per cent men) received emergency surgical intervention for ruptured AAA and 10 276 (81·2 per cent men) for intact AAA; 12 767 (62·0 per cent men) died in hospital without attempted repair. The unadjusted odds ratio for no repair in women versus men was 2·88 (95 per cent c.i. 2·75 to 3·02). Women undergoing repair of ruptured AAA were older and had a higher in-hospital mortality rate (50·0 versus 41·0 per cent for open repair; 30·9 versus 23·5 per cent for EVAR). After adjustment for age, deprivation and co-morbidities, the odds ratio for no repair in women versus men was 1·34 (1·28 to 1·40). The in-hospital mortality rate after emergency repair of an intact AAA was also higher among women.

CONCLUSION

Women who present as an emergency with an AAA are less likely to undergo repair than men. Although some of this can be explained by differences in age and co-morbidities, the differences persist after case-mix adjustment.

Looking beyond the forest: Using harvest plots, gap analysis, and expert consultations to assess effectiveness, engage stakeholders, and inform policy

We describe a combination of methods for assessing the effectiveness of complex interventions, especially where substantial heterogeneity with regard to the population, intervention, comparison, outcomes, and study design of interest is expected. We applied these methods in a recent systematic review of the effectiveness of reinforced home-based palliative care (rHBPC) interventions, which included home-based care with an additional and explicit component of lay caregiver support. We first summarized the identified evidence, deemed inappropriate for statistical pooling, graphically by creating harvest plots. Although very useful as a tool for summary and presentation of overall effectiveness, such graphical summary approaches may obscure relevant differences between studies. Thus, we then used a gap analysis and conducted expert consultations to look beyond the aggregate level at how the identified evidence of effectiveness may be explained. The goal of these supplemental methods was to step outside of the conventional systematic review and explore this heterogeneity from a broader perspective, based on the experience of palliative care researchers and practitioners. The gap analysis and expert consultations provided valuable input into possible underlying explanations in the evidence, which could be helpful in the further adaptation and testing of existing rHBPC interventions or the development and evaluation of new ones. We feel that such a combination of methods could prove accessible, understandable, and useful in informing decisions and could thus help increase the relevance of systematic reviews to the decision-making process.

Cost-effectiveness of population-based, community, workplace and individual policies for diabetes prevention in the UK

AIM

To analyse the cost-effectiveness of different interventions for Type 2 diabetes prevention within a common framework.

METHODS

A micro-simulation model was developed to evaluate the cost-effectiveness of a range of diabetes prevention interventions including: (1) soft drinks taxation; (2) retail policy in socially deprived areas; (3) workplace intervention; (4) community-based intervention; and (5) screening and intensive lifestyle intervention in individuals with high diabetes risk. Within the model, individuals follow metabolic trajectories (for BMI, cholesterol, systolic blood pressure and glycaemia); individuals may develop diabetes, and some may exhibit complications of diabetes and related disorders, including cardiovascular disease, and eventually die. Lifetime healthcare costs, employment costs and quality-adjusted life-years are collected for each person.

RESULTS

All interventions generate more life-years and lifetime quality-adjusted life-years and reduce healthcare spending compared with doing nothing. Screening and intensive lifestyle intervention generates greatest lifetime net benefit (£37) but is costly to implement. In comparison, soft drinks taxation or retail policy generate lower net benefit (£11 and £11) but are cost-saving in a shorter time period, preferentially benefit individuals from deprived backgrounds and reduce employer costs.

CONCLUSION

The model enables a wide range of diabetes prevention interventions to be evaluated according to cost-effectiveness, employment and equity impacts over the short and long term, allowing decision-makers to prioritize policies that maximize the expected benefits, as well as fulfilling other policy targets, such as addressing social inequalities.

The impact of Type 2 diabetes prevention programmes based on risk-identification and lifestyle intervention intensity strategies: a cost-effectiveness analysis

AIMS

To develop a cost-effectiveness model to compare Type 2 diabetes prevention programmes targeting different at-risk population subgroups with a lifestyle intervention of varying intensity.

METHODS

An individual patient simulation model was constructed to simulate the development of diabetes in a representative sample of adults without diabetes from the UK population. The model incorporates trajectories for HbA1c , 2-h glucose, fasting plasma glucose, BMI, systolic blood pressure, total cholesterol and HDL cholesterol. Patients can be diagnosed with diabetes, cardiovascular disease, microvascular complications of diabetes, cancer, osteoarthritis and depression, or can die. The model collects costs and utilities over a lifetime horizon. The perspective is the UK National Health Service and personal social services. We used the model to evaluate the population-wide impact of targeting a lifestyle intervention of varying intensity to six population subgroups defined as high risk for diabetes.

RESULTS

The intervention produces 0.0003 to 0.0009 incremental quality-adjusted life years and saves up to £1.04 per person in the general population, depending upon the subgroup targeted. Cost-effectiveness increases with intervention intensity. The most cost-effective options are to target individuals with HbA1c > 42 mmol/mol (6%) or with a high Finnish Diabetes Risk (FINDRISC) probability score (> 0.1).

CONCLUSION

The model indicates that diabetes prevention interventions are likely to be cost-effective and may be cost-saving over a lifetime. In the model, the criteria for selecting at-risk individuals differentially impact upon diabetes and cardiovascular disease outcomes, and on the timing of benefits. These findings have implications for deciding who should be targeted for diabetes prevention interventions.

A statistical model to describe longitudinal and correlated metabolic risk factors: the Whitehall II prospective study

Background

Novel epidemiology models are required to link correlated variables over time, especially haemoglobin A1c (HbA1c) and body mass index (BMI) for diabetes prevention policy analysis. This article develops an epidemiology model to correlate metabolic risk factor trajectories.

Method

BMI, fasting plasma glucose, 2-h glucose, HbA1c, systolic blood pressure, total cholesterol and high density lipoprotein (HDL) cholesterol were analysed over 16 years from 8150 participants of the Whitehall II prospective cohort study. Latent growth curve modelling was employed to simultaneously estimate trajectories for multiple metabolic risk factors allowing for variation between individuals. A simulation model compared simulated outcomes with the observed data.

Results

The model identified that the change in BMI was associated with changes in glycaemia, total cholesterol and systolic blood pressure. The statistical analysis quantified associations among the longitudinal risk factor trajectories. Growth in latent glycaemia was positively correlated with systolic blood pressure and negatively correlated with HDL cholesterol. The goodness-of-fit analysis indicates reasonable fit to the data.

Conclusions

This is the first statistical model that estimates trajectories of metabolic risk factors simultaneously for diabetes to predict joint correlated risk factor trajectories. This can inform comparisons of the effectiveness and cost-effectiveness of preventive interventions, which aim to modify metabolic risk factors.

Guaiac faecal occult blood test performance at initial and repeat screens in the English Bowel Cancer Screening Programme

BACKGROUND

In many countries, screening for colorectal cancer (CRC) relies on repeat testing using the guaiac faecal occult blood test (gFOBT). This study aimed to compare gFOBT performance measures between initial and repeat screens.

METHODS

Data on screening uptake and outcomes from the English Bowel Cancer Screening Programme (BCSP) for the years 2008 and 2011 were used. An existing CRC natural history model was used to estimate gFOBT sensitivity and specificity, and the cost-effectiveness of different screening strategies.

RESULTS

The gFOBT sensitivity for CRC was estimated to decrease from 27.35% at the initial screen to 20.22% at the repeat screen. Decreases were also observed for the positive predictive value (8.4-7.2%) and detection rate for CRC (0.19-0.14%). Assuming equal performance measures for both the initial and repeat screens led to an overestimate of the cost effectiveness of gFOBT screening compared with the other screening modalities.

CONCLUSIONS

Performance measures for gFOBT screening were generally lower in the repeat screen compared with the initial screen. Screening for CRC using gFOBT is likely to be cost-effective; however, the use of different screening modalities may result in additional benefits. Future economic evaluations of gFOBT should not assume equal sensitivities between screening rounds.

Modelling the economics of type 2 diabetes mellitus prevention: a literature review of methods

Our objective was to review modelling methods for type 2 diabetes mellitus prevention cost-effectiveness studies. The review was conducted to inform the design of a policy analysis model capable of assisting resource allocation decisions across a spectrum of prevention strategies. We identified recent systematic reviews of economic evaluations in diabetes prevention and management of obesity. We extracted studies from two existing systematic reviews of economic evaluations for the prevention of diabetes. We extracted studies evaluating interventions in a non-diabetic population with type 2 diabetes as a modelled outcome, from two systematic reviews of obesity intervention economic evaluations. Databases were searched for studies published between 2008 and 2013. For each study, we reviewed details of the model type, structure, and methods for predicting diabetes and cardiovascular disease. Our review identified 46 articles and found variation in modelling approaches for cost-effectiveness evaluations for the prevention of type 2 diabetes. Investigation of the variables used to estimate the risk of type 2 diabetes suggested that impaired glucose regulation, and body mass index were used as the primary risk factors for type 2 diabetes. A minority of cost-effectiveness models for diabetes prevention accounted for the multivariate impacts of interventions on risk factors for type 2 diabetes. Twenty-eight cost-effectiveness models included cardiovascular events in addition to type 2 diabetes. Few cost-effectiveness models have flexibility to evaluate different intervention types. We conclude that to compare a range of prevention interventions it is necessary to incorporate multiple risk factors for diabetes, diabetes-related complications and obesity-related co-morbidity outcomes.

Community-based dietary and physical activity interventions in low socioeconomic groups in the UK: a mixed methods systematic review

OBJECTIVE

Low socioeconomic status (SES) is a risk factor for type 2 diabetes and changes in diet and physical activity can prevent diabetes. We assessed the effectiveness and acceptability of community-based dietary and physical activity interventions among low-SES groups in the UK.

METHOD

We searched relevant databases and web resources from 1990 to November 2009 to identify relevant published and grey literature using an iterative approach, focusing on UK studies.

RESULTS

Thirty-five relevant papers (nine quantitative, 23 qualitative and three mixed methods studies) were data extracted, quality assessed and synthesised using narrative synthesis and thematic analysis. The relationship between interventions and barriers and facilitators was also examined. Dietary/nutritional, food retail, physical activity and multi-component interventions demonstrated mixed effectiveness. Qualitative studies indicated a range of barriers and facilitators, which spanned pragmatic, social and psychological issues. The more effective interventions used a range of techniques to address some surface-level psychological and pragmatic concerns, however many deeper-level social, psychological and pragmatic concerns were not addressed.

CONCLUSION

Evidence on the effectiveness of community-based dietary and physical activity interventions is inconclusive. A range of barriers and facilitators exist, some of which were addressed by interventions but some of which require consideration in future research.

Laparoscopic adjustable gastric banding vs standard medical management in obese patients with type 2 diabetes: a budget impact analysis in the UK

OBJECTIVE

To evaluate the financial consequences of using laparoscopic adjustable gastric banding (LAGB) in place of standard medical management (SMM) in obese patients with type 2 diabetes from a UK healthcare payer perspective.

DESIGN AND METHODS

A budget impact model was constructed to evaluate the budgetary implications of LAGB in obese patients with type 2 diabetes in the UK. For patients undergoing LAGB, the model captured pre-, peri-, and post-operative costs including consultations with physicians, psychologists, nurses, and dieticians, the cost of surgery, and costs associated with post-surgical complications. The model also captured costs associated with medication for diabetes, asthma, hypertension, and hyperlipidemia, costs of diabetes complications, sleep apnea, and asthma, and costs of diagnostic tests. The SMM arm also captured costs associated with very low calorie diet products. Costs were modeled in a simulated UK cohort of 100 obese patients with newly-diagnosed diabetes. Future costs were discounted at 3.5% per annum and all costs were reported in 2010 pounds sterling.

RESULTS

Over the 5-year time horizon, the cohort of 100 patients who underwent LAGB incurred costs £91,287 lower than an equivalent cohort receiving SMM (£818,668 and £909,955, respectively). Costs of surgery and post-surgical complications (£254,000 and £40,981, respectively) were more than offset by savings arising from reduced diabetes, asthma, and sleep apnea medication costs, reduced incidence of diabetes complications, and fewer healthcare professional contacts. Sensitivity analysis (SA) showed that the model was most sensitive to assumptions around diabetes medication use, although none of the SA findings showed LAGB to be more costly than SMM.

LIMITATIONS

In order to capture the diverse resource use and medical care costs arising in obese patients with type 2 diabetes, the analysis made use of a range of heterogeneous data sources. While the vast majority of data were applicable to obese patients with recently-diagnosed diabetes in the UK setting, some surrogate data (e.g. from different geographies) were used in cases where data in the target population were unavailable. Additionally, given the largely uncharacterized long-term risk profile in patients with remission of type 2 diabetes, remission was captured using a transparent and highly conservative approach.

CONCLUSIONS

Based on the findings of the present analysis, the high initial costs of performing LAGB are offset within 5 years after surgery when compared with SMM in a population of obese patients with type 2 diabetes. The high up-front costs associated with surgery should not therefore be a barrier to its reimbursement in this patient group.

Reappraisal of the options for colorectal cancer screening in England

AIM

The aim was to use newly available data to estimate the cost effectiveness and endoscopy requirements of screening options for colorectal cancer (CRC) to inform screening policy in England.

METHODS

A state transition model simulated the life experience of a cohort of individuals in the general population of England with normal colon/rectal epithelium through to the development of adenomas and CRC and subsequent death. CRC natural history model parameters and screening test characteristics were estimated simultaneously by a process of model calibration. This process was fitted to observed data on CRC incidence in the absence of screening, data from existing screening programmes, and data from the UK flexible sigmoidoscopy (FS) screening trial. The costs, effects and resource impact were evaluated for a range of screening options involving the guaiac or immunochemical faecal occult blood test (gFOBT/iFOBT) and FS.

RESULTS

The model suggests that screening strategies involving FS or iFOBT may produce additional benefits compared with the current policy of biennial gFOBT for 60-74-year-olds. The age at which a single FS screen results in the greatest quality-adjusted life year gain was 55, with similar gains for ages between 52 and 58. Strategies which combined FS and iFOBT showed further benefits and improved economic outcomes.

CONCLUSIONS

Strategies which combine different screening modalities may provide greater clinical and economic benefits. The collection of comprehensive screening data using a uniform format will enable comparative analysis across screening programmes in different countries, will improve our understanding of the disease and will allow identification of optimal screening modalities.

Cost of care for colorectal cancer in Ireland: a health care payer perspective

OBJECTIVE

Management options for colorectal cancer have expanded in recent years. We estimated average lifetime cost of care for colorectal cancer in Ireland in 2008, from the health care payer perspective.

METHOD

A decision tree model was developed in Microsoft EXCEL. Site and stage-specific treatment pathways were constructed from guidelines and validated by expert clinical opinion. Health care resource use associated with diagnosis, treatment and follow-up were obtained from the National Cancer Registry Ireland (n=1,498 cancers diagnosed during 2004-2005) and three local hospital databases (n=155, 142 and 46 cases diagnosed in 2007). Unit costs for hospitalisation, procedures, laboratory tests and radiotherapy were derived from DRG costs, hospital finance departments, clinical opinion and literature review. Chemotherapy costs were estimated from local hospital protocols, pharmacy departments and clinical opinion. Uncertainty was explored using one-way and probabilistic sensitivity analysis.

RESULTS

In 2008, the average (stage weighted) lifetime cost of managing a case of colorectal cancer was €39,607. Average costs were 16% higher for rectal (€43,502) than colon cancer (€37,417). Stage I disease was the least costly (€23,688) and stage III most costly (€48,835). Diagnostic work-up and follow-up investigations accounted for 4 and 5% of total costs, respectively. Cost estimates were most sensitive to recurrence rates and prescribing of biological agents.

CONCLUSION

This study demonstrates the value of using existing data from national and local databases in contributing to estimating the cost of managing cancer. The findings illustrate the impact of biological agents on costs of cancer care and the potential of strategies promoting earlier diagnosis to reduce health care resource utilisation and care costs.

The effectiveness of training and support for carers and other professionals on the physical and emotional health and well-being of looked-after children and young people: a systematic review

Looked-after children and young people (LACYP) are recognized as a high-risk group for behavioural and emotional problems, and additional specialist training for foster carers may reduce such problems. This systematic review aimed to identify and synthesize evidence on the effectiveness of additional training and support provided to approved carers, professionals and volunteers on the physical and emotional health and well-being of LACYP (including problem behaviours and placement stability). Searches of health and social science databases were conducted and records were screened for inclusion criteria. Citation and reference list searches were conducted on included studies. Included studies were synthesized and critically appraised. Six studies were included (five randomized controlled trials and one prospective cohort study), all of which focused on foster carers. Three studies reported a benefit of training and three reported no benefit but no detriment. Those reporting a benefit of training were conducted in the USA, and had longer-duration training, shorter follow-up assessment and recruited carers of younger children than studies that reported no benefit of training, which were conducted in the UK. Whether the difference in results is due to the type of training or to cultural or population differences is unclear. The findings suggest a mixed effect of training for foster carers on problem behaviours of LACYP. The evidence identified appears to suggest that longer-duration training programmes have a beneficial effect on the behaviour problems of LACYP, although future research should examine the impact of training durations and intensity on short-medium and longer-term outcomes of LACYP of different ages. Only training and support for foster carers was identified.

Cost-effectiveness of population-based screening for colorectal cancer: a comparison of guaiac-based faecal occult blood testing, faecal immunochemical testing and flexible sigmoidoscopy

BACKGROUND

Several colorectal cancer-screening tests are available, but it is uncertain which provides the best balance of risks and benefits within a screening programme. We evaluated cost-effectiveness of a population-based screening programme in Ireland based on (i) biennial guaiac-based faecal occult blood testing (gFOBT) at ages 55-74, with reflex faecal immunochemical testing (FIT); (ii) biennial FIT at ages 55-74; and (iii) once-only flexible sigmoidoscopy (FSIG) at age 60.

METHODS

A state-transition model was used to estimate costs and outcomes for each screening scenario vs no screening. A third party payer perspective was adopted. Probabilistic sensitivity analyses were undertaken.

RESULTS

All scenarios would be considered highly cost-effective compared with no screening. The lowest incremental cost-effectiveness ratio (ICER vs no screening euro 589 per quality-adjusted life-year (QALY) gained) was found for FSIG, followed by FIT euro 1696) and gFOBT (euro 4428); gFOBT was dominated. Compared with FSIG, FIT was associated with greater gains in QALYs and reductions in lifetime cancer incidence and mortality, but was more costly, required considerably more colonoscopies and resulted in more complications. Results were robust to variations in parameter estimates.

CONCLUSION

Population-based screening based on FIT is expected to result in greater health gains than a policy of gFOBT (with reflex FIT) or once-only FSIG, but would require significantly more colonoscopy resources and result in more individuals experiencing adverse effects. Weighing these advantages and disadvantages presents a considerable challenge to policy makers.

Supporting the transition of looked-after young people to independent living: a systematic review of interventions and adult outcomes

This systematic review aimed to synthesize evidence on the effectiveness of transition support services (TSSs) that are delivered towards the end of care for looked-after young people (LAYP) on their adult outcomes, including education, employment, substance misuse, criminal and offending behaviour, parenthood, housing and homelessness and health. Searches of health, social science and social care bibliographic databases were conducted and records were screened for relevance. Citation and reference list searches were conducted on included studies. Relevant studies were synthesized and critically appraised. Seven studies were identified (five retrospective and two prospective cohort studies), six of which were conducted in the USA and one in the UK. Overall, LAYP who received TSSs were more likely to complete compulsory education with formal qualifications, be in current employment, be living independently and less likely to be young parents. There was no reported effect of the impact of TSSs on crime or mental health, and mixed findings for homelessness. The range of TSS components investigated and reported varied considerably within and between studies, with limited evidence of long-term outcomes. The literature reviewed offers no reliable conclusions on the effectiveness of TSSs at this time due to variations in research quality and because few formal evaluations of existing TSSs have been conducted, resulting in mixed evidence in terms of positive, negative and neutral impact on outcomes. Further high-quality, robust research to evaluate the effectiveness of TSSs on adult outcomes for young people in the short, medium and longer term is needed to address the health inequalities experienced by this small but vulnerable group and to inform decision making about service provision.

Factors associated with outcomes for looked-after children and young people: a correlates review of the literature

In 2008, the Department of Health made a referral to the National Institute for Health and Clinical Excellence and the Social Care Institute for Excellence to develop joint public health guidance on improving the physical and emotional health and well-being of children and young people looked after by the local authority/state. To help inform the decision-making process by identifying potential research questions pertinent to the outcomes of looked-after children and young people (LACYP), a correlates review was undertaken. Iterative searches of health and social science databases were undertaken; searches of reference lists and citation searches were conducted and all included studies were critically appraised. The correlates review is a mapping review conducted using systematic and transparent methodology. Interventions and factors that are associated (or correlated) with outcomes for LACYP were identified and presented as conceptual maps. This review maps the breadth (rather than depth) of the evidence and represents an attempt to use the existing evidence base to map associations between potential risk factors, protective factors, interventions and outcomes for LACYP. Ninety-two studies were included: four systematic reviews, five non-systematic reviews, eight randomized controlled trials, 66 cohort studies and nine cross-sectional studies. The conceptual maps provide an overview of the key relationships addressed in the current literature, in particular, placement stability and emotional and behavioural factors in mediating outcomes. From the maps, there appear to be some key factors that are associated with a range of outcomes, in particular, number of placements, behavioural problems and age at first placement. Placement stability seems to be a key mediator of directional associations. The correlates review identified key areas where sufficient evidence to conduct a systematic review might exist. These were: transition support, training and support for carers and access to services.

Avoiding and identifying errors in health technology assessment models: qualitative study and methodological review

BACKGROUND

Health policy decisions must be relevant, evidence-based and transparent. Decision-analytic modelling supports this process but its role is reliant on its credibility. Errors in mathematical decision models or simulation exercises are unavoidable but little attention has been paid to processes in model development. Numerous error avoidance/identification strategies could be adopted but it is difficult to evaluate the merits of strategies for improving the credibility of models without first developing an understanding of error types and causes.

OBJECTIVES

The study aims to describe the current comprehension of errors in the HTA modelling community and generate a taxonomy of model errors. Four primary objectives are to: (1) describe the current understanding of errors in HTA modelling; (2) understand current processes applied by the technology assessment community for avoiding errors in development, debugging and critically appraising models for errors; (3) use HTA modellers' perceptions of model errors with the wider non-HTA literature to develop a taxonomy of model errors; and (4) explore potential methods and procedures to reduce the occurrence of errors in models. It also describes the model development process as perceived by practitioners working within the HTA community.

DATA SOURCES

A methodological review was undertaken using an iterative search methodology. Exploratory searches informed the scope of interviews; later searches focused on issues arising from the interviews. Searches were undertaken in February 2008 and January 2009. In-depth qualitative interviews were performed with 12 HTA modellers from academic and commercial modelling sectors.

REVIEW METHODS

All qualitative data were analysed using the Framework approach. Descriptive and explanatory accounts were used to interrogate the data within and across themes and subthemes: organisation, roles and communication; the model development process; definition of error; types of model error; strategies for avoiding errors; strategies for identifying errors; and barriers and facilitators.

RESULTS

There was no common language in the discussion of modelling errors and there was inconsistency in the perceived boundaries of what constitutes an error. Asked about the definition of model error, there was a tendency for interviewees to exclude matters of judgement from being errors and focus on 'slips' and 'lapses', but discussion of slips and lapses comprised less than 20% of the discussion on types of errors. Interviewees devoted 70% of the discussion to softer elements of the process of defining the decision question and conceptual modelling, mostly the realms of judgement, skills, experience and training. The original focus concerned model errors, but it may be more useful to refer to modelling risks. Several interviewees discussed concepts of validation and verification, with notable consistency in interpretation: verification meaning the process of ensuring that the computer model correctly implemented the intended model, whereas validation means the process of ensuring that a model is fit for purpose. Methodological literature on verification and validation of models makes reference to the Hermeneutic philosophical position, highlighting that the concept of model validation should not be externalized from the decision-makers and the decision-making process. Interviewees demonstrated examples of all major error types identified in the literature: errors in the description of the decision problem, in model structure, in use of evidence, in implementation of the model, in operation of the model, and in presentation and understanding of results. The HTA error classifications were compared against existing classifications of model errors in the literature. A range of techniques and processes are currently used to avoid errors in HTA models: engaging with clinical experts, clients and decision-makers to ensure mutual understanding, producing written documentation of the proposed model, explicit conceptual modelling, stepping through skeleton models with experts, ensuring transparency in reporting, adopting standard housekeeping techniques, and ensuring that those parties involved in the model development process have sufficient and relevant training. Clarity and mutual understanding were identified as key issues. However, their current implementation is not framed within an overall strategy for structuring complex problems.

LIMITATIONS

Some of the questioning may have biased interviewees responses but as all interviewees were represented in the analysis no rebalancing of the report was deemed necessary. A potential weakness of the literature review was its focus on spreadsheet and program development rather than specifically on model development. It should also be noted that the identified literature concerning programming errors was very narrow despite broad searches being undertaken.

CONCLUSIONS

Published definitions of overall model validity comprising conceptual model validation, verification of the computer model, and operational validity of the use of the model in addressing the real-world problem are consistent with the views expressed by the HTA community and are therefore recommended as the basis for further discussions of model credibility. Such discussions should focus on risks, including errors of implementation, errors in matters of judgement and violations. Discussions of modelling risks should reflect the potentially complex network of cognitive breakdowns that lead to errors in models and existing research on the cognitive basis of human error should be included in an examination of modelling errors. There is a need to develop a better understanding of the skills requirements for the development, operation and use of HTA models. Interaction between modeller and client in developing mutual understanding of a model establishes that model's significance and its warranty. This highlights that model credibility is the central concern of decision-makers using models so it is crucial that the concept of model validation should not be externalized from the decision-makers and the decision-making process. Recommendations for future research would be studies of verification and validation; the model development process; and identification of modifications to the modelling process with the aim of preventing the occurrence of errors and improving the identification of errors in models.

Docetaxel for the adjuvant treatment of early node-positive breast cancer: a single technology appraisal

This paper presents a summary of the evidence review group (ERG) report into the clinical and cost-effectiveness of docetaxel for the adjuvant treatment of early node-positive breast cancer based upon the manufacturer's submission to the National Institute for Health and Clinical Excellence (NICE) as part of the single technology appraisal (STA) process. The manufacturer's scope restricts the intervention to docetaxel in combination with doxorubicin and cyclophosphamide (TAC), and the comparator to anthracycline-based chemotherapy. Based on the BCIRG 001 trial, the submitted evidence shows that TAC is associated with superior disease-free and overall survival at 5 years compared with the anthracycline-based regimen FAC. The absolute risk reduction in patients treated with TAC compared with those treated with FAC was 7% for disease-free survival and 6% for overall survival. However, TAC was associated with significantly greater toxicity than FAC. There is also evidence that docetaxel, in an unlicensed sequential regimen FEC100-T, is associated with superior disease-free and overall survival at 5 years compared with FEC100. An economic model was developed by the manufacturer based on the BCIRG 001 trial. This generated central estimates of the cost per life-year gained and cost per quality-adjusted life-year (QALY) gained of TAC compared with FAC of 7900 pounds and 9800 pounds respectively. The manufacturer's submission predicts a cost-effectiveness of 15,000 pounds to 20,000 pounds per QALY gained for TAC compared with E-CMF (epirubicin in sequential therapy with cyclophosphamide, methotrexate, and fluorouracil), and estimates the cost-effectiveness of FEC100-T to be 8200 pounds per QALY compared with FEC100. Taking into account a number of issues identified by the ERG this may generate higher estimates of cost-effectiveness, but these are unlikely to exceed 35,000 pounds per QALY gained. Importantly, FAC is not commonly used in clinical practice in the UK and, therefore, the submitted evidence does not indicate whether TAC is superior to the anthracycline-based regimens that are in common use (FEC or E-CMF). The indirect comparisons presented suggest that the economic case for TAC in comparison to current UK practice may not be proven. The manufacturer's submission failed to record evidence of three serious adverse events in patients receiving docetaxel with doxorubicin or to mention the concern of the European Medicines Agency regarding TAC's long-term adverse events. The guidance issued by NICE in June 2006 as a result of the STA states that docetaxel, when given concurrently with doxorubicin and cyclophosphamide (the TAC regimen), is recommended as an option for the adjuvant treatment of women with early node-positive breast cancer.

Spinal cord stimulation for chronic pain of neuropathic or ischaemic origin: systematic review and economic evaluation

OBJECTIVES

This report addressed the question 'What is the clinical and cost-effectiveness of spinal cord stimulation (SCS) in the management of chronic neuropathic or ischaemic pain?'

DATA SOURCES

Thirteen electronic databases [including MEDLINE (1950-2007), EMBASE (1980-2007) and the Cochrane Library (1991-2007)] were searched from inception; relevant journals were hand-searched; and appropriate websites for specific conditions causing chronic neuropathic/ischaemic pain were browsed. Literature searches were conducted from August 2007 to September 2007.

REVIEW METHODS

A systematic review of the literature sought clinical and cost-effectiveness data for SCS in adults with chronic neuropathic or ischaemic pain with inadequate response to medical or surgical treatment other than SCS. Economic analyses were performed to model the cost-effectiveness and cost-utility of SCS in patients with neuropathic or ischaemic pain.

RESULTS

From approximately 6000 citations identified, 11 randomised controlled trials (RCTs) were included in the clinical effectiveness review: three of neuropathic pain and eight of ischaemic pain. Trials were available for the neuropathic conditions failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS) type I, and they suggested that SCS was more effective than conventional medical management (CMM) or reoperation in reducing pain. The ischaemic pain trials had small sample sizes, meaning that most may not have been adequately powered to detect clinically meaningful differences. Trial evidence failed to demonstrate that pain relief in critical limb ischaemia (CLI) was better for SCS than for CMM; however, it suggested that SCS was effective in delaying refractory angina pain onset during exercise at short-term follow-up, although not more so than coronary artery bypass grafting (CABG) for those patients eligible for that surgery. The results for the neuropathic pain model suggested that the cost-effectiveness estimates for SCS in patients with FBSS who had inadequate responses to medical or surgical treatment were below 20,000 pounds per quality-adjusted life-year (QALY) gained. In patients with CRPS who had had an inadequate response to medical treatment the incremental cost-effectiveness ratio (ICER) was 25,095 pounds per QALY gained. When the SCS device costs varied from 5000 pounds to 15,000 pounds, the ICERs ranged from 2563 pounds per QALY to 22,356 pounds per QALY for FBSS when compared with CMM and from 2283 pounds per QALY to 19,624 pounds per QALY for FBSS compared with reoperation. For CRPS the ICERs ranged from 9374 pounds per QALY to 66,646 pounds per QALY. If device longevity (1 to 14 years) and device average price (5000 pounds to 15,000 pounds) were varied simultaneously, ICERs were below or very close to 30,000 pounds per QALY when device longevity was 3 years and below or very close to 20,000 pounds per QALY when device longevity was 4 years. Sensitivity analyses were performed varying the costs of CMM, device longevity and average device cost, showing that ICERs for CRPS were higher. In the ischaemic model, it was difficult to determine whether SCS represented value for money when there was insufficient evidence to demonstrate its comparative efficacy. The threshold analysis suggested that the most favourable economic profiles for treatment with SCS were when compared to CABG in patients eligible for percutaneous coronary intervention (PCI), and in patients eligible for CABG and PCI. In these two cases, SCS dominated (it cost less and accrued more survival benefits) over CABG.

CONCLUSIONS

The evidence suggested that SCS was effective in reducing the chronic neuropathic pain of FBSS and CRPS type I. For ischaemic pain, there may need to be selection criteria developed for CLI, and SCS may have clinical benefit for refractory angina short-term. Further trials of other types of neuropathic pain or subgroups of ischaemic pain, may be useful.

Docetaxel for the adjuvant treatment of early nodepositive breast cancer: a single technology appraisal

This paper presents a summary of the evidence review group (ERG) report into the clinical and cost-effectiveness of docetaxel for the adjuvant treatment of early node-positive breast cancer based upon the manufacturer’s submission to the National Institute for Health and Clinical Excellence (NICE) as part of the single technology appraisal (STA) process. The manufacturer’s scope restricts the intervention to docetaxel in combination with doxorubicin and cyclophosphamide (TAC), and the comparator to anthracycline-based chemotherapy. Based on the BCIRG 001 trial, the submitted evidence shows that TAC is associated with superior disease-free and overall survival at 5 years compared with the anthracycline-based regimen FAC. The absolute risk reduction in patients treated with TAC compared with those treated with FAC was 7% for disease-free survival and 6% for overall survival. However, TAC was associated with significantly greater toxicity than FAC. There is also evidence that docetaxel, in an unlicensed sequential regimen FEC100-T, is associated with superior diseasefree and overall survival at 5 years compared with FEC100. An economic model was developed by the manufacturer based on the BCIRG 001 trial. This generated central estimates of the cost per life-year gained and cost per quality-adjusted lifeyear (QALY) gained of TAC compared with FAC of £7900 and £9800 respectively. The manufacturer’s submission predicts a cost-effectiveness of £15,000–£20,000 per QALY gained for TAC compared with E-CMF (epirubicin in sequential therapy with cyclophosphamide, methotrexate, and fluorouracil), and estimates the cost-effectiveness of FEC100-T to be £8200 per QALY compared with FEC100. Taking into account a number of issues identified by the ERG this may generate higher estimates of cost-effectiveness, but these are unlikely to exceed £35,000 per QALY gained. Importantly, FAC is not commonly used in clinical practice in the UK and, therefore, the submitted evidence does not indicate whether TAC is superior to the anthracycline-based regimens that are in common use (FEC or E-CMF). The indirect comparisons presented suggest that the economic case for TAC in comparison to current UK practice may not be proven. The manufacturer’s submission failed to record evidence of three serious adverse events in patients receiving docetaxel with doxorubicin or to mention the concern of the European Medicines Agency regarding TAC’s long-term adverse events. The guidance issued by NICE in June 2006 as a result of the STA states that docetaxel, when given concurrently with doxorubicin and cyclophosphamide (the TAC regimen), is recommended as an option for the adjuvant treatment of women with early nodepositive breast cancer.

Ezetimibe monotherapy for cholesterol lowering in 2,722 people: systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

To study the evidence on the efficacy and safety of ezetimibe monotherapy for the treatment of primary (heterozygous familial and non-familial) hypercholesterolaemia.

DESIGN

Systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

Eleven electronic bibliographic databases covering the biomedical, scientific and grey literature were searched from inception and supplemented by contact with experts in the field. Two reviewers independently determined the eligibility of RCTs, with a minimum treatment duration of 12 weeks, which compared ezetimibe monotherapy (10 mg per day) with placebo.

RESULTS

In the absence of data from clinical outcome trials, surrogate endpoints such as changes in lipid concentrations were used as indicators of clinical outcomes. A meta-analysis of eight randomized, double-blind, placebo-controlled trials (all 12 weeks) showed that ezetimibe monotherapy was associated with a statistically significant mean reduction in LDL cholesterol (from baseline to endpoint) of -18.58%, (95% CI: -19.67 to -17.48, P < 0.00001) compared with placebo. Significant (P < 0.00001) changes were also found in total cholesterol (-13.46%, 95% CI: -14.22 to -12.70), HDL cholesterol (3.00%, 95% CI: 2.06-3.94) and triglyceride levels (-8.06%, 95% CI: -10.92 to -5.20). Ezetimibe monotherapy appeared to be well tolerated with a safety profile similar to placebo.

CONCLUSIONS

In a meta-analysis restricted to short-term trials in hypercholesterolaemia, significant potentially favourable changes in lipid and lipoprotein levels relative to baseline occurred with ezetimibe monotherapy. Further long-term studies with cardiovascular and other clinical outcome data are needed to assess the efficacy and safety of ezetimibe more fully.

The pregnancy-induced increase in baseline circulating growth hormone in rats is not induced by ghrelin

The elevation in baseline circulating growth hormone (GH) that occurs in pregnant rats is thought to arise from increased pituitary GH secretion, but the underlying mechanism remains unclear. Distribution, Fourier and algorithmic analyses confirmed that the pregnancy-induced increase in circulating GH in 3-week pregnant rats was due to a 13-fold increase in baseline circulating GH (P < 0.01), without any significant alteration in the parameters of episodic secretion. Electron microscopy revealed that pregnancy resulted in a reduction in the proportion of mammosomatotrophs (P < 0.01) and an increase in type II lactotrophs (P < 0.05), without any significant change in the somatotroph population. However, the density of the secretory granules in somatotrophs from 3-week pregnant rats was reduced (P < 0.05), and their distribution markedly polarised; the granules being grouped nearest the vasculature. Pituitary GH content was not increased, but steady-state GH mRNA levels declined progressively during pregnancy (P < 0.05). In situ hybridisation revealed that pregnancy was accompanied by a suppression of GH-releasing hormone mRNA expression in the arcuate nuclei (P < 0.05) and enhanced somatostatin mRNA expression in the periventricular nuclei (P < 0.05), an expression pattern normally associated with increased GH feedback. Although gastric ghrelin mRNA expression was elevated by 50% in 3-week pregnant rats (P < 0.01), circulating ghrelin, GH-secretagogue receptor mRNA expression and the GH response to a bolus i.v. injection of exogenous ghrelin were all largely unaffected during pregnancy. Although trace amounts of 'pituitary' GH could be detected in the placenta with radioimmunoassay, significant GH-immunoreactivity could not be observed by immunohistochemistry, indicating that rat placenta itself does not produce 'pituitary' GH. Although not excluding the possibility that the pregnancy-associated elevation in baseline circulating GH could arise from alternative extra-pituitary sources (e.g. the ovary), our data indicate that this phenomenon is most likely to result from a direct alteration of somatotroph function.

Cost-effectiveness of oxaliplatin and capecitabine in the adjuvant treatment of stage III colon cancer

For many years, the standard treatment for stage III colon cancer has been surgical resection followed by 5-fluorouracil in combination with folinic acid (5-FU/LV). Ongoing clinical trial evidence suggests that capecitabine and oxaliplatin (in combination with 5-FU/LV) may improve disease-free survival and overall survival when compared against 5-FU/LV alone in the adjuvant setting. This study evaluates the cost-effectiveness profiles of these two regimens in comparison to standard chemotherapy, using evidence from two international randomised controlled trials. Survival modelling techniques were employed to extrapolate survival curves from the two trials in order to estimate the long-term benefits of alternative treatment options over the remaining lifetime of patients. The health economic analysis suggests that capecitabine is expected to produce greater health gains at a lower cost than 5-FU/LV. Oxaliplatin in combination with 5-FU/LV is estimated to cost pounds 2970 per additional QALY gained when compared to 5-FU/LV alone. Future research should attempt to elucidate uncertainties concerning the optimal roles of capecitabine and/or oxaliplatin in the adjuvant setting in order to achieve the maximum level of clinical benefit.

Systematic review and economic evaluation of a long-acting insulin analogue, insulin glargine

OBJECTIVES

To evaluate the use of insulin glargine in its licensed basal-bolus indication in terms of both clinical and cost-effectiveness.

DATA SOURCES

Electronic databases.

REVIEW METHODS

A systematic review of the literature, involving a range of databases, was performed to identify all papers relating to insulin glargine.

RESULTS

Nineteen studies met the inclusion criteria but full reports were available for only six. For type 1 diabetes patients, insulin glargine appears to be more effective than neutral protamine Hagedorn (NPH) in reducing fasting blood glucose (FBG) but not in reducing glycosylated haemoglobin (HbA1c) and there is some evidence that both insulins are as effective as each other in both FBG and HbA1c control. For type 2 patients for whom oral antidiabetic agents provide inadequate glycaemic control, there is no evidence that insulin glargine is more effective than NPH in reducing either FBG or HbA1c and some evidence that both insulins are as effective as each other in both FBG and HbA1c control. Evidence for control of hypoglycaemia is equivocal. In studies where insulin glargine is demonstrated to be superior to NPH in controlling nocturnal hypoglycaemia, this may be only apparent when compared with once-daily NPH and not twice-daily NPH. Further, this superiority of glargine over NPH in the control of nocturnal hypoglycaemia may relate to one formulation of insulin glargine (HOE901[80]) and not another (HOE901[30]). There is no conclusive evidence that insulin glargine is superior to NPH in controlling symptomatic hypoglycaemia and severe hypoglycaemia. Insufficient data are available to conclude whether insulin glargine is different from each of the commonly used NPH dosing regimens: once daily and more than once daily. Given the lack of a published evidence base for the cost-effectiveness of insulin glargine, the economic review concentrates on a review of the industry submission and an amended model. Three economic models are provided in the submission, two relating to type 1 diabetes and one relating to type 2 diabetes. All three models compare the cost--utility of insulin glargine against NPH insulin. In general, the structures of the models are poor and in all three models, mistakes relating to assumptions and calculations have been made. The assessment team believe that the cost per QALY estimates generated by the Aventis model may be an underestimate for several reasons. The cost-effectiveness of insulin glargine in both type 1 and type 2 diabetes is highly sensitive to the amount of utility associated with reducing the fear of hypoglycaemia.

CONCLUSIONS

The evidence suggests that, compared with NPH insulin, insulin glargine is effective in reducing the number of nocturnal hypoglycaemic episodes, especially when compared with once-daily NPH. There appears to be no improvement in long-term glycaemic control and therefore insulin glargine is unlikely to reduce the incidence of the long-term microvascular and cardiovascular complications of diabetes. Further research into insulin glargine is needed that addresses the quality of life issues associated with fear of hypoglycaemia and also the economic impact of balance of HbA1c control and incidence of hypoglycaemia achieved in practice. Studies examining the economic evidence on insulin glargine should be published.

Clinical effectiveness and cost-effectiveness of pioglitazone and rosiglitazone in the treatment of type 2 diabetes: a systematic review and economic evaluation

OBJECTIVES

To evaluate the use of pioglitazone and rosiglitazone, in terms of both clinical and cost-effectiveness in the treatment of type 2 diabetes.

DATA SOURCES

Electronic databases and the reference lists of relevant articles, in addition 14 health services research-related resources were consulted via the Internet.

REVIEW METHODS

A systematic review of the literature, involving a range of databases, was performed to identify all papers relating to the glitazones. The methodological quality of the included randomised controlled trials (RCTs) was assessed using the Jadad method. A generic proforma for the critical appraisal of modelling studies in health economics was used in systematically reviewing the economic assessment studies identified. This was supplemented by a detailed review of the disease-specific factors within the studies. Where possible, key outcomes were compared. Readers should note that information from the sponsor's submission was submitted in confidence to the National Institute for Clinical Excellence (NICE). Such information was made available to the NICE Appraisals Committee, but has been removed from this version of the report.

RESULTS

Of the 1272 studies identified, nine studies met the inclusion criteria. The clinical evidence available showed that glitazones reduce glycosylated haemoglobin by approximately 1%, and are more effective at higher doses than at lower doses. Glitazone treatment is associated with weight gain. No published data were available on the long-term effects of glitazone use. No prospective RCTs were found comparing pioglitazone to rosiglitazone, but the available evidence indicated that the two treatments had similar effects. There are no published economic studies on either pioglitazone or rosiglitazone. Economic evaluations for both glitazones were provided by the manufacturers. Sensitivity analyses undertaken by the assessment team suggest that the cost per quality-adjusted life-year (QALY) of rosiglitazone is most sensitive to dosage and treatment effect, that is, the effect of rosiglitazone on beta-cell function and insulin sensitivity. In the two scenarios where rosiglitazone is compared with metformin and sulfonylurea combination therapy, the cost-effectiveness of rosiglitazone switches from around 10,000 pounds per QALY to being dominated by the comparator strategy. Since the baseline estimate of cost-effectiveness is not robust to changes in the treatment effect and is reliant on the many assumptions included within the metabolic and long-term economic models, caution should be used in interpreting the baseline result.

CONCLUSIONS

The clinical evidence available showed that glitazones can reduce glycosylated haemoglobin; however there were no peer-reviewed data available on the long-term effects of their use or any prospective RCTs found comparing pioglitazone with rosiglitazone. No published economic studies on either pioglitazone or rosiglitazone were found, although sensitivity analyses undertaken by the assessment team suggest that the cost per QALY of rosiglitazone is most sensitive to dosage and treatment effect. It is suggested that research already undertaken in this area should be published, preferably in peer-reviewed journals. Direct head-to-head comparisons of the glitazones in combination with metformin or sulfonylurea would be helpful. The current licence arrangements do not allow for routine use of the glitazones in triple oral combination therapy or in combination with insulin. Evidence is emerging of use of the glitazones within such combinations; therefore, prospective RCTs would be useful. These studies could examine short-term transition strategies and longer term management. The impact of the glitazones in delaying transfer to insulin and the impact on long-term outcomes should also be considered for investigation.

Liquid-based cytology in cervical screening: an updated rapid and systematic review and economic analysis

OBJECTIVES

To update an earlier published report reviewing the effectiveness and cost-effectiveness of liquid-based cytology (LBC).

DATA SOURCES

Electronic bibliographic databases, relevant articles, sponsor submissions and various health services research-related resources.

REVIEW METHODS

The selected data were reviewed and assessed with respect to the quality of the evidence. Pooled estimates of the parameters of interest were derived from the original and the updated studies. Meta-analyses were undertaken where appropriate. The mathematical model developed for the original rapid review of LBC was adapted to synthesise the updated data to estimate costs, survival and quality-adjusted survival of patients tested using LBC and using Papanicolaou (Pap) smear testing. Cost data from published sources were incorporated into the above model to allow economic, as well as clinical, implications of treatment to be assessed. The primary incremental cost-effectiveness ratio is the cost per life year gained (LYG), although estimates of the cost per quality-adjusted life-year (QALY) gained are also presented. A sensitivity analysis was undertaken to identify the key parameters that determine the cost-effectiveness of the treatments, with the objective of identifying how robust the results of the economic analysis are, given the current level of evidence.

RESULTS

From the evidence available, it is likely that the LBC technique will reduce the number of false-negative test results. Modelling analyses undertaken as part of this study indicate that this would reduce the incidence of invasive cancer. There is now more evidence to support improvements emanating from the use of LBC screening in terms of a reduced number of unsatisfactory specimens and a decrease in the time needed to obtain the smear samples. The estimated annual gross cost of consumables and operating equipment, and other one-off conversion costs associated with introducing the new technique, will be between 17 British pounds and 38 British pounds million in England and Wales, depending on the LBC system and the configuration of the service. Analyses based on models of disease natural history, conducted in this study, showed that conventional Pap smear screening was extendedly dominated by LBC (LBC was always more cost-effective than conventional Pap smear testing over the same screening interval). Comparing LBC across alternative screening intervals gave a cost-effectiveness of under 10,000 British pounds per LYG when screening was undertaken every 3 years. The cost-effectiveness results were relatively stable under most conditions, although if screening outcomes such as borderline results and colposcopy are assumed to induce even small amounts of disutility then LBC screening at 5-yearly intervals may be the most cost-effective option.

CONCLUSIONS

This updated analysis provides more certainty with regard to the potential cost-effectiveness of LBC compared with conventional Pap smear testing. However, there is uncertainty regarding the relative effectiveness (and cost-effectiveness) of the two main LBC techniques. Further research in the area of utility assessment may be worthwhile and possibly a full cost-effectiveness study of LBC based on a trial of its introduction in a low-prevalence population, although the results of the modelling analysis provide a robust argument that LBC is a cost-effective alternative to conventional cervical cancer screening. A randomised comparison of the two main techniques may also be useful.

A systematic review and economic evaluation of magnetic resonance cholangiopancreatography compared with diagnostic endoscopic retrograde cholangiopancreatography

OBJECTIVES

To compare the clinical and cost-effectiveness of magnetic resonance cholangiopancreatography (MRCP) with diagnostic endoscopic retrograde cholangiopancreatography (ERCP) for the investigation of biliary obstruction.

DATA SOURCES

Electronic bibliographic databases, the reference lists of relevant articles and various health services research-related resources.

REVIEW METHODS

The data sources were searched and selected studies were assessed using quality criteria. In total, 28 prospective diagnostic studies were identified reporting several suspected conditions plus one of patient satisfaction. Analyses were then performed to establish sensitivities, specificities, likelihood ratios and confidence intervals. The relative cost-effectiveness of adopting MRCP scanning in the investigation of the biliary tree was undertaken using a probabilistic economic model.

RESULTS

The median sensitivity for choledocholithiasis (13 studies) was 93% and the median specificity 94%. The median likelihood ratio for a positive value was 15.75 and for a negative value 0.08. Reported sensitivities for malignancy were somewhat lower, ranging from 81 to 86%, and specificities ranged from 92 to 100%. There was some evidence that MRCP is an accurate diagnostic test in comparison to ERCP, although the quality of studies was moderate. Claustrophobia prevented at least some patients from having MRCP in ten of the 28 studies. The other 18 studies did not mention claustrophobia. The probability of avoiding unnecessary diagnostic ERCP is estimated at 30%. These patients could avoid the unnecessary risk of complications and death associated with diagnostic ERCP, and substantial cost saving would be gained. The overall expected cost saving associated with MRCP is GBP149; the overall expected gain in quality-adjusted life-year is estimated at 0.011.

CONCLUSIONS

There is some evidence that MRCP is an accurate investigation compared with diagnostic ERCP, although the values for malignancy compared with choledocholithiasis were somewhat lower. The quality of studies was moderate. The limited evidence on patient satisfaction showed that patients preferred MRCP to diagnostic ERCP. The estimated clinical and economic impacts of diagnostic MRCP versus diagnostic ERCP are very favourable. The baseline estimate is that MRCP may both reduce cost and result in improved quality of life outcomes compared with diagnostic ERCP. Further research is suggested to compare MRCP and diagnostic ERCP with final diagnosis and also with the full range of target conditions; to examine patient satisfaction and ways of reducing problems with claustrophobia; to look at protocols to help identify who could most benefit from MRCP or ERCP; to assess the relative need and urgency of patient access to magnetic resonance imaging services, and also to determine how demand would affect availability and potential cost savings.

Clinical effectiveness and cost-effectiveness of neonatal screening for inborn errors of metabolism using tandem mass spectrometry: a systematic review

OBJECTIVES

To evaluate the clinical and cost-effectiveness of tandem mass spectrometry (MS)-based neonatal screening for inborn errors of metabolism (IEM).

DATA SOURCES

Fourteen electronic bibliographic databases covering biomedical, science, economic and grey literature, the reference lists of relevant articles and abstracts of conference proceedings and 18 health services research-related resources.

REVIEW METHODS

This review is an update of two previous HTA reports of neonatal screening for IEM. These reports have been updated by a systematic review of published research (between 1995 and January 2002) on neonatal screening of inherited metabolic disorders using tandem MS. This was supplemented by a search for economic literature and the application of a modelling exercise to investigate the economics of using tandem MS within a neonatal screening programme in the UK.

RESULTS

Evidence from the reviews of IEM found that the UK screening programme for phenylketonuria (PKU) was well established and there was universal agreement that neonatal screening for PKU was justified. Of the many other disorders that can be detected by tandem MS, the best candidate condition for a new screening programme was medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency. For many other IEM that can be detected by tandem MS, robust clinical evidence was limited. Cost-effectiveness analysis using economic modelling indicated that substituting the use of tandem MS for existing technologies for the screening of PKU alone could not be justified. However, results from the economic modelling indicate that the addition of screening for MCAD deficiency as part of a neonatal screening programme for PKU using tandem MS would be economically attractive. Using an operational range of 50,000-60,000 specimens per system per year, the mean incremental cost for PKU and MCAD deficiency screening combined using tandem MS from the model was -23,312 British pounds for each cohort of 100,000 neonates screened. This cost saving is associated with a mean incremental gain of 59 life-years. Additional economic modelling using the available evidence does not support including other inherited metabolic diseases within a neonatal screening programme at present.

CONCLUSIONS

The evidence appears to support the introduction of tandem MS into a UK neonatal screening programme for PKU and MCAD deficiency combined. Tandem MS has the potential for simultaneous multi-disease screening using a single analytical technique. Although the marginal cost of extending the programme to include other conditions may be relatively small, the application of this new technology to PKU and MCAD deficiency screening does not imply the wholesale inclusion of all disorders detectable by tandem MS. It is suggested that the primary focus of further research should be on the long-term effectiveness of treatment strategies on adverse outcomes (disabilities and impairments) under conventional management and the potential impact of early diagnosis using tandem MS.

The clinical and cost-effectiveness of pulsatile machine perfusion versus cold storage of kidneys for transplantation retrieved from heart-beating and non-heart-beating donors

OBJECTIVES

To evaluate the clinical and cost-effectiveness of machine perfusion (MP) compared to cold storage (CS), as a means of preserving kidneys prior to transplantation. Transplantation of kidneys from both heart-beating donors (HBDs) and non-heart-beating donors (NHBDs) is considered. Finally to review whether the use of MP can allow valid testing of kidney viability prior to transplantation.

DATA SOURCES

Fifteen electronic bibliographic databases were searched. The reference lists of relevant articles and sponsor submissions were hand searched and various health service research-related resources were consulted via the Internet.

REVIEW METHODS

A literature search was undertaken to identify relevant studies and a meta-analysis performed on the studies that had appropriate comparator groups and reported sufficient data. A structured review examined tests of viability of kidneys on MP. Economic modelling was used to determine the cost-effectiveness and cost-utility of MP.

RESULTS

The meta-analysis suggested that the use of MP, as compared with CS, is associated with a relative risk of delayed graft function (DGF) of 0.804 (95% confidence limits 0.672 to 0.961). There was no evidence to suggest that this effect is different in kidneys taken from HBDs as opposed to NHBDs. Meta-analysis of 1-year graft survival data showed no significant effect, but the studies, even when aggregated, were severely underpowered with respect to the likely impact on graft survival. The size of effects demonstrated were in line with those predicted by an indirect model of graft survival based on the association of DGF with graft loss. The economic assessment indicated that it is unlikely that in the UK health setting complete cost recovery will be obtained from a reduction in the incidence of DGF. The probability that MP is cheaper and more effective than CS in the long term was estimated at around 80% for NHBD recipients and 50-60% for HBD recipients. Flow characteristics of the perfusate of kidneys undergoing MP may be an indicator of kidney viability, but data were inadequate to calculate the sensitivity and specificity of any test based on this. The concentration of alpha-glutathione-S-transferase (a marker of cell damage) in the perfusate may be the basis of a valid test. A threshold of 2800 micrograms/100 g gave a sensitivity of 93% and specificity of 33% (and hence a likelihood ratio of 1.41).

CONCLUSIONS

The baseline analysis indicated that in the long-term MP would be expected to be cheaper and more effective than CS for both HBD and NHBD recipients. A definitive study of the clinical benefit of MP in order to establish its effect on DGF and longer term graft survival would be valuable, together with an economic evaluation of the benefits. While direct evidence relating to improvements in graft survival would be preferable, the small predicted improvement indicates that a very large sample size would be required. In addition to seeking direct evidence of the impact on DGF, research quantifying the impact of DGF on graft survival in this technology is required. Research is also needed to establish whether a valid test (or combination of tests) of kidney viability can be developed.

The role of modelling in prioritising and planning clinical trials

OBJECTIVES

To identify the role of modelling in planning and prioritising trials. The review focuses on modelling methods used in the construction of disease models and on methods for their analysis and interpretation.

DATA SOURCES

Searches were initially developed in MEDLINE and then translated into other databases.

REVIEW METHODS

Systematic reviews of the methodological and case study literature were undertaken. Search strategies focused on the intersection between three domains: modelling, health technology assessment and prioritisation.

RESULTS

The review found that modelling can extend the validity of trials by: generalising from trial populations to specific target groups; generalising to other settings and countries; extrapolating trial outcomes to the longer term; linking intermediate outcome measures to final outcomes; extending analysis to the relevant comparators; adjusting for prognostic factors in trials; and synthesising research results. The review suggested that modelling may offer greatest benefits where the impact of a technology occurs over a long duration, where disease/technology characteristics are not observable, where there are long lead times in research, or for rapidly changing technologies. It was also found that modelling can inform the key parameters for research: sample size, trial duration and population characteristics. One-way, multi-way and threshold sensitivity analysis have been used in informing these aspects but are flawed. The payback approach has been piloted and while there have been weaknesses in its implementation, the approach does have potential. Expected value of information analysis is the only existing methodology that has been applied in practice and can address all these issues. The potential benefit of this methodology is that the value of research is directly related to its impact on technology commissioning decisions, and is demonstrated in real and absolute rather than relative terms; it assesses the technical efficiency of different types of research. Modelling is not a substitute for data collection. However, modelling can identify trial designs of low priority in informing health technology commissioning decisions.

CONCLUSIONS

Good practice in undertaking and reporting economic modelling studies requires further dissemination and support, specifically in sensitivity analyses, model validation and the reporting of assumptions. Case studies of the payback approach using stochastic sensitivity analyses should be developed. Use of overall expected value of perfect information should be encouraged in modelling studies seeking to inform prioritisation and planning of health technology assessments. Research is required to assess if the potential benefits of value of information analysis can be realised in practice; on the definition of an adequate objective function; on methods for analysing computationally expensive models; and on methods for updating prior probability distributions.

The cost-effectiveness of nCPAP treatment in patients with moderate-to-severe obstructive sleep apnoea

The demand for diagnostic and therapeutic services for obstructive sleep apnoea syndrome (OSAS) showed marked growth during the 1990s. This paper analyses the long-term cost-effectiveness of nasal continuous positive airway pressure (nCPAP) treatment in comparison to conventional null treatment. A Markov model was used to represent the natural history of OSAS based upon published evidence. Utility values came from a survey of OSAS patients. Data on health costs were collected from hospitals in the Basque Country, Spain. The incremental cost-effectiveness ratio of nCPAP treatment is <6,000 Euros per quality-adjusted life year. On disaggregated analysis, nCPAP treatment accounts for 86% of incremental costs; 84% of incremental effectiveness is attributable to improved quality of life. Treatment of obstructive sleep apnoea syndrome with nasal continuous positive airway pressure has a cost-effectiveness that is in line with that of other commonly funded treatments such as antihypertensive drugs. The key clinical benefit of nasal continuous positive airway pressure treatment is improvement in the quality of life of patients with obstructive sleep apnoea syndrome. This benefit is also precisely the one for which the evidence base is strongest. The remaining uncertainties concerning the impact of nasal continuous positive airway pressure on long-term mortality have only a relatively small impact on the economics of treatment.

A systematic review of the clinical effectiveness of pioglitazone in the treatment of type 2 diabetes mellitus

BACKGROUND

Pioglitazone is a member of a recently developed class of glucose-lowering agents, the thiazolidinediones, used in the treatment of type 2 diabetes mellitus. In the United States, it is approved for use both as monotherapy and in combination with metformin, a sulfonylurea, or insulin; in Europe, it is approved for use in combination with metformin or a sulfonylurea but not insulin.

OBJECTIVE

This article presents a systematic review of the published literature on the effectiveness of pioglitazone in the treatment of type 2 diabetes, both as monotherapy and in combination with other antidiabetic agents.

METHODS

The peer-reviewed English- and foreign-language literature was searched using MEDLINE, PubMED, EMBASE, Science Citation Index, the Cochrane Database of Systematic Reviews, the Cochrane Controlled Trials Register, the UK National Health Service Centre for Reviews and Dissemination databases, and the Office of Health Economics Health Economic Evaluations Database. Searches were not limited to specific publication types, study designs, dates, or languages. The latest search was performed in March 2001. For a trial to be included in the review, at least 1 outcome measure had to involve the effects of pioglitazone on glycemic control or cardiovascular risk factors, or its side effects. Because of the heterogeneity of studies, no formal meta-analysis was performed.

RESULTS

Eleven studies met the inclusion criteria, 6 involving pioglitazone monotherapy and 5 involving combination therapy. Full reports were available for only 6 of the 11 studies. No studies directly compared pioglitazone with other antidiabetic drugs. Both as monotherapy and in combination therapy, pioglitazone produced decreases in blood glucose levels (up to 95 mg/dL) and glycosylated hemoglobin (up to 2.6%). At doses of > or = 30 mg/d, pioglitazone was associated with reductions in triglyceride levels (-30-70 mg/dL) and increases in high-density lipoprotein cholesterol (HDL-C) levels (-4-5 mg/dL). Pioglitazone treatment was associated with significant weight gain (up to 4 kg over 16 weeks). Adverse effects included mild edema (in up to 11.7% of patients) and a clinically nonsignificant decrease in hemoglobin concentrations. Abnormal results on liver function testing were no more common in treated patients than in control groups.

CONCLUSIONS

Pioglitazone has been shown to reduce blood glucose levels in patients with type 2 diabetes. Although the observed decreases in triglyceride levels and increases in HDL-C levels could be expected to lead to a reduction in cardiovascular risk, the effects of weight gain may counteract this benefit. The evidence suggests that the preferred role for pioglitazone may be as an adjunct to metformin or a sulfonylurea in patients whose condition is not well controlled with monotherapy and for whom a metformin-sulfonylurea combination is contraindicated. There is a need for large-scale, long-term studies comparing the effectiveness of combination therapy that includes pioglitazone with that of other combinations of antidiabetic drugs.

Structure-activity relationship investigations of a potent and selective benzodiazepine oxytocin antagonist

We have investigated the structure-activity relationships of the 1- and 3-substituents and replacements of the 5-phenyl group of GW405212X 1, a potent selective oxytocin antagonist. The effect of these modifications on oxytocin binding antagonism and on pharmacokinetic parameters is reported.