1.1 Background

Diabetes mellitus is a major and increasing health problem in all age groups in Scotland. Diabetes UK estimates that of a population of 5.2 million in Scotland in the year 2000, 122,900 people had confirmed diabetes mellitus and a further 87,100 were undiagnosed, giving a total of 210,000 people with diabetes. Accurate national prevalence data is unknown, but data from the Tayside Diabetes Registry suggests that the prevalence is over 2.6% and rising. Type 2 diabetes, in particular, is a growing problem with a rapidly increasing prevalence due to the ageing population and the increasing incidence of obesity.¹ It is now being recognised in adolescents and young adults.

Diabetes is still the commonest cause of blindness in the working population. 20-25% of patients entering end-stage renal failure replacement programmes have diabetes. Foot problems are the commonest cause of admission to hospital in patients with diabetes, with a 15-20 fold increased risk of amputation. The life expectancy of a patient with type 2 diabetes is reduced by 8-10 years, and atherosclerotic vascular disease, especially coronary artery disease and stroke, is the principal cause of death in about 70% of these patients. Pregnancy in women with diabetes has a poorer outcome for the fetus than a non-diabetic pregnancy. Children and adolescents with diabetes present difficulties in management, requiring a multidisciplinary team approach.

1.2 Reviewing the original guidelines

The original six SIGN guidelines for diabetes were published in 1996-97 and dealt with visual impairment (SIGN 4), pregnancy (SIGN 9), children and young people (SIGN 10), renal disease (SIGN 11), foot disease (SIGN 12) and cardiovascular disease (SIGN 19). In addition, SIGN published in 1998 a recommended minimum dataset for collection in people with diabetes (SIGN25).

The guidelines have been widely accepted by all professionals responsible for diabetes care in Scotland and many of the guideline recommendations have been adopted in other countries. However, in keeping with SIGN's commitment to update its evidence-based guidelines in the light of emerging evidence, it was agreed that the original guidelines should be reviewed. This has provided an opportunity to review the remit of the guidelines and a new section dealing with lifestyle has been introduced. The seven aspects of care now covered are published here as one SIGN guideline on diabetes mellitus. Further information, where appropriate, is available from the SIGN website at http://www.sign.ac.uk

In September 2000, the Working Group on IT to Support Shared Care in Diabetes published a document which laid out principles of support and promotion of integrated care for patients with diabetes and also discussed the data collection required in the clinical management of these patients. This group published an extended dataset, based on SIGN 25, which was felt to be more useful for recording information directly relevant to active clinical care than the SIGN document which was felt to be most useful for population-level registers.² For this reason, the SIGN minimum dataset has not been reviewed in this document.

1.3 The aim of the guideline

The aim has been to provide an updated evidence-based approach to influence current practice in order to reduce the burden of long-term complications, both microvascular and macrovascular, as well as improve pregnancy outcome for the mother with diabetes. The guideline also incorporates the new World Health Organisation diagnostic criteria for diabetes mellitus which were implemented in the UK in June 2000.

1.4 National diabetes initiatives

The Scottish National Health Plan "Our National Health", published in December 2000 gave a commitment that the Scottish Executive would publish a Scottish Diabetes Framework by the end of 2001. The Clinical Standards Board for Scotland will identify clinical standards for diabetes services. These standards will be fully aligned with the Framework. The revised SIGN diabetes guideline will be the cornerstone of evidence-based clinical practice for the Framework and the standards to move forward the improvement of diabetes care in Scotland.

1.5 Definition and diagnosis of diabetes mellitus

Diabetes mellitus is defined as a metabolic disorder of multiple aetiology characterised by chronic hyperglycaemia with disturbances of carbohydrate, protein and fat metabolism resulting from defects in insulin secretion, insulin action, or both. The clinical diagnosis of diabetes is often indicated by the presence of symptoms such as polyuria, polydipsia, and unexplained weight loss, and is confirmed by measurement of abnormal hyperglycaemia. ³

WHO³ advises that the range of blood glucose indicative of diabetes mellitus are as follows:*

• random venous plasma glucose >= 11.1 mmol/l; or
• fasting plasma glucose (FPG) >= 7.0 mmol/l; or
• plasma glucose >= 11.1 mmol/l at two hours after a 75g oral glucose load (oral glucose tolerance test (OGTT)).

Although patients with type 1 diabetes usually present with characteristic symptoms and should be immediately referred to specialist diabetes care upon diagnosis, for the asymptomatic individual, at least one additional plasma glucose with a value in the diabetic range above is essential to diagnose diabetes accurately. This may be from a fasting (casual sample) or from an OGTT.

1.6 Statement of intent

This guideline is not intended to be construed or to serve as a standard of medical care. Standards of care are determined on the basis of all clinical data available for an individual case and are subject to change as scientific knowledge and technology advance and patterns of care evolve. These parameters of practice should be considered guidelines only. Adherence to them will not ensure a successful outcome in every case, nor should they be construed as including all proper methods of care or excluding other acceptable methods of care aimed at the same results. The ultimate judgement regarding a particular clinical procedure or treatment plan must be made in light of the clinical data presented by the patient and the diagnostic and treatment options available. However, it is advised that significant departures from the national guideline or any local guidelines derived from it should be fully documented in the patient's case notes at the time the relevant decision is taken.

1.7 Review and updating

This guideline was issued in 2001 and will be considered for review in 2004, or sooner if new evidence becomes available. Any updates to the guideline in the interim period will be noted on the SIGN website: http://www.sign.ac.uk

* Impaired Glucose Tolerance (IGT) is a stage of impaired glucose regulation (FPG <7.0 mmol/l and OGTT 2 hour value >= 7.8 mmol/l but <11.1mmol/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).

IGT and IFG are not clinical entities in their own right, but rather risk categories for cardiovascular disease (IGT) and/or future diabetes (IFG).