General practice management of type 2 diabetes


Glycaemic monitoring
×
☰ Table of contents


Recommendations

Reference

Grade*

Glycated haemoglobin (HbA1c) measurement should be used to assess long-term blood glucose control

96
NHMRC, 2009

A

Self-monitoring of blood glucose is recommended for patients with type 2 diabetes who are using insulin where patients have been educated in appropriate alterations in insulin dose (Refer to Self-monitoring of blood glucose under Section 8.2. Medication for examples of instances when self-monitoring of blood glucose  may be considered)

65
SIGN, 2014

B

Routine self-monitoring of blood glucose in people with type 2 diabetes who are using oral glucose-lowering drugs (with the exception of sulphonylureas) is not recommended

65
SIGN, 2014

B

*Refer to Summary, explanation and source of recommendations for an explanation of the level of evidence and grade of evidence


Clinical context


Accuracy and limitations of the HbA1c test

Koenig first proposed the measurement of HbA1c in patients with diabetes as a marker for evaluating long-term control of diabetes in 1976.97 Over time, this has become a gold standard.

There are potential pitfalls of HbA1c as a measure of long-term diabetes management, and all diabetes clinicians should be aware of natural test variations and conditions that affect HbA1c results.

HbA1c measurement and natural test variation

HbA1c can be measured and reported using two different standards: the National Glycohemoglobin Standardization Program method reported as a per cent of units (eg 7%) and the newer International Federation of Clinical Chemistry standardisation reported as mmol/mol (eg 53 mmol/mol).

The variability of HbA1c values within Australia is now acceptably low. In a recent Australian study, more than 90% of HbA1c results fell within 6% of the median. A true level of 53 mmol/mol or 7.0% may be reported as anywhere between 49 mmol/mol or 6.6% and 57 mmol/mol or 7.4%.38

This variation needs to be considered when monitoring long-term glucose control.

Conditions affecting the HbA1c result

Any condition that shortens erythrocyte survival or decreases mean erythrocyte age will falsely lower HbA1c test results regardless of the assay method used (Table 4).

The presence of abnormal haemoglobin variants can cause unusually high HbA1c (eg HbF, HbE, HbD, HbJ Capetown, Hb Raleigh) or unusually low HbA1c readings (eg HbS, HbC, HbJ, HbG, Hb Ramadan).
 

Table 4. Other causes of variances to HbA1c

Abnormally low glycated haemoglobin (HbA1c)

  • Haemolytic anaemia: congenital (eg spherocytosis, elliptocytosis), haemoglobinopathies, acquired haemolytic anaemias (eg drug-induced such as with dapsone, methyldopa)
  • Recovery from acute blood loss
  • Chronic blood loss
  • Chronic renal failure (variable)

Abnormally high HbA1c

  • Iron deficiency anaemia98
  • Splenectomy
  • Alcoholism
  • Steroid therapy, stress, surgery or illness in the past three months

 

Several situations may indicate the presence of a haemoglobinopathy, including when:

  • results of SMBG have a low correlation with HbA1c results
  • an HbA1c result is discordant with measured laboratory glycaemia
  • an HbA1c result is more than 15%
  • a patient’s HbA1c test result is radically different from a previous test result following a change in laboratory HbA1c measurement methods.

If a haemoglobinopathy is suspected, then a haemoglobin electrophoresis is suggested. Schnedl et al reported a prevalence of abnormal haemoglobin variants of 0.6% among 15,000 HbA1c estimations in a period of over six years.99

Reliable HbA1c tests, in which haemoglobin variants do not cause interference, are available. Otherwise, alternative forms of diabetes monitoring such as continual blood glucose estimations, SMBG and fructosamine should be considered for these patients.

Self-monitoring of blood glucose

Self-monitoring in patients with type 2 diabetes is usually recommended:

  • for patients on insulin and glucose lowering agents that can cause hypoglycaemia
  • when monitoring hyperglycaemia arising from illness (Chapter 11. Glycaemic emergencies and Appendix J. Detailed information on glycaemic emergencies)
  • with pregnancy and pre-pregnancy planning
  • when changes in treatment, lifestyle or other conditions requires data on glycaemic patterns
  • when HbA1c estimations are unreliable (eg haemoglobinopathies).

The method and frequency of monitoring need to reflect individual circumstances and therapeutic aims, and where the person with diabetes and their healthcare providers have the knowledge, skills and willingness to incorporate SMBG and therapy adjustments into diabetes care plans.

A 2012 Cochrane review on the effect of SMBG in patients with type 2 diabetes not using insulin found limited clinical benefit as measured by HbA1c from SMBG. Therefore, routine SMBG for people with type 2 diabetes who are considered low risk and using oral glucose lowering drugs (with the exception of sulphonylureas) is not recommended.100–104

 

In practice


Recommendations

Reference

Grade*

Blood glucose control should be optimised because of its beneficial effects on the development and progression of microvascular complications

96
NHMRC, 2009

A

The potential harmful effects of optimising blood glucose control in people with type 2 diabetes should be considered when setting individual glycaemic targets

 

A

The general glycated haemoglobin (HbA1c) target in people with type 2 diabetes is ≤53 mmol/mol (≤7%). Adjustments to diabetes
treatment should be considered when HbA1c is above this level

96
NHMRC, 2009

A

Targets for self-monitoring of blood glucose levels are 6–8 mmol/L for fasting and preprandial, and 6–10 mmol/L for two hour postprandial

96
NHMRC, 2009

C

*Refer to Summary, explanation and source of recommendations for an explanation of the level of evidence and grade of evidence


HbA1c targets and individualisation

The general HbA1c target in people with type 2 diabetes is HbA1c ≤53 mmol/mol (≤7%). Due to the natural variation of HbA1c test results, a target HbA1c of 53 mmol/mol would be achieved by laboratory results being in a range of 48–58 mmol/mol (6.5–7.5%).

All patients with diabetes need to optimise their blood glucose control to improve short-term and long-term health outcomes. However, what is ‘optimal’ will vary depending on the balance between benefits and risks, and the patient’s priorities (Figure 3).

Given the range of diabetes presentations to general practice, there is no single glycaemic target that suits all patients. Targets need be individualised and balanced against patient capabilities and the risk of severe hypoglycaemia, especially among older people.

Control of diabetes symptoms (eg polydipsia, polyuria) can usually be achieved around a HbA1c level of 64 mmol/mol (8%). This does not necessarily mean optimum metabolic control.

More stringent HbA1c targets might be considered in selected patients (eg those with short disease duration, long life expectancy, no significant CVD) if this can be easily and safely achieved without significant hypoglycaemia or other adverse effects of treatment. 
 

Figure 3. Approach to management of hyperglycaemia

Figure 3. Approach to management of hyperglycaemia


Not everyone benefits from long-term intensive glucose management.

Less stringent HbA1c goals (eg 58–64 mmol/mol [7.5–8.0%] or even slightly higher) are appropriate for patients with a history of severe hypoglycaemia, limited life expectancy, advanced complications, extensive comorbid conditions, and those for whom the target is difficult to attain despite intensive self-management education, repeated counselling, and effective doses of multiple glucose-lowering agents, including insulin.105

Targets for self-monitored glycaemic control in type 2 diabetes are shown in Table 5.

Table 5. Targets for self-monitored glycaemic control in type 2 diabetes

Fasting blood glucose (FBG; mmol/L)

Preprandial blood glucose (mmol/L)

Postprandial blood glucose (mmol/L)

Comment

6.0–8.0

6.0–8.0

6.0–10.0

NHMRC values96


Diabetes Australian and RACGP logo's
 
  1. Colagiuri S, Dickinson S, Girgis S, Colagiuri R. National evidence based guideline for blood glucose control in type 2 diabetes. Canberra: NHMRC, 2009.
  2. Sundaram RC, Selvaraj N, Vijayan G, Bobby Z, Hamide A, Rattina Dasse N. Increased plasma malondialdehyde and fructosamine in iron deficiency anemia: Effect of treatment. Biomed Pharmacother 2007;61(10):682–85.
  3. Bosi E, Scavini M, Ceriello A, et al. Intensive structured self-monitoring of blood glucose and glycemic control in noninsulin-treated type 2 diabetes: the PRISMA randomized trial. Diabetes Care 2013;36(10):2887–94.
  4. Farmer AJ, Perera R, Ward A, et al. Meta-analysis of individual patient data in randomised trials of self monitoring of blood glucose in people with non-insulin treated type 2 diabetes. BMJ 2012;344:e486.
  5. Malanda UL, Welschen LM, Riphagen II, Dekker JM, Nijpels G, Bot SD. Self-monitoring of blood glucose in patients with type 2 diabetes mellitus who are not using insulin. Cochrane Database Syst Rev 2012;1:CD005060.
  6. Nauck MA, Haastert B, Trautner C, Muller UA, Nauck MA, Heinemann L. A randomised, controlled trial of self-monitoring of blood glucose in patients with type 2 diabetes receiving conventional insulin treatment. Diabetologia 2014;57(5):868–77.
  7. Schnell O, Barnard K, Bergenstal R, et al. Clinical utility of SMBG: Recommendations on the use and reporting of SMBG in clinical research. Diabetes Care 2015;38(9):1627–33.
  8. Inzucchi SE, Bergenstal RM, Buse JB, et al. Management of hyperglycemia in type 2 diabetes, 2015: A patient-centered approach: Update to a position statement of the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care 2015;38(1):140–49.