Preventing type 2 diabetes: risk identification and interventions for individuals at high risk
This is an extract from the guidance. The complete guidance is available at guidance.nice.org.uk/ph38
Appendix B Summary of the methods used to develop this guidance
- Introduction
- Guidance development
- Key questions
- Reviewing the evidence
- Commissioned report
- Cost effectiveness
- Fieldwork
- How the PDG formulated the recommendations
Introduction
The reviews, primary research, commissioned reports and economic modelling report include full details of the methods used to select the evidence (including search strategies), assess its quality and summarise it.
The minutes of the Programme Development Group (PDG) meetings provide further detail about the Group's interpretation of the evidence and development of the recommendations.
All supporting documents are listed in appendix E and are available at the NICE website.
Guidance development
The stages involved in developing public health programme guidance are outlined in the list below.
1. Draft scope released for consultation
2. Stakeholder meeting about the draft scope
3. Stakeholder comments used to revise the scope
4. Final scope and responses to comments published on website
5. Evidence reviews and economic modelling undertaken and submitted to PDG
6. PDG produces draft recommendations
7. Draft guidance (and evidence) released for consultation and for field testing
8. PDG amends recommendations
9. Final guidance published on website
10. Responses to comments published on website
Key questions
The key questions were established as part of the scope. They formed the starting point for the reviews of evidence and were used by the PDG to help develop the recommendations. The overarching questions were:
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What are the most effective and cost-effective methods of identifying and monitoring adults with either or both impaired fasting glucose (IFG) and impaired glucose tolerance (IGT)?
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What are the most effective and cost-effective methods – lifestyle, pharmacological and surgical – of preventing or delaying type 2 diabetes in adults with pre-diabetes?
The subsidiary questions were:
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How does effectiveness and cost effectiveness vary between different communities or groups, including disadvantaged groups?
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Which interventions or strategies, and which combinations of interventions or strategies, are the most effective and cost effective in preventing or delaying type 2 diabetes in adults with pre-diabetes within a given community?
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What are the barriers and facilitators that may affect the implementation, effectiveness and cost effectiveness of these interventions or strategies (this should include any barriers and facilitators for specific groups)?
These questions were made more specific for each review (see reviews for further details).
Reviewing the evidence
Evidence reviews
Three reviews of effectiveness were conducted (reviews 1 to 3) and one qualitative review (review 4).
Identifying the evidence
A number of databases were searched in September 2010 for experimental studies, surveys and qualitative studies (1990–2010). See each review for details of the databases searched.
The grey literature was searched via: British Library Integrated Catalogue, Conference Papers Index, Medical Research Council and Economic and Social Research Council.
Searches of a range of websites were carried out for individual reviews (the sites searched varied between reviews – see each review for details).
Selection criteria
Studies were included in the three effectiveness reviews if:
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Review 1: they involved the identification and risk assessment of adults with IFG/IGT or raised glycated haemoglobin (HbA1c).
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Review 2: they were randomised controlled trials that:
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included people with pre-diabetes
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investigated lifestyle, drug and surgical interventions to prevent type 2 diabetes
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reported progression to type 2 diabetes as an outcome.
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Review 3: they included adults diagnosed with pre-diabetes using World Health Organization criteria (World Health Organization 2006) and evaluated interventions focused on:
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weight-loss (for example, education, motivational support, slimming clubs)
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diet (for example, low glycaemic index, reduced fat, controlled carbohydrate, low calorie diets)
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physical activity (for example, cardiorespiratory training, organised programmes, individual programmes).
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Studies were excluded from all three reviews if they focused on:
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people under 18 years of age
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people diagnosed with any form of diabetes
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pregnant women.
Studies were included in review 4 if they reported on views and perceptions of the following interventions delivered in primary, secondary and tertiary care, the community, residential care sector and prisons:
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Identification and risk assessment of adults with IFG/IGT or raised glycated haemoglobin (HbA1c).
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Implementation of lifestyle interventions to prevent progression to type 2 diabetes.
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Undertaking behaviour change as a diabetes prevention strategy.
Studies were excluded if they focused on people with any form of diabetes.
Quality appraisal
Included papers were assessed for methodological rigour and quality using the NICE methodology checklist, as set out in the NICE technical manual 'Methods for the development of NICE public health guidance' (see appendix E). Each study was graded (++, +, –) to reflect the risk of potential bias arising from its design and execution.
Study quality
++ All or most of the checklist criteria have been fulfilled. Where they have not been fulfilled, the conclusions are very unlikely to alter.
+ Some of the checklist criteria have been fulfilled. Those criteria that have not been fulfilled or not adequately described are unlikely to alter the conclusions.
– Few or no checklist criteria have been fulfilled. The conclusions of the study are likely or very likely to alter.
The evidence was also assessed for its applicability to the areas (populations, settings, interventions) covered by the scope of the guidance. Each evidence statement concludes with a statement of applicability (directly applicable, partially applicable, not applicable).
Summarising the evidence and making evidence statements
The review data was summarised in evidence tables (see full reviews).
The findings from the reviews were synthesised and used as the basis for a number of evidence statements relating to each key question. The evidence statements were prepared by the public health collaborating centre (see appendix A). The statements reflect the centre's judgement of the strength (quality, quantity and consistency) of evidence and its applicability to the populations and settings in the scope.
Commissioned report
The commissioned report focused on vulnerable groups whose risk of diabetes may be missed or difficult to manage. They included:
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frail older people
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adults with a physical disability, severe mental illness or learning disabilities
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those not registered with a GP
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prisoners
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travellers, refugees, asylum seekers and recent migrants
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homeless people
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some minority ethnic or cultural groups and some faith communities
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those living in poverty.
Cost effectiveness
There was a review of economic evaluations, including an economic modelling exercise.
Review of economic evaluations
The economic review focused on models and reviews published since 2005 which have addressed three key questions:
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What is the likely cost-effectiveness of interventions to identify and manage pre-diabetes?
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What are the main factors which will influence the cost-effectiveness of risk assessment and intervention in pre-diabetes?
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Is it more cost-effective to identify and actively intervene in risk assessment-detected pre-diabetes or risk assessment-detected diabetes, or both, given that any risk assessment programme will identify both?
Four cost-effectiveness models published in the last 3 years met the inclusion criteria. They made a wide range of assumptions about baseline risk and relevant costs. Nevertheless, cost-effectiveness studies and systematic literature reviews reported that risk assessment (combined with a diabetes test) for people at high risk is likely to be cost effective – at £10,000 per quality-adjusted life year (QALY) or less.
Economic modelling
A two-stage economic model was constructed to include (hypothetically) everyone from 40 to 74 years of age and people of South Asian, Chinese or African/African-Caribbean ethnicity aged 25 to 39. The NHS Health Check programme was used as the comparator. Discount rates of 3.5% for both costs and benefits, a lifetime time-horizon and an NHS perspective, were used.
The first stage divided the population by a risk score (practice-based or self-assessed). In the model, at the second stage those at high risk of progressing to diabetes in the following 10 years were offered an HbA1c or an FPG test. Those at high risk, based on the blood test, were offered an intensive lifestyle-change intervention.
The difference, in terms of costs and health benefits for both groups, as well as future costs saved by those assigned an intervention, were estimated. A cost per quality-adjusted life year (QALY) of less than £20,000 for the intervention was calculated, using data from the reviews of effectiveness and cost effectiveness.
For people of South Asian descent aged 25–39 years, the intervention improved their health and was estimated to be cost saving, compared with normal practice. The results are reported in: 'Prevention of type 2 diabetes: economic review and modelling' available on NICE's website.
Fieldwork
Fieldwork was carried out to evaluate how relevant and useful NICE's recommendations are for practitioners and how feasible it would be to put them into practice. It was conducted with:
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Practitioners delivering the NHS Health Check programme.
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GPs, dietitians, practice nurses, dentists, community pharmacists, public health and obesity specialists.
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Members of shadow health and wellbeing boards and other commissioning groups involved in primary and community-based healthcare services for people at risk of diabetes. This included those working in ophthalmology, diabetology and other secondary healthcare care services in the NHS.
The fieldwork comprised:
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Three discussion groups carried out in Birmingham, London and Manchester by Word of Mouth.
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Thirty telephone interviews carried out by Word of Mouth with some of those who were unable to attend a discussion group.
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An online consultation carried out by Word of Mouth with people who were not selected for the interviews, and were not able to attend a discussion group.
The three studies were commissioned to ensure there was ample geographical coverage. The main issues arising from these studies are set out in appendix C under fieldwork findings. See also the full fieldwork report 'Prevention of type 2 diabetes: risk identification and interventions for individuals at high risk'.
How the PDG formulated the recommendations
At its meetings from October 2010 to September 2011, the Programme Development Group (PDG) considered the evidence, expert reports and cost effectiveness to determine:
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whether there was sufficient evidence (in terms of strength and applicability) to form a judgement
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where relevant, whether (on balance) the evidence demonstrates that the intervention or programme/activity can be effective or is inconclusive
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where relevant, the typical size of effect (where there is one)
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whether the evidence is applicable to the target groups and context covered by the guidance.
The PDG developed draft recommendations through informal consensus, based on the following criteria:
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Strength (type, quality, quantity and consistency) of the evidence.
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The applicability of the evidence to the populations/settings referred to in the scope.
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Effect size and potential impact on the target population's health.
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Impact on inequalities in health between different groups of the population.
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Equality and diversity legislation.
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Ethical issues and social value judgements.
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Cost effectiveness (for the NHS and other public sector organisations).
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Balance of harms and benefits.
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Ease of implementation and any anticipated changes in practice.
The PDG noted that effectiveness can vary according to the context. For example interventions carried out as part of a major research study such as the Diabetes Prevention Programme produced greater changes in behaviour and modifiable risk factors than intervention carried out in real life settings.
Where possible, recommendations were linked to evidence statements (see appendix C for details). Where a recommendation was inferred from the evidence, this was indicated by the reference 'IDE' (inference derived from the evidence).
The draft guidance, including the recommendations, was released for consultation in June 2012. At its meeting in February 2012 the PDG amended the guidance in light of comments from stakeholders and experts and the fieldwork. The guidance was signed off by the NICE Guidance Executive in May 2012.