Diagnosis of Hyperglycaemic States

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

Management classification - hyperglycaemic states

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	"Impaired Fasting Glycaemia ( IFG )"

Diagnostic algorithm

1. Symptomatic or glycosuria or incidental hyperglycaemia

Check random venous plasma glucose ( see below for capillary / venous equivalents)

If >11.0 mmol/1 (>=200 mg/dl)

"Diabetes"

If >5.5 mmol/l (>=100 mg/dl ) then proceed to next step (2.)
(and review cause of symptoms)

2. Random or fasting screening glucose >5.5 mmol/l (>=100 mg/dl)

Check fasting venous plasma glucose

If >=7.0 mmol/1 (>125 mg/dI), repeat and if confirmed

"Diabetes"

If >6.0 mmol/l (>=1 10 mg/dl ) do oral glucose tolerance test ( OGTT)

If >5.0 mmol/l (>90 mg/dl), consider yearly reassessment of arterial risk factors, including plasma glucose

OGTT (venous plasma glucose):

If 2-h >11.0 mmol/l (>=200 mg/dl)

"Diabetes"

If 2-h <=11.0 mmol/l (<200 mg/dl ) and >=7.8 mmol/l (>=140 mg/dl)

"IGT"

If fasting >6.0 mmol/l (>=1 10 mg/dl ) and 2-h <7.8 mmol/l (<140 mg/dl)

"IFG"

See cautions in box below

Diagnostic equivalents for plasma and blood

Plasma glucose*

Whole blood glucose

Venous*
mmol/l mg/dl

Capillary
mmol/l mg/dl

Venous
mmol/l mg/dl

Capillary
mmol/l mg/dl

Fasting

"Diabetes"

>=7.0 >125

>6.0 >=110

"IFG"

>6 >=110

>6.0 >=110

>5.5 >=100

OGTT 2-h

"Diabetes"

>11.0 >=200

>=12.2 >=220

>=10.0 >=180

>=11.0 >=200

"IFG"

>=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

Diagnostic aids and caution

Fasting glucose estimations require a certainty of no previous calorie intake

	be suspicious if HbA_1c not consistently elevated
	if suspicious repeat after 2-h supervision, or consider OGTT
	diagnosis cannot be based on a single abnormal glucose estimation in the absence of symptoms

Venous plasma glucose estimation is preferred

	for convenience, equivalents for whole blood and capillary glucose estimations are given on previous page

HbA_1c ( glycated haemoglobin ) can be useful in clinical diagnosis

provided that confirmatory venous plasma glucose estimations are obtained

provided the assay is DCCT standardized, an HPLC chromatogram is reviewed for presence of abnormal haemoglobins, and erythrocyte turnover is not abnormal

approximately, HbA_1c

>7.5 % ~ fasting plasma glucose �7.0 mmol/l ( >125 mg/dl )

>6.5 % ~ fasting plasma glucose >6.0 mmol/l ( >=110 mg/dl )

Diagnostic procedures should not be performed :

	in the presence of acute illness or after trauma or surgery
	during short courses of blood glucose raising drugs

Diagnostic tests should be interpreted with reservation :

	in people on long-term blood glucose raising drugs
	in people with reversible endocrine conditions
	in pregnant women ( see also: Pregnancy in women with Type 2 diabetes )

6.	If suspicion or high risk of diabetes, but fasting glucose normal, do OGTT, particularly in the elderly

The above procedures are not applicable to people with hepatic cirrhosis or other extreme forms of peripheral insulin resistance

in people with normal fasting but elevated post-prandial glucose levels, diagnose according to 2-h OGTT criteria