☰ Table of contents
Clinical suspicion for type 2 diabetes needs to remain high, as type 2 diabetes is often asymptomatic and developing in younger populations. Secondary causes of diabetes should also be considered in the presence of symptoms suggestive of diabetes.31
Clinical signs of insulin resistance
Signs of insulin resistance may include the following:
- Acanthosis nigricans (AN) – Typically characterised by hyperpigmentation (darkening of skin pigment) and usually accompanied by a velvety change in texture of the affected skin. Common sites are the neck and axillae.32
- Skin tags – Benign (non-cancerous) skin growths on the body or face. They can be smooth or wrinkled, skin-coloured or just slightly darker than skin colour and can vary in size.
- Central obesity – Defined by a high waist-to-hip ratio, waist-to-thigh ratio and waist circumference.
- Hirsutism – Excess facial and body hair, especially on women, which can indicate insulin resistance.
Box 2 provides examples clarifying when insulin levels may be useful.
Box 2. When are insulin levels helpful?
- There is no role for routinely testing insulin levels to assess insulin resistance in impaired glucose tolerance (IGT), impaired fasting glucose (IFG) or in the evaluation of type 2 diabetes/li>
- Patients with signs of insulin resistance should be screened for diabetes with fasting blood glucose (FBG) or glycated haemoglobin (HbA1c)
Diagnosis of diabetes in asymptomatic patients
Testing those at high-risk or with a clinical suspicion for diabetes involves three types of biochemical analyses (Box 3).
Box 3. Diagnostic criteria for type 2 diabetes
- Fasting blood glucose (FBG) ≥7.0 mmol/L or random blood glucose ≥11.1 mmol/L confirmed by a second abnormal FBG on a separate day
- Oral glucose tolerance test (OGTT) before (fasting) and two hours after an oral 75 g glucose load is taken. Blood glucose is measured.
Glycated haemoglobin (HbA1c) ≥48 mmol/mol (6.5%; on two separate occasions)
- Diabetes is diagnosed as FBG ≥7.0 mmol/L or two-hour blood glucose is ≥11.1 mmol/L
These are via venous sampling under laboratory methodology
Confirmatory testing for asymptomatic patients
A second laboratory result is required for confirmation of the diagnosis of diabetes in asymptomatic patients. It is recommended that the same laboratory result be repeated without delay using a new blood sample for confirmation because there will be a greater likelihood of concurrence.
Figure 1a. Screening and diagnosis algorithm – Fasting blood glucose
Figure 1b. Screening and diagnosis algorithm – Glycated haemoglobin
Figure 1c. Screening and diagnosis algorithm – Oral glucose tolerance test
Practice Points for diagnosed diabetes
Monitor risk factors, and symptoms:
- Manage the individual patient by assessing modifiable risk factors and CVD risk
- Refer patients to a dietitian and a physical activity program
- P rovide pre-conception advice to women in reproductive age with a history of gestational diabetes
‡Provide access to diabetes health teams, and commence lifestyle modifications and/or medication. Register with the NDSS and notify the RTA
§ Medicare Benefits Schedule (MBS) item number 66841 allows for diagnostic use only once every 12 months. The request slip should be annotated as HbA1c for Service Incentive Payment (SIP) and Practice Incentives Program (PIP) purposes. However, a confirmatory HbA1c test (MBS item number 66551) should be ordered before treatment initiation37
|| A value of <48 mmol/mol (6.5%) does not exclude diabetes diagnosed using plasma glucose testing in symptomatic patients
NB: IGT and IFG cannot be diagnosed using HbA1c
Clinical symptoms suggestive of diabetes
Symptoms of diabetes include:
- lethargy, polyuria, polydipsia
- frequent fungal or bacterial infections
- blurred vision
- loss of sensation (ie touch, vibration, cold)
- poor wound healing
- weight loss.
Tests to detect diabetes in symptomatic patients
In the presence of symptoms suggestive of hyperglycaemia or a clear clinical diagnosis (eg a patient presenting with hyperglycaemic crisis, a single elevated FBG ≥7.0 mmol/L or a random blood glucose ≥11.1 mmol/L), this is confirmatory of a diagnosis of diabetes. A second laboratory test is not required to confirm the diagnosis.