Diabetes Prevalence & HbA1c Testing

What is Diabetes?

Diabetes is a disease in which the body does not produce or properly use insulin. Insulin is a hormone that is needed to convert sugar, starches and other food into energy needed for daily life. The result is hyperglycemia or high blood glucose. The cause of diabetes continues to be a mystery, although both genetics and environmental factors such as obesity and lack of exercise appear to play roles. (ADA source)

The World Health Organization¹ recognizes three main forms of diabetes, which have similar signs, symptoms, and consequences, but different causes and population distributions:

• Type 1
• Type 2
• Gestational diabetes

Ultimately, all forms are due to the beta cells of the pancreas being unable to produce sufficient insulin to prevent hyperglycemia.

• According to the American Diabetes Association (ADA), 20.8 million children and adults, or 7% of Americans, have Diabetes. ²
• The global projection for the year 2025 is 333 million (larger than the US population). ²
• Measurement of percent HbA1c is the method of choice for monitoring therapy of patients with diabetes. ³
• The ADA recommends that all people with diabetes have their HbA1c level tested 2-4 times per year. ⁴

Type 1 Diabetes Mellitus

Diabetes mellitus type 1 is a form of diabetes mellitus, also known as Childhood Diabetes (juvenile diabetes). Type 1 diabetes is an autoimmune disease that results in the permanent destruction of insulin-producing beta cells of the pancreas. Loss of the insulin-producing beta cells of the islets of Langerhans of the pancreas lead to a deficiency of insulin.

Type 1 diabetes comprises up to 10% of total diabetes cases in North America and Europe, although this varies by geographical location. Currently, type 1 diabetes can be treated only with insulin. Diet and exercise cannot reverse or prevent type 1 diabetes, however, a proper diet and adequate exercise can help a person with diabetes maintain good glycemic control.

Type 2 Diabetes Mellitus

Type 2 diabetes mellitus, previously known as adult-onset diabetes, is a combination of defective insulin secretion and insulin resistance or reduced insulin sensitivity. It is often managed by engaging in exercise and modifying one's diet. Obesity is found in approximately 55% of patients diagnosed with type 2 diabetes. Other factors include aging and family history. Type 2 diabetes constitutes about 85-95% of diabetes in developed countries. It is usually first treated through increased physical activity, improved diet, and weight loss. When exercise and diet do not make a difference, the usual next step is treatment with oral anti-diabetic drugs. When oral medications fail, insulin therapy will be necessary to maintain normal or near normal glucose levels.

Gestational Diabetes Mellitus

Gestational diabetes (GDM) is a condition in which women who have not been previously diagnosed with diabetes exhibit high blood glucose levels during pregnancy. This occurs in about 2%–5% of all pregnancies, and may improve or disappear after delivery.  It involves a combination of inadequate insulin secretion and responsiveness, resembling type 2 diabetes in several respects. Gestational diabetes may damage the health of the fetus or mother, and about 20%–50% of women with gestational diabetes develop type 2 diabetes later in life.

Fetal/neonatal risks associated with GDM include congenital anomalies such as cardiac, central nervous system, and skeletal muscle malformations. In severe cases, the fetus may die.

About Glucose Metabolism

Much of the carbohydrate in food is converted within a few hours to the monosaccharide glucose, the principal carbohydrate found in blood. Muscle and liver cells use glucose to make energy. Fat cells use glucose to make triglycerides. Glucose cannot get into the cells without insulin.

If there isn’t enough insulin available, or if cells respond poorly to the insulin (insulin insensitivity or resistance), glucose will not be handled properly by body cells or stored appropriately in the liver and muscles.

The net effect is persistent high levels of blood glucose, poor protein synthesis, and other metabolic disorders, such as acidosis.

Use of HbA1c Determination

A red blood cell (RBC) is freely permeable to glucose in the blood. The glucose in the RBC will bind to hemoglobin in the RBC. Studies have shown that the higher the glucose concentration is in the blood, the more glucose is bound to hemoglobin. Hemoglobin that has glucose bound to it is called Glycated Hemoglobin (GHB), Glycosylated Hemoglobin, or HbA1c. The amount (or percentage) of hemoglobin that is bound with glucose is traceable to the average blood glucose level over the life span of the RBC.

Red cell life span is normally ~100-120 days
– The degree of glycation of hemoglobin gives a picture of average blood glucose levels for the previous three month period. 

HbA1c is primarily used as a treatment-tracking test
– Most labs consider a glycated hemoglobin of greater than 6% to be abnormal or elevated.
– Some physicians may order this test at the time of diagnosis to track changes over time.

The current recommended goal for HbA1c in patients with diabetes is <7.0%⁵, which as defined as "good glycemic control", although some guidelines are stricter (<6.5%)^6,7.
– People with diabetes who have HbA1c levels within this range have a significantly lower incidence of complications from diabetes, including retinopathy and diabetic nephropathy.

Relationship Between Blood Glucose and HbA1c*

Each 1% change in GHB represents a change of approximately 35 mg/dL mean plasma glucose or 2.0 mmol/L.

Please note that this relationship applies only to GHB methods certified as traceable to the Diabetes Control and Complications Trial (DCCT) reference, and that it is based on overall averages and may vary slightly in individual patients.

** Mean blood glucose results are 10-15% lower. Most blood glucose meters are calibrated to read as plasma glucose.
*Adapted from: Rohlfing et al. Diabetes Care, vol 25, 2, 2002

REFERENCES

1. WHO. Definition, Diagnosis and Classification of Diabetes Mellitus and Its Complications, Report of a WHO Consultation, Part 1, 1999
2. Diabetes Trends, Clinical Lab Products, August 2007
3. AxSYM HbA1c US Package Insert
4. Lab Tests Online
5. Goldstein DE, Little RR, Lorenz RA, et al. American Diabetes Association. Tests of Glycemia in Diabetes. Diabetes Care 2003;26(1): S106–8
6. International Diabetes Federation, Clinical Guidelines Task Force, Global Guideline for Type 2 Diabetes, Chapter 6, 2005
7. AACE Diabetes Mellitus Guidelines, Endocr Pract. 2007;13 (Suppl 1) 2007 17