The price of precision: trade-offs between usability and validity in the World Health Organization Health Economic Assessment Tool for walking and cycling.

OBJECTIVES: The widely used World Health Organization (WHO) Health Economic Assessment Tool (HEAT) for walking and cycling quantifies health impacts in terms of premature deaths avoided or caused as a result of changes in active transport. This article attempts to assess the effect of incorporating 'life-years' as an impact measure to increase the precision of the model and assess the effect on the tool's usability. STUDY DESIGN: This article is a methods paper, using simulation to estimate the effect of a methodological change to the HEAT 4.2 physical activity module. METHODS: We use the widely used WHO HEAT for walking and cycling as a case study. HEAT currently quantifies health impacts in terms of premature deaths avoided or caused as a result of changes in active transport. We assess the effect of incorporating "duration of life gained" as an impact measure to increase the precision of the model without substantially affecting usability or increasing data requirements. RESULTS: Compared with the existing tool (HEAT version 4.2), which values premature deaths avoided, estimates derived by valuing life-years gained are more sensitive to the age of the population affected by an intervention, with results for older and younger age groups being markedly different between the two methods. This is likely to improve the precision of the tool, especially where it is applied to interventions that affect age groups differentially. The life-years method requires additional background data (obtained and used in this analysis) and minimal additional user inputs; however, this may also make the tool harder to explain to users. CONCLUSIONS: Methodological improvements in the precision of widely used tools, such as the HEAT, may also inadvertently reduce their practical usability. It is therefore important to consider the overall impact on the tool's value to stakeholders and explore ways of mitigating potential reductions in usability.

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.

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.

Systematic review of the efficacy of cilostazol, naftidrofuryl oxalate and pentoxifylline for the treatment of intermittent claudication.

BACKGROUND: A systematic review and network meta-analysis was undertaken to consider the evidence for the efficacy and tolerability of placebo, cilostazol, naftidrofuryl oxalate and pentoxifylline in patients with intermittent claudication due to peripheral arterial disease (PAD). METHODS: MEDLINE, Embase, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Conference Proceedings, BIOSIS, National Research Register and MetaRegister databases were searched. Eligible studies were randomized controlled trials (RCTs) and published systematic reviews of patients with intermittent claudication due to PAD and whose symptoms persisted despite a period of conservative management. Study selection was conducted by one reviewer with involvement from a clinician. Data were extracted by one reviewer with no blinding to authors or journal, and checked by a second reviewer. Outcome measures were maximum walking distance (MWD) and pain-free walking distance (PFWD). RESULTS: The review identified 1876 citations; 26 RCTs met the inclusion criteria for the systematic review. Eleven trials provided data relevant for the meta-analysis. Naftidrofuryl oxalate was ranked first for both MWD and PFWD (probability of 0·947 and 0·987, respectively, of being the best treatment) followed by cilostazol and pentoxifylline. For naftidrofuryl oxalate, cilostazol and pentoxifylline, MWD increased by 60 (95 per cent credible interval 20 to 114) per cent, 25 (11 to 40) per cent and 11 (-1 to 24) per cent respectively relative to placebo, and PFWD increased by 49, 13 and 9 per cent. CONCLUSION: Naftidrofuryl oxalate and cilostazol are both effective treatments for claudication; naftidrofuryl oxalate is likely to be the most effective, with minimal serious adverse events.

Antioxidants in the chemoprevention of colorectal cancer and colorectal adenomas in the general population: a systematic review and meta-analysis.

AIM: Antioxidants, such as vitamin A, C and E, selenium and ß-carotene, have been proposed as possible agents in the chemoprevention of colorectal cancer and have been the subject of recent trials and reviews. This review aimed to assess the present evidence on the effect of antioxidants on the incidence of colorectal neoplasms in the general population. METHOD: A systematic review of randomized controlled trials was undertaken comparing antioxidants alone or in combination with other agents vs placebo. The following databases were searched for published and unpublished literature: Cochrane Library, MEDLINE, PreMEDLINE, CINAHL, EMBASE, Web of Science, and Biological Abstracts and Research Registers. Studies were quality appraised and extracted. Meta-analysis was performed. RESULTS: Twelve studies were identified as relevant. In the nine comparing antioxidants with no antioxidants (n=148 922), there was no difference in the incidence of colorectal cancer [relative risk (RR) 1.00, 95% confidence interval (CI) 0.88-1.13]. One study assessed the effect of antioxidants on adenoma formation (n=15 538) and did not demonstrate a statistically significant effect (RR 1.47, 95% CI 0.97-2.23). Of 14 discrete analyses for different combinations of antioxidants, only one reported a statistically significant increase in relative risk of adenoma formation in participants receiving vitamin E (RR 1.74, 95% CI 1.09-1.79, P=0.02) or vitamin E plus ß-carotene (RR 1.63, 95% CI 1.01-2.63, P=0.04). Effectiveness did not seem to differ between healthy populations, participants with cardiovascular risk factors or populations exposed to smoking or asbestos. CONCLUSION: The review demonstrates that antioxidants (vitamin A, C and E, selenium and ß-carotene), as single agents, in combination with other antioxidants or in combination with other agents, are not effective in the chemoprevention of colorectal neoplasia in the general population. This questions their involvement in future randomized controlled trials of chemoprevention in colorectal cancer.

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.

A systematic review and economic evaluation of cilostazol, naftidrofuryl oxalate, pentoxifylline and inositol nicotinate for the treatment of intermittent claudication in people with peripheral arterial disease.

BACKGROUND: Peripheral arterial disease (PAD) is a condition in which there is blockage or narrowing of the arteries that carry blood to the legs and arms. It is estimated to affect around 4.5% of people aged between 55 and 74 years within the UK. The most common symptom of PAD is intermittent claudication (IC), characterised by pain in the legs on walking that is relieved with rest. OBJECTIVE: To assess the effectiveness and cost-effectiveness of cilostazol, naftidrofuryl oxalate, pentoxifylline and inositol nicotinate, compared with no vasoactive drugs, for IC due to PAD in adults whose symptoms continue despite a period of conventional management. DATA SOURCE: Electronic bibliographic databases were searched during April to June 2010 (MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, The Cochrane Library databases, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Conference Proceedings Citation Index, BIOSIS Previews). REVIEW METHODS: Effectiveness outcomes sought were maximal walking distance (MWD), pain-free walking distance (PFWD), ankle-brachial pressure index, cardiovascular events, mortality, adverse events (AEs) and health-related quality of life (HRQoL). A narrative synthesis was provided for all outcomes and a network meta-analysis was undertaken for the walking distance outcomes. A Markov model was developed to assess the relative cost-effectiveness of the interventions from a NHS perspective over a lifetime. The model has three states: vasoactive drug treatment, no vasoactive drug treatment and death. Each 1-week cycle, patients may continue with the drug, discontinue the drug or die. Regression analysis was undertaken to model the relationship between MWD and utility so that a cost per quality-adjusted life-year (QALY) outcome measure could be presented. Univariate and probabilistic sensitivity analyses were undertaken. All costs and outcomes were discounted at 3.5%. RESULTS: Twenty-six randomised controlled trials were identified that met the inclusion criteria for the clinical effectiveness review. There was evidence that walking distance outcomes were significantly improved by both cilostazol and naftidrofuryl oxalate; the 95% credible intervals for the difference from placebo in the logarithm mean change MWD from baseline were 0.108 to 0.337 and 0.181 to 0.762, respectively. It was not possible to include inositol nicotinate within the meta-analysis of MWD and PFWD owing to the lack of 24-month data; however, the shorter-term data did not suggest a significant effect. AEs were minor for all drugs and included headaches and gastrointestinal difficulties. The incidence of serious adverse events (SAEs), including cardiovascular events and mortality, was not increased by the vasoactive drugs compared with placebo; however, most studies had a relatively short follow-up time to address this outcome. HRQoL data were limited. Two studies of limited quality were identified within the review of cost-effectiveness. The de novo model developed suggests that naftidrofuryl oxalate dominates cilostazol and pentoxifylline and has a cost per QALY gained of around £6070 compared with no vasoactive drug. This result is reasonably robust to changes within the key model assumptions. Inositol nicotinate was not included within the main analysis owing to lack of data. However, it is unlikely to be considered to be cost-effective due to its high acquisition cost (£900 vs £100-500 per year for the other drugs). CONCLUSIONS: Naftidrofuryl oxalate and cilostazol both appear to be effective treatments for this patient population, with minimal SAEs. However, naftidrofuryl oxalate is the only treatment that is likely to be considered cost-effective. The long-term effectiveness is uncertain and hence a trial comparing cilostazol, naftidrofuryl oxalate and placebo beyond 24 weeks would be beneficial. Outcomes associated with naftidrofuryl oxalate could also be compared with those associated with supervised exercise programmes and angioplasty.

Chemoprevention of colorectal cancer: systematic review and economic evaluation.

BACKGROUND: Colorectal cancer (CRC) is the third most common cancer in the UK: incidence increases with age, median age at diagnosis being over 70 years. Approximately 25% of cases occur in individuals with a family history of CRC, including 5% caused by familial adenomatous polyposis (FAP) or hereditary non-polyposis CRC (HNPCC). Most develop from adenomatous polyps arising from the intestine lining. Individuals with these polyps undergo polypectomy and are invited for endoscopic surveillance. Screening via faecal occult blood testing has been rolled out across the UK. OBJECTIVES: To evaluate the clinical effectiveness and cost-effectiveness of drug and micronutrient interventions for the prevention of CRC and/or adenomatous polyps. Interventions considered include: non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin and cyclo-oxygenase-2 (COX-2) inhibitors; folic acid; calcium; vitamin D and antioxidants (including vitamin A, vitamin C, vitamin E, selenium and beta-carotene). Chemoprevention was assessed in the general population, in individuals at increased risk of CRC, and in individuals with FAP or HNPCC. DATA SOURCES: A systematic review identified randomised controlled trials (RCTs) assessing drug and nutritional agents for the prevention of CRC or adenomatous polyps. A separate search identified qualitative studies relating to individuals' views, attitudes and beliefs about chemoprevention. MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, CINAHL, the Cochrane Database of Systematic Reviews, Cochrane CENTRAL Register of Controlled Trials, DARE, NHS-EED (NHS Economic Evaluation Database), HTA database, Science Citation Index, BIOSIS previews and the Current Controlled Trials research register were searched in June 2008. Data were extracted by one reviewer and checked by a second. REVIEW METHODS: The synthesis methods used were systematic review and meta-analysis for RCTs and qualitative framework synthesis for qualitative studies. A health economic model was developed to assess the cost-effectiveness of chemoprevention for two populations with different levels of risk of developing CRC: the general population and an intermediate-risk population. RESULTS: The search identified 44 relevant RCTs and six ongoing studies. A small study of aspirin in FAP patients produced no statistically significant reduction in polyp number but a possible reduction in polyp size. There was a statistically significant 21% reduction in risk of adenoma recurrence [relative risk (RR) 0.79, 95% confidence interval (CI) 0.68 to 0.92] in an analysis of aspirin versus no aspirin in individuals with a history of adenomas or CRC. In the general population, a significant 26% reduction in CRC incidence was demonstrated in studies with a 23-year follow-up (RR 0.74, 95% CI 0.57 to 0.97). Non-aspirin NSAID use in FAP individuals produced a non-statistically significant reduction in adenoma incidence after 4 years of treatment and follow-up and reductions in polyp number and size. In individuals with a history of adenomas there was a statistically significant 34% reduction in adenoma recurrence risk (RR 0.66, 95% CI 0.60 to 0.72) and a statistically significant 55% reduction in advanced adenoma incidence (RR 0.45, 95% CI 0.35 to 0.58). No studies assessed the effect of non-aspirin NSAIDs in the general population. There were no studies of folic acid in individuals with FAP or HNPCC. There was no significant effect of folic acid versus placebo on adenoma recurrence (RR 1.16, 95% CI 0.97 to 1.39) or advanced adenoma incidence in individuals with a history of adenomas. In the general population there was no significant effect of folic acid on risk of CRC (RR 1.13, 95% CI 0.77 to 1.64), although studies were of relatively short duration. Calcium use by FAP patients produced no significant reduction in polyp number or disease progression. In individuals with a history of adenomas there was a statistically significant 18% reduction in risk of adenoma recurrence (RR 0.82, 95% CI 0.69 to 0.98) and a non-significant reduction in risk of advanced adenomas (RR 0.77, 95% CI 0.50 to 1.17). In the general population there was no significant effect of calcium on risk of CRC (RR 1.08, 95% CI 0.87 to 1.34), although studies were of relatively short duration. There were no studies of antioxidant use in individuals with FAP or HNPCC, and in individuals with a history of adenomas no statistically significant differences in relative risk of adenoma recurrence were found. In the general population there was no difference in incidence of CRC (RR 1.00, 95% CI 0.88 to 1.13) with antioxidant use compared with no antioxidant use. Twenty studies reported qualitative findings concerning chemoprevention. People are more likely to use NSAIDs if there is a strong perceived need. Perceptions of risk and benefit also influence decision-making and use. People have fewer concerns about using antioxidants or other supplements, but their perception of the benefits of these agents is less well-defined. The model analysis suggested that the most cost-effective age-range policy in the general population would be to provide chemoprevention to all individuals within the general population from age 50 to 60 years. The use of aspirin in addition to screening within the general population is likely to result in a discounted cost per life-year gained of around 10,000 pounds and a discounted cost per quality-adjusted life-year (QALY) gained of around 23,000 pounds compared with screening alone. In the intermediate-risk group the most economically viable age-range policy would be to provide chemoprevention to individuals following polypectomy aged 61 to 70 years. Calcium is likely to have a discounted cost per QALY gained of around 8000 pounds compared with screening alone. Although aspirin in addition to screening should be more effective and less costly than screening alone, under the current assumptions of benefits to harms of aspirin and calcium, aspirin is expected to be extendedly dominated by calcium. LIMITATIONS: Whilst a number of studies were included in the review, the duration of follow-up was generally insufficient to detect an effect on cancer incidence. Given the uncertainties and ambiguities in the evidence base, the results of the health economic analysis should be interpreted with caution. CONCLUSIONS: Aspirin and celecoxib may reduce recurrence of adenomas and incidence of advanced adenomas in individuals with an increased risk of CRC and calcium may reduce recurrence of adenomas in this group. COX-2 inhibitors may decrease polyp number in patients with FAP. There is some evidence for aspirin reducing the incidence of CRC in the general population. Both aspirin and NSAIDs are associated with adverse effects so it will be important to consider the risk-benefit ratio before recommending these agents for chemoprevention. The economic analysis suggests that chemoprevention has the potential to represent a cost-effective intervention, particularly when targeted at intermediate-risk populations following polypectomy.