Diabetes Indicators

Glucose homeostasis is generally determined by analysis of HbA_1c levels. However, this parameter is an integration of FPG and PPG variations over 2-3 months. Debate continues over precisely which of these three parameters (HbA_1c, FPG, and PPG) is most applicable for the determination of glycaemic control. Current opinions suggest the best assessment of glucose homeostasis is provided by the determination of all three components of glycaemic state.⁴

HbA_1c

HbA_1c or glycosylated haemoglobin is a measurement which shows how much glucose has bound to red blood cells over the previous 2-3 months. It is the best indicator of long-term glucose control, and is considered the core measurement for evaluating glycaemic control and assessing quality of diabetes care. It is expressed as a percentage with lower values indicating better glycaemic control.

American Diabetes Association (ADA) guidelines recommend a mean HbA_1c goal of ≤7.0%,⁵ while the International Diabetes Federation (IDF) recommends a limit of 6.5%.⁶

The UK Prospective Diabetes Study (UKPDS) showed that lowering mean HbA_1c by 1% was associated with a 14% decreased risk of heart attack, a 37% decreased risk of microvascular complications, and a 21% decrease in diabetes-related deaths.⁷

Fasting plasma glucose (FPG)

Fasting is a state achieved after a period of eight hours without food or drink, other than water, and is often requested prior to receiving a test for diabetes. In everyday life the ‘real’ fasting period is probably only limited to a 3- to 4-hour period of time towards the end of the night.⁴

During fasting, the hormone glucagon is stimulated, resulting in an increase in plasma glucose levels. It is these levels which are analysed during a carbohydrate metabolism test to give an indication of glycaemic control. Individuals without diabetes produce insulin to balance the increase in glucose levels; however, people with diabetes are less able to do this (depending upon disease type and progression) and will record higher plasma glucose levels during the test.

For people with type 2 diabetes, the American Diabetes Association (ADA 2004) recommends a fasting plasma glucose goal of 70–130 mg/dl (3.9–7.2 mmol/l)⁵ and the International Diabetes Federation set the goal at <100 mg/dl (6.0 mmol/l).⁶

Much emphasis is placed upon fasting plasma glucose and HbA_1c measurements to guide the management of diabetes; however, several observational studies have indicated that plasma glucose testing at postprandial time points (PPG), may be equally, if not more important for monitoring and controlling diabetes.^8,9,10

Postprandial plasma glucose (PPG)

Postprandial plasma glucose concentrations refer to plasma glucose concentrations following a meal. Plasma glucose concentration will increase approximately 10 minutes after starting a meal due to the absorption of carbohydrates from the food. This absorption, along with insulin and glucagon secretion and their coordinated effects on glucose metabolism, govern the profile of PPG. Individuals without diabetes show peak plasma glucose concentrations after 60 min and these rarely exceed 140 mg/dl (7.8 mmol/l) and pre-prandial levels are achieved within 2-3 hours. Individuals with type 1 diabetes can only control PPG levels by insulin administration prior to, or at, mealtimes. In people with type 2 diabetes who are not dependent on insulin, insulin secretion is delayed and/or insufficient and therefore PPG control may not be adequately achieved.

PPG determination is generally performed 2 hours after the start of a meal. This generally approximates to the peak value in postprandial with diabetes and provides a reasonable assessment of postprandial hyperglycaemia.¹¹

As with FPG, attempts have been made to establish a consensus on target levels for PPG. Unfortunately, unlike with FPG targets, large discrepancies exist between associations.⁴ The American Diabetes Association has set the postprandial glycaemic target value below 180 mg/dl (10.0 mmol/l),⁵ whereas the International Diabetes Federation recommends that postprandial glucose values be maintained below 160 mg/dl (9.0 mmol/l).⁸

[x] Close

BMI is an indirect measure of body fat calculated from a person’s weight and height. The formula for BMI is weight in kilograms divided by height in meters squared: weight (kg) / [height (m)]²

For adults aged 20 years and older, BMI is interpreted using standard weight status categories (e.g., underweight, normal, overweight, obese) that are the same for all ages and for both men and women. For children and teens, the interpretation of BMI is both age- and gender-specific.

Excess weight is an independent risk factor for cardiovascular disease, even in people without diabetes.¹² Based on a comprehensive review of the literature, researchers have estimated that for every unit of BMI gained, the risk of coronary heart disease increases by 9-16% in the general population.¹³

Modest weight loss can improve insulin resistance, glycaemic control, and cardiovascular risk profile in people with diabetes.^14,15

[x] Close

Blood pressure is the force exerted by circulating blood on the walls of blood vessels. High blood pressure can lead to coronary heart disease, heart failure, stroke and renal failure, among other medical conditions. Among patients with diabetes, hypertension is associated with an 82% increase in the risk of diabetes-related mortality.¹⁷ Controlling and reducing blood pressure can reduce risks of cardiovascular disease (e.g., heart disease and stroke) by approximately 33-50% and microvascular complications of diabetes by approximately 37%.¹⁸

In general, the risk for any diabetes-related complication is reduced by 12% for every 10 millimetres of mercury (mm Hg) reduction in systolic blood pressure. ¹⁹ It is important to note that tight control of blood pressure must be maintained to achieve this risk reduction.¹⁷

[x] Close

Cholesterol is present in certain foods and is also produced by the liver. There are two types of cholesterol: HDL, also referred to as ‘good cholesterol,' and LDL, also referred to as ‘bad cholesterol.' Triglycerides are the chemical form in which most fat exists in food and in the body. They are also present in blood plasma and, in association with cholesterol, form the plasma lipids.

[x] Close

Quality of Life is an important health outcome for patients with diabetes, and it is intimately related to glycaemic control and the presence of diabetes-related complications.²⁰ There is strong evidence that psychosocial issues (health beliefs, social support, coping strategies, and personality traits) are critical to good diabetes care.²¹ Such variables are often considered stronger predictors of medical outcomes than traditional indicators such as HbA_1c and BMI.²²

Two approaches to quantifying health-related QoL exist: generic and disease specific. Generic approaches measure factors which are applicable across all health and illness groups. Disease specific approaches take into account certain aspects of a particular disease which are critical to an individual’s health-related QoL. In the case of diabetes these aspects would include hypoglycaemia, insulin injections and self-monitoring of blood glucose, among others.²⁰

The most widely used measure of quality of life in diabetes is the Diabetes Quality of Life (DQoL) measure developed for use in the Diabetes Control and Complications Trial.²³ Other diabetes-specific QoL measures have also been developed and are used to address different aspects of the disease. Further information on diabetes-specific QoL measures can be found in a publication by Watkins²⁴ which reviews many of the specific diabetes QoL measures.

[x] Close