diagnosis of diabetes

Overview Content
UNDERSTANDING DIABETES
What's new in diabetes care Introduction to diabetes Types of diabetes Diagnosis Risk factors & screening
MANAGING DIABETES
Treatment Oral medications Insulin therapy Dietary therapy Physical exercise
MONITORING DIABETES
Glucose monitoring Self blood glucose monitoring
DIABETIC COMPLICATIONS
Acute complications Diabetic eye disease Neuropathy Diabetic foot problems Nephropathy Large vessel disease
DIABETES RELATED PROBLEMS
Diabetes and the skin Metabolic syndrome Depression and diabetes Diabetes in pregnancy

Diagnosis of Diabetes

How is diabetes diagnosed?
What is pre-diabetes and what is the significance?
Why is the control of postprandial blood glucose important?

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How is diabetes diagnosed?

The fasting blood glucose test is the preferred method to diagnose diabetes. Random blood glucose over 11.0 mmol/l (200mg/dl) is also diagnostic for diabetes mellitus when symptoms are present.

The diagnostic criteria for diabetes mellitus established by WHO has been revised by the American Diabetes Association through their Expert Committee on Diagnosis and Classification of Diabetes Mellitus in 1997. Recently, the upper limit of normal fasting blood glucose has further been lowered from 6.0 mmol/l (110 mg/dl) to 5.6 mmol/l (100 mg/dl).

Plasma glucose values for the diagnosis of diabetes mellitus and other categories of hyperglycaemia using fasting and 2-hour post glucose load (75g) samples are shown in the table below:

Diagnosis	Plasma glucose comcentration
Diabetes mellitus
Fasting and/or	7.0 mmol/l or more (126 mg/dl or more)
2-hour post glucose load (OGTT)	11.1 mmol/l or more (200 mg/dl or more)
Impaired glucose tolerance*
Fasting (if measured)	<7.0 mmol/l (<126 mg/dl)
2-hour post glucose load	7.8 - 11.0 mmol/l (140 - 200 mg/dl)
Impaired fasting glucose*
Fasting	5.6 - 6.9 mmol/l (100 - 125 mg/dl)
2-hour post glucose load (if measured)	<7.8 mmol/l (<140 mg/dl)
Normal
Fasting AND	<5.6 mmol/l (100 mg/dl)
2-hour post glucose load	<7.8 mmol/l (140 mg/dl)
* Pre-diabetes

OGTT (Oral glucose tolerance test) – a blood sample is taken after at least 8 hours overnight fast e.g. fasting blood glucose test. The test is repeated 2 hours after receiving 75 grams of glucose (100 grams for pregnant women).

What is pre-diabetes and what is the significance?

It is now accepted that impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are “pre-diabetic” states – blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes.

IGT is defined as a 2-hr blood glucose level of ≥7.8 mmol/l (140 mg/dl) but < 11.1 mmol/l (200 mg/dl) following a 75 g oral glucose tolerance test. People with IGT have one in three chance of developing Type 2 diabetes within 10 years. Recent research has shown that some long-term damage to the body, especially the heart and circulatory system, may already be occurring during pre-diabetes. Therefore IGT is associated with an increased risk of coronary artery disease and stroke.

IFG is defined as fasting blood glucose between 5.6 mmol/l (100mg/dl) and 6.9 mmol/l (125 mg/dl). It identifies risk of future diabetes.

Persons with combined IGT and IFG have a greater probability of progression to diabetes. Research has shown that if you take action to manage your blood glucose when you have pre-diabetes, you can delay or prevent type 2 diabetes from ever developing.

Why is the control of postprandial blood glucose important?

Postprandial hyperglycaemia is usually defined as blood glucose levels of ≥7.8 mmol/l (140 mg/dl) 2 hours after the start of a meal.

Studies have shown that diabetic patients who had raised glucose levels after meals, despite normal fasting glucose values, had increased incidence of microvascular complications including retinopathy. It is also an independent risk factor for macrovascular complications such as stroke and heart attack with increased risk of death, not only in patients with diabetes or those with IGT but also in normal individuals.

Therefore postprandial blood glucose levels should be monitored and adequately controlled, in addition to HbA1c and fasting blood glucose levels. Food with low glycemic index should be encouraged. Drugs that are able to reduce postprandial hyperglycemia include acarbose, repaglinide or nateglinide, short-acting insulin analogues e.g. insulin lispro, insulin aspart.

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