Journals club - Type-2 diabetes mellitus and HbA1c levels

Curriculum statement 15.6 metabolic problems

Key trials

  • There is a near linear relationship between glycaemic control and cardiovascular disease in people with type-2 diabetes (Diabet Med 2008; 25: 1295-301).
  • The ACCORD trial showed a significantly higher mortality rate in those patients who had been intensively treated to achieve glycaemic control compared with those who had received standard treatment (N Engl J Med 2008; 358: 2545-59).
  • The ADVANCE trial did not demonstrate an effect of intensive glycaemic control on the occurrence of major cardiovascular events or all-cause mortality (N Engl J Med 2008; 358: 2560-72).
  • The VADT trial found that intensive glucose control in patients with poorly controlled type-2 diabetes had no significant effect on cardiovascular events or death (N Engl J Med 2009; 360: 129-39).
  • Another trial has suggested that effects on mortality of intensive glucose control in newly diagnosed type-2 diabetes were sustained for up to 10 years (N Engl J Med 2008; 359: 1577-89).

Evidence base

  • A recent prospective cohort study showed that there is not much difference in mortality risk, as long as HbA1c levels are less than 9 per cent (Br J Gen Pract 2010; 60: 172-5).
  • A recent study using data from the UK General Practice Research Database found that, among people whose treatment had been intensified by the addition of insulin or a sulfonylurea, there was no benefit in reducing HbA1c below 7.5 per cent (Lancet 2010; 375: 481-9).

Guidelines

  • For patients with moderate glycaemic control and longstanding diabetes, it may be better to focus on other risk factors (such as smoking, hypertension, hyperlipidaemia) than to aim for increasingly lower HbA1c levels.
  • NICE recommends an HbA1c of 6.5 per cent for people with type-2 diabetes.
  • The American Diabetes Association advises that this should be 7 per cent, but that targets should be tailored to individual circumstances.
  • In April 2009, the QOF target for HbA1c was reduced from 7.5 per cent to 7 per cent in patients with type-2 diabetes. However, it has been suggested that this change of target should be withdrawn before it wastes resources and possibly harms patients (BMJ 2009; 338: b800).

Key points

  • There may be risks in lowering HbA1c too much in patients with diabetes.
  • Other risk factors, such as BP and lipid levels, may be more important than HbA1c levels.
  • Many experts feel that the current QOF target of 7 per cent is too low.
  • Many patients find it very challenging to lower HbA1c levels.

Contributed by Dr Louise Newson, a GP in the West Midlands

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