Summary of Changes
The World Health Organisation has now published the revised ‘Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications’, and these are now ready for implementation. The changes to the classification and definition of diabetes are a result of epidemiological studies which have shown that there is a closer relationship between a fasting glucose value of 7mmol/l and the two hour value of 11.1mmol/l
Diabetes UK recommends that all healthcare professionals adopt this new criteria from 1 June 2000.
The main changes of the new recommendations are set out below. They include the recommendation that the cut off point for diagnosing diabetes using a fasting plasma glucose should be lowered from 7.8 mmol/l to 7.0 mmol/l. This change reflects research evidence regarding the development of the complications of diabetes.
For a copy of the full report simply download into word ‘Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications’ from the related information box
Methods and criteria for diagnosing diabetes mellitus
1. Diabetes symptoms (ie polyuria, polydipsia and unexplained weight loss) plus
- a random venous plasma glucose concentration 11.1 mmol/l
or
- a fasting plasma glucose concentration 7.0 mmol/l (whole blood 6.1mmol/l)
or
- two hour plasma glucose concentration 11.1 mmol/l two hours after 75g anhydrous glucose in an oral glucose tolerance test (OGTT).
2. With no symptoms diagnosis should not be based on a single glucose determination but requires confirmatory plasma venous determination. At least one additional glucose test result on another day with a value in the diabetic range is essential, either fasting, from a random sample or from the two hour post glucose load. If the fasting or random values are not diagnostic the two hour value should be used
Classification and terms
- Insulin-dependent (IDDM) and non-insulin dependent diabetes (NIDDM) will be renamed Type 1 and Type 2 diabetes
- The terms Type 1 and Type 2 process will be introduced to describe the cause of insulin dependent and non-insulin dependent diabetes respectively. Both of these pathological processes will be clinically staged by the treatment that they need – from diet to insulin
- Impaired Glucose Tolerance (IGT)* is a stage of impaired glucose regulation (Fasting plasma glucose 7.0 mmol/ and OGTT two hour value 7.8mmol/l but 11.1 mmol/l).
- Impaired Fasting Glycaemia (IFG)* has been introduced to classify individuals who have fasting glucose values above the normal range but below those diagnostic of diabetes. (Fasting plasma glucose 6.1 mmol/l but 7.0 mmol/l). Diabetes UK recommends that all those with IFG should have an OGTT to exclude the diagnosis of diabetes, and are actively managed with lifestyle advice.
- New: Gestational diabetes is retained but now encompasses the groups formerly classified as Gestational Impaired Glucose Tolerance (GIGT) and Gestational Diabetes Mellitus (GDM). Diabetes UK endorses the use of the WHO definition to allow for comparative studies. However, since glucose tolerance changes with the duration of pregnancy, the gestation at which the diagnosis was made should be recorded and, if made in the third trimester, the clinician should be cautious about the clinical implication of impaired glucose. Some concern has been expressed that the WHO level may be too tight for everyday clinical practice and the Diabetes Care Advisory Committee (DCAC) is currently consulting on revised recommendations. In the meantime, the DBA recommends that clinicians use their own clinical judgement when diagnosing Gestational diabetes in practice.
- It should be noted that children usually present with severe symptoms and diagnosis should then be based on a single raised blood glucose result, as above. Immediate referral to a Paediatric Diabetes Team should not be delayed.
A diagnosis of diabetes has important legal and medical implications for the patient and it is therefore essential to be secure in the diagnosis. A diagnosis should never be made on the basis of glycosuria or a stick reading of a finger prick blood glucose alone, although such tests may be useful for screening purposes. HbA1c measurement is also not currently recommended for the diagnosis of diabetes.
Diabetes UK recommends that the diagnosis is confirmed by a glucose measurement performed in an accredited laboratory on a venous plasma sample, although the WHO do give values for whole blood as well. This should mean that there is less need to perform oral glucose tolerance testing on the majority of the population, although in the elderly and some ethnic minority groups the fasting glucose may not be a reliable indicator of diabetes. For this group, and in the absence of symptoms of diabetes, Diabetes UK would recommend the use of a glucose tolerance test as the definitive second test.
Obviously there is some concern about the implications of these changes for diabetes care. The new criteria have simplified the diagnosis of diabetes and the ability to diagnose cardiovascular high risk cases in many people. Earlier diagnosis will increase the total number of people with diabetes, but if they are managed according to Diabetes UK guidelines, may of these new cases will be diet controlled. In the long term, complications should be lessened to the benefit of the individual and to the health service.
*IGT and IFG are not clinical entities in their own right, but rather risk categories for cardiovascular disease and/or future diabetes.