The bottom line

• People with glycated haemoglobin between 42 and 47 mmol/mol or fasting plasma glucose between 5.5 and 6.9 mmol/L are at high risk of diabetes
  

• Weight loss and lifestyle change can reduce this risk considerably

• Consider metformin or orlistat for prevention of diabetes in people at high risk, if intensive lifestyle intervention is not sufficient or suitable

A 45 year old white man comes to see you to discuss his blood glucose result. This was measured because he had an elevated QDiabetes risk score of 15%¹, as well as a brother with diabetes. His glycated haemoglobin (HbA_1c) is 43 mmol/mol (6.1%).

    What you should cover

    This man is at high risk of developing diabetes. Guidance from the UK National Institute for Health and Care Excellence (NICE) suggests that risk of diabetes should be determined by using a computer based risk assessment tool such as the QDiabetes risk calculator (http://qdiabetes.org/), Cambridge diabetes risk score, or Leicester practice score.2 If the risk assessment tool suggests elevated risk (for example >10% over 10 years), a fasting plasma glucose or HbA_1c test should be offered. Fasting plasma glucose of 5.5-6.9 mmol/L or HbA_1c between 42 and 47 mmol/mol indicates a high risk of diabetes (table1).

         Table1  Diagnostic criteria for diabetes and impaired glucose regulation

With the added information from your patient’s HbA_1c result, you now estimate that his risk of progressing to type 2 diabetes is around 5% per year^2，3. Importantly, intervention at this stage may reduce his risk.

• Consider whether the patient has any condition that may render HbA_1c inaccurate. Although NICE now recognises glycated haemoglobin as a valid screening test for type 2 diabetes in adults, certain medical conditions may falsely lower HbA_1c (for example, haemoglobinopathy, blood loss) or raise it (for example, iron deficiency anaemia, renal failure, HIV treatment, hypertriglyceridaemia, hyperbilirubinaemia).

• Check his blood pressure, weight, and body mass index.

• Discuss other risk factors for diabetes, such as drugs (for example, thiazide diuretics, β blockers, atypical antipsychotics, and steroids), comorbidities (for instance, cardiovascular disease or mental health problems), shift working, stress, and smoking.

• Ask what he understands about diabetes and its potential complications.

• Review his physical activity levels and dietary habits. In particular, ask about portion sizes and intake of fat, salt, sugar, and fruit and vegetables.

What you should do

• Check if the patient is taking any medication that may increase his risk of diabetes and, if so, consider alternatives.

• Advise that the screening test for diabetes shows that he does not have diabetes, but that if nothing changes in relation to his lifestyle he is at high risk of developing the condition. Explain that this risk may be greatly reduced by maintaining a healthy weight and being physically active; long term lifestyle change may be more effective than drugs in preventing or delaying type 2 diabetes.

•  Explain that diabetes is a lifelong condition, which may lead to important complications and reduce his quality and quantity of life. Make your patient aware that good control can reduce the risk of problems later on, particularly retinopathy, nephropathy, and neuropathy.

•  If he is overweight or obese, consider discussing other risks associated with overweight/obesity such as certain cancers, cardiovascular disease, arthritis, and sleep apnoea.

• Losing around 6-7% of one’s current body weight can lead to a 58% reduction in the risk of developing type 2 diabetes over three to five years^4，5. However, encourage him to set himself specific, realistic weight loss goals and to include friends and family in his plans.

• Encourage him to incorporate more physical activity into his daily routine, as even small increases in activity are beneficial². For example, using the stairs at work or getting off the bus one stop earlier.

• Advise him to reduce his intake of saturated fat and refined sugar. He could consider increasing his intake of wholegrains and vegetables.

• If he smokes, offer smoking cessation advice and support to reduce his risk of diabetes and cardiovascular disease.

• Refer your patient to a local intensive lifestyle change programme if this is available.

• Decide on a reasonable timescale in which to review your patient’s progress with his lifestyle goals. The HbA_1cshould be repeated at least annually from now on.

• NICE guidance suggests that if your patient continues to progress towards diabetes despite participation in an intensive lifestyle change programme, or is unable to participate owing to disability or medical problems, you should consider prescribing metformin, which is associated with a 20%-25% reduction in risk of developing diabetes over three to five years^4，5. Check renal function before starting; start at 500 mg once daily, and titrate up to 2000 mg daily if tolerated.

•  If you prescribe metformin, explain that it will be for 6-12 months initially. HbA_1c should be monitored regularly (every three months according to NICE) and metformin stopped if no benefit is seen. Check renal function at least twice a year while your patient is taking metformin.

•  Consider orlistat for prevention of diabetes in people with a body mass index of 28 or above who are unable to lose weight through lifestyle change alone. Review the use of orlistat after 12 weeks. If the patient has not lost at least 5% of his original body weight, use clinical judgment to decide whether to stop the orlistat. In severely obese patients, bariatric surgery can be considered, in line with NICE guidance.

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Tahseen Ahmad Chowdhury, consultant in diabetes and metabolism¹, 

Rupal Shah, general practitioner partner²

¹Department of Diabetes and Metabolism, The Royal London Hospital Whitechapel, London E1 1BB, UK

²Bridge Lane Group Practice, London SW11 3AD, UK

Correspondence to: R [email protected]

This is part of a series of occasional articles on common problems in primary care. The BMJ welcomes contributions from GPs.

Competing interests: We have read and understood the BMJ policy on declaration of interests and declare the following interests: none.

Provenance and peer review: Not commissioned; externally peer reviewed.

References

1. QDiabetes^® diabetes risk calculator. http://qdiabetes.org/.

2. National Institute for      Health and Care Excellence. Preventing type 2 diabetes: risk      identification and interventions for individuals at high risk. NICE, 2012.

3. Laaksonen DE, Lakka HM,      Niskanen LK, Kaplan GA, Salonen JT, Lakka TA. Metabolic syndrome and      development of diabetes mellitus: application and validation of recently      suggested definitions of the metabolic syndrome in a prospective cohort      study. Am J Epidemiol 2002;156:1070-7.

4. Knowler WC,      Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2      diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393-403.

5. Tuomilehto J, Lindstrom      J, Eriksson JG, et al. Prevention of type 2 diabetes mellitus by changes      in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 2001;344:1343-50.