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| Issue 7 2000 |  |
| DIABETES MELLITUS |
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Dr Greg Fulcher Endocrinology, PaLMS Contact: tel +61 2 9926 8388 e-mail: gfulcher@med.usyd.edu.au |
| Diabetes
Mellitus: Extent of the problem Diabetes mellitus is a common medical problem. Although accurate data are lacking, it has been estimated that the prevalence in adult Caucasians varies from 2-7% while that in the Aboriginal population is between 5-19%. In addition, diabetes is an age-related disorder and over the age of 65 years an 8-10% prevalence rate is described. In certain populations such as Pacific Islanders, people from the Middle East, Southern Europe and Asia, the rates are even higher. Much of the data has relied on the “self-reporting” of the presence of diabetes or “high blood sugar” and there are few firm estimates of the extent of undiagnosed diabetes. In the 1976-80 National Health and Nutritional Examination Survey in the United States the prevalence of diagnosed and undiagnosed diabetes was equivalent. Based on an estimate of 350-400,000 patients known to have diabetes in Australia, the same number remains unrecognised creating a major public health challenge. Most of these people have Type 2 diabetes (see Table 1. below). By contrast, Type 1 is relatively less common. The 1990-91 estimate was 14.5 per 100,000 person years and the 1992-96 estimate 19.2 per 100,000 person years. |
| Type 1 | (B-cell destruction, usually leading to absolute insulin deficiency) Autoimmune |
| Type 2 | (ranging from either predominantly insulin resistance with relative insulin deficiency to a predominantly secretory defect with or without insulin resistance) |
| Other Specific Types |
Genetic defects of B-cell function Genetic defects in insulin action Diseases of the exocrine pancreas Endocrinopathies Drug or chemical inducedinfections |
| Gestational Diabetes |
| Classification of Diabetes and Categories of Glucose regulation There have been a number of sets of diagnostic criteria proposed for diabetes. These include the 1979 National Diabetes Data Group (NDDG) classification, the report of the 1980 World Health Organisation (WHO) Expert Committee on Diabetes and later the WHO Study Group on Diabetes. In 1997 the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus published a revised classification and new diagnostic criteria for diabetes (Diabetes Care 1997: 20; 1183-1197) (Table 1) while in 1999 an Australian Working Party published the classification and criteria for the diagnosis of Diabetes Mellitus (MJA 1999: 170; 375-378. A New Classification and Criteria for the Diagnosis of Diabetes Mellitus). The major changes incorporated in the recently published criteria are:
The revised criteria for diabetes mellitus are presented in Table 2. The major change from previous recommendations is the lowering of the diagnostic level of fasting plasma glucose to 7.0mmol/L (previously 7.8mmol/L). This change is based on cross-sectional studies that have shown microvascular complications at these lower glucose concentrations and the fact that a fasting plasma glucose level of >=7.0mmol/L accords more closely with a 2hr post-glucose level of 11.1mmol/L. It is important to note that the diagnostic criteria differ between clinical and epidemiological settings. For a patient with typical symptoms, either a fasting plasma glucose of >=7.0mmol/L or random/2h post-glucose plasma glucose level of >=11.1mmol/L is sufficient to establish the diagnosis. In the absence of symptoms, one additional glucose measurement in the diabetic range is necessary to confirm the diagnosis. In patients with acute infection, trauma or other stresses, an elevated glucose level should not be considered diagnostic of diabetes and the patient should be re-evaluated when the acute physiological stress has resolved. In epidemiological settings, a single measure, the glucose level 2h post-glucose load will suffice. The category of impaired glucose tolerance refers to a fasting plasma glucose of <7.0mmol/L with a two-hour value on glucose tolerance testing >=7.8 and <11.1mmol/L . An additional category of impaired fasting glucose is defined by a fasting plasma glucose >= 6.1 mmol/L and <7.0 mmol/L and a two hour value on an oral glucose tolerance test (OGTT) of <7.8mmol/L. |
| 1. | Symptoms of diabetes plus casual plasma glucose concentration >11.1mmol/L. (The classic symptoms of diabetes include polyuria, polydipsia and unexplained weight loss.) |
| OR | |
| 2. | Fasting plasma glucose >= 7.0mmol/L (fasting is defined as no caloric intake for at least 8 hours.) |
| OR | |
| 3. | 2 hour plasma glucose >= 11.1mmol/L during an OGTT. (The test should be performed using a 75g glucose load.) |
| The role of the OGTT
At present there is dissent between the American Diabetes Association (ADA) and the WHO with respect to the role of the OGTT. The ADA strongly recommends reliance on the fasting plasma glucose levels and a decreased role for the OGTT. The WHO strongly believes the OGTT should be retained, a view supported by the Australasian Working Party. Complications The community burden of diabetes is substantially determined by the prevalence of complications. These affect the eyes (leading to diabetic retinopathy and blindness), kidneys (leading to renal impairment and failure) and nervous system (leading to neuropathy, foot ulcers, amputation and impotence in men). Macrovascular complications, the major cause of morbidity and mortality in patients with Type 2 diabetes, are due to accelerated atherosclerosis and include coronary heart disease, stroke and peripheral vascular disease. The prevalence of retinopathy ranges from 21-36% and vision threatening retinopathy is estimated at 5-13%. According to the United Kingdom Prospective Diabetes Study (UKPDS), neuropathy exists in 7% of patients with Type 2 diabetes and in a Scandinavian population 20-25% have microalbuminuria, a precursor of diabetic nephropathy and an independent risk factor for cardiovascular disease. At least 50% of all deaths are due to coronary heart disease and a further 15% to cerebrovascular disease. People with Type 2 diabetes develop heart disease at a younger age, are more likely to have multivessel disease and more extensive atherosclerosis. In one study, the risk of a diabetic patient with no previous infarct having a cardiac event was equivalent to that of a non-diabetic with known coronary artery disease. Outcomes following myocardial infarction are worse. The costs of these complications, both personal and to the community are high. For example it has been estimated that the total cost of diabetes in the year 2000 will be between AUD $730 million and $1.85 billion. Management The Diabetes Control and Complications trial clearly established that an intensive management protocol could substantially decrease the microvascular complications in patients with Type 1 diabetes. By contrast the effects on macrovascular disease did not reach statistical significance. The UKPDS extended these findings to patients with Type 2 diabetes, but once again emphasised that a strategy based solely on glycaemia would only minimally impact on macrovascular disease. To date the most effective strategy to decrease macrovascular complications has been the treatment of dyslipidaemia with simvastatin therapy (the 4S study). The importance of tight control of blood pressure has also been emphasised in both the UKPDS and the recently published Hypertension Optimal Treatment (HOT) study. In the UKPDS, “tight” control of blood pressure (to a mean value of 144/82) reduced the risk of all diabetes-related end-points by 24%, deaths by 32% and the risks of microvascular complications, including retinopathy and nephropathy, by 37%. While there are clear metabolic and theoretical physiological advantages to the use of ACE inhibitors, the somewhat surprising finding was that the beta-blocker atenolol was equally as effective as the ACE inhibitor captopril in the prevention of both retinopathy and nephropathy. |
The messages for the management of most patients with diabetes are therefore:
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| August
is shaping up to be a memorable month for PaLMS with implementation
of a new service, anniversary celebrations and our first symposium.
The PaLMS Courier Service was mentioned in our last issue. The final stages of planning are complete and implementation is in progress. The PaLMS Courier Service will commence on August 14 with Jason Boyd as the Courier Coordinator. To discuss your courier requirements, contact Jason via the PaLMS Service Centre on 9926 6066. We are also celebrating the first anniversary of the PaLMS Collection Suite at North Shore Private Hospital. To make this a truly memorable occasion we will be running a Respiratory Symposium at NSPH on August 31, with Professor Bryan Corrin from the UK as our keynote speaker. Seats at the Respiratory Symposium are limited so please get in early with your bookings. Contact Jane Flynn on 8425 3153 to reserve a place. We hope that you can come along and help us celebrate our first twelve months at NSPH. Professor Corrin will also be speaking on Saturday August 28 at a Symposium arranged by Hunter Area Pathology Service. For more information on the HAPS Symposium, contact Cathy-Lyn Burnard on 02 4921 4980. The Respiratory Symposium is the first in a series of PaLMS symposia which, in response to your suggestions in the recent PaLMS Education Survey, will include topics such as Hypertension & Renal Medicine and Reproductive Testing & Infertility.  PaLMS Customer Relations Manager tel: +61 2 9926 8086 email: mhardy@doh.health.nsw.gov.au |
| PaLMS STAFF
Robert Flower Robert Flower, Scientific Head of Transfusion, PaLMS, has recently received an adjunct appointment as Associate Professor in the Department of Haematology and Transfusion, University of Sydney. The Australian Institute of Medical Scientists has also awarded Robert the John Whiteley Award for initiatives in continuing education in the area of Molecular Informatics ie. training us in the use of the internet to recover information about the molecular structure of proteins and peptides of clinical interest. Together with Drs James Isbister and Jonathon Morris, Robert is writing an article for InfoLink on "Haemolytic Disease of the Newborn and Guidelines for the Use of Anti-D". |
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Renze Bais,
the Head of PaLMS Express Services has recently been elected Secretary
of Clinical Biochemistry´s international body, the International Federation
of Clinical Chemistry and Laboratory Medicine. Renze was the author of a recent InfoLink article on " New Markers for Coronary Artery Disease" and, together with Professor Leslie Burnett, the Director of PaLMS, has coauthored a chapter on Point of Care Testing in a book to be published by the American Association of Clinical Chemistry. |