Diabetes - Diagnosis Tests For Type 2 Diabetes

Originally Published Sept 2007

WHAT ARE THE SYMPTOMS OF TYPE ll DIABETES?

Type ll diabetes usually begins gradually and progresses slowly. Symptoms in adults include the following:

Excessive thirst.
Increased urination.
Fatigue.
Blurred vision.
Weight loss.
In women, vaginal yeast infections or fungal infections under the breasts or in the groin.
Severe gum problems.
Itching.
Impotence in men.
Unusual sensations, such as tingling or burning, in the extremities.

Symptoms in children are often different:

Most children are obese or overweight.
Increased urination is mild or even absent.
Many develop a skin problem called acanthosis, which is characterized by velvety, dark colored patches of skin.

WHAT ARE THE DIAGNOSTIC TESTS FOR TYPE ll DIABETES?

Diagnosing Diabetes

Experts now recommend that everyone over age 45 be tested regularly for diabetes. Younger adults should be tested who have the following conditions:

A weight that is 20% more than ideal body weight.
High blood pressure.
Low HDL cholesterol levels (under 35 mg/dl) and high triglyceride levels (over 250 mg/dl).
A close relative with diabetes.
A high-risk ethnic group background.
Delivered a baby weighing over nine pounds.
A history of gestational diabetes.

Some experts recommend that any child over 10 should be tested for type ll diabetes (even if they have no symptoms), if they are overweight and have at least two of the above mentioned risk factors. It should be noted that children who have symptoms of diabetes are usually diagnosed with type 1. This is of particular concern given the rise in childhood type 2 diabetes, and some centers report a misdiagnosis in 25% of cases.

Testing for Diabetes

Fasting Plasma Glucose. In order to simplify the diagnosis of diabetes, the American Diabetes Association has recommended the sole use of the fasting plasma glucose (FPG)(Fasting Plasma Glucose) test. It is a simple blood test taken after eight hours of fasting. In general results indicate the following:

FPG (Fasting Plasma Glucose) levels are considered normal up to 110 mg/dl (or 6.1 mmol/L).
Levels between 110 and 125 (6.1 to 6.9 mmol/L) are referred to as impaired fasting glucose. They are only slightly above normal but are considered to be risk factors for diabetes type ll and its complications.
Diabetes is diagnosed when FPG levels are 126 mg/dl (7.0 mmol/L) or higher on two different days.

The FPG (Fasting Plasma Glucose) test is not always reliable and there is considerable controversy about using it as the sole basis for diagnosing diabetes. Arguments against its sole use are the following:

Some experts argue that the 126 mg/dl cut-off causes many people to be diagnosed with diabetes type ll who are only at very small risk for actual complications.
On the other hand, the test may show normal results in many people who are still at risk for diabetes. For example, people who take the test in the afternoon and show normal results may have abnormal (and more accurate) levels if they are tested in the morning.
It is it not as useful as the glucose tolerance test for predicting people at high risk for diabetes, heart disease or death, nor is it as useful as the glycated hemoglobin test for identifying people with diabetes at risk for severe complications.
Some research indicates that the FPG (Fasting Plasma Glucose) is not as accurate as the glucose tolerance test for detecting diabetes in specific groups (eg, women with a history of gestational diabetes or certain Asian populations.)

At this time, even if a person has normal FPG (Fasting Plasma Glucose) levels but still has symptoms of diabetes and a family history or other risk factors, then diabetes should not be ruled out and a glucose tolerance test should also be performed.

Glucose Tolerance Test. A glucose tolerance test uses the following procedures:

It first employs an FPG (Fasting Plasma Glucose) test.
A blood test is then taken two hours later after drinking a special glucose solution.

The following results suggest different conditions:

In people without diabetes, blood sugar increases modestly after drinking the glucose beverage and decreases after two hours.
In diabetes, the initial increase is significant and the level remains high, 200 mg/dL (11.1 mmol/L) or more.
Measurements that fall between 7.8 and below 11.1 mmol/l puts a person at risk for diabetes and are referred to as impaired glucose tolerance . This condition is now strongly associated with a high risk for future diabetes and a higher than average risk for heart disease and poorer survival rates. (Studies suggest it is a much stronger predictor of diabetes than impaired fasting glucose. See Above.)

Test for Glycated Hemoglobin. Another test examines blood levels glycated hemoglobin , also known as hemoglobin A1c (HbA1c). Measuring glycated hemoglobin is not currently used for an initial diagnosis, but it may be useful for determining the severity of diabetes. Some experts think it should be used to help predict complications in people who have FPG levels between 110 and 139, which are above normal but do not indicate full-blown diabetes.

The basis for its use as a diagnostic measurement in diabetes is as follows:

Hemoglobin is a protein molecule found in red blood cells. When glucose binds to it, the hemoglobin becomes modified, a process called glycosylation.
Glycosylation affects a number of proteins, and elevated levels of glycolated hemoglobin is strongly associated with complications of diabetes.
A glycated hemoglobin level of 1% above normal range identifies diabetes in 98% of patients. Normal HbA1c levels do not necessarily rule out diabetes, but if diabetes is present and levels are normal, the risk for complications is low.

The test is not affected by food intake so it can be taken at any time. A home test has been developed that might make it easier to measure HbA1c. In general, measurements suggest the following:

Normal HbA1c levels should be below 7%.
Levels of 11% to 12% glycolated hemoglobin indicate poor control of carbohydrates. High levels are also markers for kidney trouble.
for Insulin Resistance. Investigators hope that some day a simple test for insulin resistance will be available that will be able to identify people at risk for diabetes. Some research suggests that measuring insulin and triglyceride levels during a fasting period may predict a person's sensitivity to insulin.

Screening Tests for Complications

Screening for Heart Disease. All patients should be tested for hypertension and unhealthy cholesterol and lipid levels and given an electrocardiogram. Other tests may be warranted in patients with signs of heart disease.

Screening for Kidney Damage. The earliest manifestation of kidney damage is microalbuminuria, in which tiny amounts (30 to 299 mg per day) of protein called albumin are found in the urine. About 20% of type ll patients show evidence of microalbuminuria upon diagnosis of diabetes. It should be noted, however, that only a small percentage of type ll diabetics eventually develop kidney disease. Microalbuminuria is also a marker for other complications involving blood vessel abnormalities, including heart attack and stroke.

Screening for Thyroid Abnormalities. Thyroid function tests should be administered.