Guideline update – preventing diabetes

The guideline: NICE Risk identification and interventions to prevent type 2 diabetes in adults at high risk: summary of NICE guidance PHG38. NICE August 2012.

Almost three million people in the UK have diabetes, and about 850,000 are undiagnosed. It is thought that many people with type 2 diabetes may have had the condition for nine to 12 years before diagnosis and many will already have macrovascular and microvascular complications.¹

About 15% of adults have impaired glucose regulation – pre-diabetes – and an estimated 5–12% of them will develop type 2 diabetes each year.² Increasing evidence that treating pre-diabetes early and aggressively can dramatically reduce the risk of developing the disease led NICE to develop this guideline.³

The latest such evidence – published in The Lancet in June – compared lifestyle intervention, metformin or placebo in 1,990 patients with impaired glucose tolerance. Six years later those patients whose blood glucose levels had dropped to normal when tested at least three times in that period were up to 70% less likely to have diabetes than those on placebo, regardless of how that drop was achieved.⁴

This article summarises the recommendations from the NICE guidance which are of particular interest to GPs. But it also identifies the barriers to its implementation, which are significant.

Identifying high-risk patients

The guidance recommends a two-stage approach to those at highest risk of developing diabetes – the first based on risk factors and the second using HbA₁c measurement, or a fasting blood glucose.

Stage 1

• GP practices should use a validated, computer-based risk-assessment tool to search their register for those at higher risk of type 2 diabetes between the ages of 40 and 69.
• These tools will also identify younger patients with risk factors such as ethnicity (South Asian, African-Caribbean, Chinese, or black African descent), being overweight or obese, or having a first-degree relative with type 2 diabetes. Three such tools are mentioned in the guidance:

- the Cambridge diabetes risk score

- Leicester practice risk score

- QDiabetes.

• Opportunistic screening can be carried out in other settings – either using one of these tools or a validated patient questionnaire such as the Diabetes Risk Score assessment tool provided by Diabetes UK which can be accessed at pulsetoday.co.uk/tools-and-resources.

Anyone who is identified as being at higher risk should be advised to see their GP for a blood test.

Stage 2

• Those identified as having a higher risk score should be invited to the surgery to have their HbA₁c or fasting plasma glucose (FPG) checked, although it’s likely HbA₁c will be the preferred choice so those values will be used here. Equivalent values for FPG testing are available in the guidance.
• Those HbA₁c levels should then be used to reclassify these patients into three groups.

Classifying according to risk

Moderate risk

• Patients with a HbA₁c of less than 42mmol/mol (6%) are classified as moderate risk.
• This group should be offered what NICE terms a brief intervention – a GP or practice nurse consultation to discuss the risks of developing diabetes and give advice on modifying risk. Support services such as weight-loss programmes should be offered.
• Their risk should be reassessed at least every three years.

High risk

• Those with a HbA₁c of between 42 and 47mmol/mol (6-6.4%) are classified as high risk.
• They should be referred to an ‘intensive lifestyle change programme’ – exercise, weight loss and changes to their diet.
• Their progress should be monitored at least annually by checking HbA₁c or FPG and BMI.

Possible type 2 diabetes

• Anyone with a HbA₁c of 48mmol/mol (6.5%) or over should be further investigated for type 2 diabetes with either a second HbA₁c, a fasting blood glucose or an oral glucose tolerance test.
• If a diagnosis is not confirmed, these patients should be managed as high risk.

Referring for intensive lifestyle programmes

• This is one of the most ambitious parts of the guidance, as the criteria for such programmes are strictly defined and currently beyond the scope of most practices.
• An intensive lifestyle programme should be offered to those at high risk to:

– undertake a minimum of 150 minutes of moderate-intensity physical activity a week

– reach and maintain a healthy BMI

– Increase consumption of wholegrains, vegetables, and other foods high in dietary fibre

– reduce the total amount of fat in their diet

– eat less saturated fat.

• These programmes can be delivered to groups of 10–15 people meeting at least eight times over nine to 18 months.
• Participants should have at least 16 hours of contact time within a group, either on a one-to-one basis or sometimes as a group.
• Follow-up sessions should be offered at regular intervals (for example, every three months) for at least two years after the initial intervention period.
• Those with a BMI of 30 or more (27.5 or more if South Asian or Chinese) should be offered a structured weight-loss programme.

Metformin for those who do not respond to lifestyle change

• NICE has recommended standard-release metformin should be offered to people whose HbA₁c or FPG has not improved if:

– this has happened despite their participation in an intensive lifestyle-change programme, or

– they are unable to participate in an intensive lifestyle-change programme.

• Advice on diet and physical activity plus support to achieve goals should continue.
• Start with a low dose (500mg once daily) and then increase gradually as tolerated, to a maximum 2,000mg daily.
• If the patient is intolerant of standard metformin, consider using a modified-release formulation.
• Prescribe metformin for six to 12 months initially. Monitor FPG or HbA₁c at three-month intervals and stop if no effect is seen.
• Although the guidance makes no reference to it, this is not a licensed indication and GPs are simply advised to ‘discuss with the person the potential benefits and limitations of taking metformin’ – and of course we should record this in the notes.

The role of orlistat

• Orlistat should be considered in patients with a BMI of 28 or more as part of an overall plan for managing obesity.
• Review after 12 weeks and, if the patient has not lost at least 5% body weight, consider stopping.
• Remember adults with type 2 diabetes lose weight more slowly, and the same may be true of those with pre-diabetes.

Barriers to implementation

As stated earlier, this is a hugely ambitious public health programme that will need considerable service design and funding to be effective. Some concerns are:

• The lifestyle interventions recommended are not of the level currently offered by many practices – although NICE does include primary healthcare teams as a group that should be developing these services. Without significant funding this seems unlikely and the hope is these services will develop in the same way that NICE’s recommendations on CBT led to the IAPT program.
• Diabetes risk assessment is already part of the NHS health check programme – as the guidance states – it will take ‘clear and timely communication’ to co-ordinate risk identification across different settings.
• The use of metformin outlined here is unlicensed and widespread, and so must be addressed by the regulatory authorities.
• There are significant gaps in the evidence including:

– limited evidence on how diabetes prevention trials translate into UK practice.

– how incentives – to either patient or provider – could increase effectiveness

– whether a risk-assessment tool alone and/or a FPG or HbA₁c is more effective in detecting prediabetes.