Diabetes: Type 2

Description

Alternative Names

Screening Tests

There are no clear-cut guidelines for when to screen for diabetes. Some experts recommend that everyone over age 45 be tested regularly for diabetes, although others do not feel this necessary in people without symptoms or risk factors. In fact, early screening could identify some people with impaired glucose levels that would eventually normalize. Such people might be treated unnecessarily with medications that pose a risk for hypoglycemia.

Still, given the risk for serious complications with diabetes and the potential value of early treatments, most experts recommend that all adults over 45 be screened and that younger adults be screened if they have one or more of the following conditions:

• A weight that is 20% more than ideal body weight.
• Risk factors for heart disease (e.g., high blood pressure, unhealthy cholesterol levels and especially if individuals have low HDL cholesterol and high triglyceride levels).
• A close relative with diabetes.
• A high-risk ethnic group background.
• In women, having delivered a baby weighing over nine pounds or having a history of gestational diabetes.

Some experts recommend that any child over 10 should be tested for type 2 diabetes (even if they have no symptoms), if they are overweight and have at least two of the above mentioned risk factors. Determining the risks and benefits of such an approach is of particular importance, given the rise in childhood type 2 diabetes. Type 2 diabetes is still uncommon in children and adolescents.

Testing for Diabetes

Fasting Plasma Glucose. The fasting plasma glucose (FPG) test is the standard test for diabetes. It is a simple blood test taken after eight hours of fasting. In general, results indicate the following:

• FPG 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 type 2 diabetes 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 test is not always reliable, so a repeat test is recommended if the initial test suggests the presence of diabetes, or if the test is normal in people who have symptoms or risk factors for diabetes. For example, people who take the test in the afternoon and show normal results may actually have abnormal levels that would be revealed if they are tested in the morning.

Glucose Tolerance Test. The glucose tolerance test is more complex than the FPG and may over-diagnose diabetes in people who do not have it. It is, then, not used as often anymore. Some experts recommend it follow-up after FPG, if the latter test results are normal but the patient has symptoms or risk factors of diabetes. The glucose tolerance test may be more accurate than the FPG in certain groups (e.g., women with a history of gestational diabetes or certain Asian populations). The test uses the following procedures:

• It first employs an FPG 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 put 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.)

Test for Glycated Hemoglobin. Tests for blood levels of glycated hemoglobin, also known as hemoglobin A1c (HbA1c) are not currently used for an initial diagnosis, but they are 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.

Testing 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. The presence of insulin resistance may also be a predictor of heart disease, independent of the presence of 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 with diabetes 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.

The electrocardiogram (ECG, EKG) is used extensively in the diagnosis of heart disease, from congenital heart disease in infants to myocardial infarction and myocarditis in adults. Several different types of electrocardiogram exist.

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 2 patients show evidence of microalbuminuria upon diagnosis of diabetes. It should be noted, however, that only a small percentage of type 2 diabetics eventually develop kidney disease. Microalbuminuria typically shows up in type 2 diabetics who have high blood pressure.

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