Diabetes mellitus is defined as a metabolic disorder of multiple aetiology characterised by chronic hyperglycaemia (raised glucose levels) 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 (excessive urination), polydipsia (excessive water drinking) and unexplained weight loss and is confirmed by documented hyperglycaemia.
The clinical presentation of diabetesranges from asymptomatic (no symptoms) in type 2 diabetes to the dramatic life threatening conditions of diabetic ketoacidosis (a complication of poor glucose control). Patients may also present with ischaemic heart disease, stroke and peripheral vascular disease or retinopathy (eye damage), nephropathy (kidney damage) and neuropathy (nerve damage)
CLASSIFICATION
Diabetes can be classified into four clinical categories:
Type 1 diabetes (due to b-cell destruction, usually leading to absolute insulin deficiency)
Type 2 diabetes (due to a progressive insulin secretory defect on the background of insulin resistance)
Other specific types of diabetes due to other causes, e.g., genetic defects in b-cell function, genetic defects in insulin action, diseases of the exocrine pancreas (such as cystic fibrosis), and drug- or chemical-induced (such as in the treatment of HIV/AIDS or after organ transplantation)
Gestational diabetes mellitus (GDM) (diabetes diagnosed during pregnancy that is not clearly overt diabetes)
DIAGNOSIS
Diabetes is usually diagnosed based on plasma glucose criteria, either the Fasting Plasma Glucose (FPG ?126mg/dl or 7.0mmol/l) or
The 2-h plasma glucose (2-h PG ?200mg/dl or 11.1mmol/l) value after a 75-g oral glucose tolerance test (OGTT).
Recently, an International Expert Committee added the A1C (threshold ? 6.5%) as a third option to diagnose diabetes.
In a patient with classic symptoms of hyperglycaemia (thirst, polyuria, or polyphagia and weight loss) hyperglycaemia crisis, a casual plasma glucose ?200mg/dl is diagnostic. In the absence of unequivocal hyperglycaemia, the result should be confirmed by repeat testing. In the absence of symptoms, two abnormal results (ie two raised fasting levels) or an abnormal OGTT result is diagnostic.
Categories of Increased Risk for Diabetes (Prediabetes)
In 1997 and 2003, the Expert Committee on Diagnosis and Classification of Diabetes Mellitus recognized a group of individuals whose glucose levels did not meet the criteria for diabetes, but were too high to be considered normal. These persons were defined as having impaired fasting glucose (IFG) (FPG levels 100–125mg/Dl [5.6–6.9 mmol/L]), or impaired glucose tolerance (IGT) (2-h PG OGTT values of 140–199 mg/dL [7.8–11.0 mmol/L]).
“Prediabetes” is the term used for individuals with IFG and/or IGT, indicating the relatively high risk for the future development of diabetes. IFG and IGT are associated with obesity (especially abdominal or visceral obesity), dyslipidemia with high triglycerides and/or low HDL cholesterol, and hypertension.
TESTING FOR DIABETES IN ASYMPTOMATIC PATIENTS
Recommendations
Testing to detect type 2 diabetes and prediabetes in asymptomatic people
should be considered in adults of any age who are overweight or obese (BMI ? 25 kg/m2) and who have one or more additional risk factors for diabetes. In those without these risk factors, testing should begin at age 45 years. If tests are normal, repeat testing at least at 3-year intervals is reasonable. To test for diabetes or prediabetes, the A1C, FPG, or 2-h 75-g OGTT are appropriate.
In those identified with prediabetes, identify and, if appropriate, treat other CVD risk factors. The same tests are used for both screening and diagnosing diabetes.
Diabetes may be identified anywhere along the spectrum of clinical scenarios: from a seemingly low-risk individual who happens to have glucose testing, to a higher-risk individual whom the provider tests because of high suspicion of diabetes, and finally, to the symptomatic patient. The discussion herein is primarily framed as testing for diabetes in asymptomatic individuals. The same assays used for testing will also detect individuals with prediabetes.
PREVENTION/DELAY OF TYPE 2 DIABETES
Recommendations
Patients with IGT, IFG, or an A1C 5.7–6.4% E should be referred to an effective ongoing support program targeting weight loss of 7% of body weight and increasing physical activity to at least 150 min/week of moderate activity such as walking. Follow-up counseling appears to be important for success. Based on the cost-effectiveness of diabetes prevention, such programs should be covered by third-party payers (Health Insurance).
Metformin therapy for prevention of type 2 diabetes may be considered in those with IGT, IFG, or an A1C 5.7–6.4% E, especially for those with BMI 35 kg/m2, aged, 60 years, and women with prior GDM.
At least annual monitoring for the development of diabetes in those with prediabetes is suggested. Screening for and treatment of modifiable risk factors for CVD is suggested.
RCTs have shown that individuals at high risk for developing type 2 diabetes (IFG, IGT, or both) can significantly decrease the rate of diabetes onset with particular interventions. These include intensive lifestyle modification programs that have been shown to be very effective (; 58% reduction after 3 years) and pharmacological agents metformin, a-glucosidase inhibitors, orlistat, and thiazolidinediones, each of which has been shown to decrease incident diabetes to various degrees.
Follow-up of all three large studies of lifestyle intervention has shown sustained reduction in the rate of conversion to type 2 diabetes, with 43% reduction at 20 years in the Da Qing study, 43% reduction at 7 years in the Finnish Diabetes Prevention Study (DPS), and 34% reduction at 10 years in the U.S. Diabetes Prevention Program Outcomes Study (DPPOS).
Given the clinical trial results and the known risks of progression of prediabetes to diabetes, persons with an A1C of 5.7–6.4%, IGT, or IFG should be counseled on lifestyle changes with goals similar to those of the DPP (7% weight loss and moderate physical activity of at least 150 min/week). Metformin has a strong evidence base and demonstrated long-term safety as pharmacological therapy for diabetes prevention. For other drugs, cost, side effects, and lack of a persistent effect require consideration.
Metformin
Metformin was less effective than lifestyle modification in the DPP and DPPOS, but may be cost-saving over a 10-year period. It was as effective as lifestyle modification in participants with a BMI ? 35 kg/m2, but not significantly better than placebo in those over age 60 years. In the DPP, for women with a history of GDM, metformin and intensive lifestyle modification led to an equivalent 50% reduction in diabetes risk.
Metformin therefore might reasonably be recommended for very-high-risk individuals (e.g., history of GDM, very obese, and/or those with more severe or progressive hyperglycemia). People with prediabetes often have other cardiovascular risk factors, such as obesity, hypertension, and dyslipidemia, and are at increased risk for CVD events. While treatment goals are the same as for other patients without diabetes, increased vigilance is warranted to identify and treat these and other risk factors (e.g., smoking).
INITIAL DIETARY ADVICE FOR NEWLY DIAGNOSED PATIENTS WITH DIABETES
- Quench thirst with water, or low calorie carbonated drinks
- Avoid sugar and obviously sugary foods
- Use artificial sweeteners in beverages
- Cereal, bread, or potatoes should form main part of each meal
- Meat should be grilled rather than fried, same with other food
- Fish and poultry are good alternatives to meat
- Eat plenty of fresh fruits and vegetables
- Use cooking oils low in saturated fats-olive oil
- Moderate your alcohol consumption
- Avoid adding salt to food at the table especially if hypertensive
Dr Ofem Enang is a Consultant Endocrinologist with the University of Calabar Teaching Hospital, Calabar. Nigeria.
