Diagnostic background
The purpose of diagnosis is to identify those at risk of developing the complications of diabetes,
both arterial ( macrovascular ) and microvascular, as well as to deal with any symptoms
The levels of blood glucose vary for these different risks, and determine management
1. | Symptomatic ( biochemically confirmed ) | = | "Diabetes" |
2. | At risk of arterial and microvascular damage | = | "Diabetes" |
3. | At risk of arterial damage from hyperglycaemia | = | "Impaired Glucose Tolerance ( IGT )" |
and of progression to diabetes | or "Impaired Fasting Glycaemia ( IFG )" |
Plasma glucose* | Whole blood glucose | ||||||||
Venous* | Capillary | Venous | Capillary | ||||||
mmol/l | mg/dl | mmol/l | mg/dl | mmol/l | mg/dl | mmol/l | mg/dl | ||
Fasting | |||||||||
"Diabetes" | >=7.0 | >125 | >=7.0 | >125 | >6.0 | >=110 | >6.0 | >=110 | |
"IFG" | >6.0 | >=110 | >6.0 | >=110 | >5.5 | >=100 | >5.5 | >=100 | |
OGTT 2-h | |||||||||
"Diabetes" | >11.0 | >=200 | >=12.2 | >=220 | >=10.0 | >=180 | >11.0 | >=200 | |
"IGT" | >=7.8 | >=140 | >=8.9 | >=160 | >=6.7 | >=120 | >=7.8 | >=140 |
* preferred measure
OGTT: 75 g glucose in 300 ml water over 3-5 min
1. Fasting glucose estimations require a certainty of no previous calorie intake
2. Venous plasma glucose estimation is preferred
3. HbA1c ( glycated haemoglobin ) can be useful in clinical diagnosis
4. Diagnostic procedures should not be performed :
5. Diagnostic tests should be interpreted with reservation :
6. If suspicion or high risk of diabetes, but fasting glucose normal, do OGTT, particularly in the elderly
7. The above procedures are not applicable to people with hepatic cirrhosis or other extreme forms of peripheral insulin resistance