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Diabetes - type 2 - Diagnosis

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of type 2 diabetes.

Alternative Names

Type 2 diabetes; Maturity onset diabetes; Noninsulin-dependent diabetes

Diagnosis:

Healthy adults age 45 and older should get tested for diabetes every 3 years. Patients who are younger than age 45 and who have certain risk factors should ask their doctors about testing. These risk factors include:

A weight that is 20% more than ideal body weight
Sedentary lifestyle
High blood pressure (greater than 140/90) or unhealthy cholesterol levels -- especially for patients with low HDL ("good") cholesterol and high triglyceride levels
History of heart disease, stroke, or peripheral artery disease
A close relative (parent, sibling) with diabetes
A high-risk ethnic group background (African-American, Latino, Native American, Asian American, Pacific Islander)
Having delivered a baby weighing over 9 pounds or having a history of gestational diabetes (in women)
Polycystic ovary disease (in women)

Children age 10 and older should be tested for type 2 diabetes (even if they have no symptoms) every 3 years if they are overweight and have at least two risk factors.

Testing for Diabetes and Pre-Diabetes

Pre-diabetes precedes the onset of type 2 diabetes. People who have pre-diabetes have fasting blood glucose levels that are higher than normal, but not yet high enough to be classified as diabetes. (Pre-diabetes used to be referred to as “impaired glucose tolerance.”) Pre-diabetes greatly increases the risk for diabetes.

The fasting plasma glucose (FPG) test, alone or in combination with the oral glucose tolerance test (OGGT) can help diagnose pre-diabetes and diabetes.

Fasting Plasma Glucose. The fasting plasma glucose (FPG) test is the standard test for diabetes. It is a simple blood test taken after 8 hours of fasting. FPG levels indicate:

Normal. 100 mg/dL (or 5.5 mmol/L) or below.
Pre-Diabetes. Between 100 - 125 mg/dL (5.5 - 7.0 mmol/L).
Diabetes.126 mg/dL (7.0 mmol/L) or higher.

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.

Glucose Tolerance Test. The oral glucose tolerance test (OGTT) is more complex than the FPG and may over-diagnose diabetes in people who do not have it. Some doctors recommend it as a follow-up after FPG, if the latter test results are normal but the patient has symptoms or risk factors of diabetes. The test uses the following procedures:

The patient first has an FPG test.
The patient has a blood test 2 hours later, after drinking a special glucose solution.

OGGT levels indicate:

Normal. 140 mg/dL or below.
Pre-Diabetes.Between 140 - 199 mg/dL
Diabetes.200 mg/dL or higher.

The patient cannot eat for at least 8 hours prior to the FPG and OGTT tests.

Glycosylated Hemoglobin Test. This test examines blood levels of glycosylated hemoglobin, also known as hemoglobin A1c (HbA1c). The test is not affected by recent food intake so it can be taken at any time.

The results of a blood glucose test tell the patient and doctor how well the diabetes is controlled for only the day of the test. An elevated hemoglobin A1c level tells the doctor and the patient how well controlled the patients diabetes has been over the last 3 months or so.

Measuring glycosylated hemoglobin is generally not used for making an initial diagnosis of diabetes, since a normal level does not rule out diabetes. In people without diabetes, a normal HbA1c range is between 4 - 6%. Elevated levels of glycosylated hemoglobin are strongly associated with most if not all of the complications of diabetes.

In general, most patients with diabetes should aim for HbA1c levels below 7%. Your doctor may adjust this goal depending on your individual health profile.

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 needed in patients with signs of heart disease.

The electrocardiogram (ECG or 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 - 300 mg per day) of protein called albumin are found in the urine. Microalbuminuria typically shows up in patients with type 2 diabetes who have high blood pressure.

The American Diabetes Association recommends that people with diabetes receive an annual microalbuminuria urine test. Patients should also have their blood creatinine tested at least once a year. Creatinine is a waste product that is removed from the blood by the kidneys. High levels of creatinine may indicate kidney damage. A doctor uses the results from a creatinine blood test to calculate the glomerular filtration rate (GFR). The GFR is an indicator of kidney function; it estimates how well the kidneys are cleansing the blood.

Screening for Retinopathy. The American Diabetes Association recommends that patients with type 2 diabetes get an initial comprehensive eye exam by an ophthalmologist or optometrist shortly after they are diagnosed with diabetes, and once a year thereafter. (People at low risk may need follow-up exams only every 2 - 3 years.) The eye exam should include dilation to check for signs of retinal disease (retinopathy).

Screening for Neuropathy. All patients should be screened for nerve damage (neuropathy), including a comprehensive foot exam. Patients who lose sensation in their feet should have a foot exam every 3 - 6 months to check for ulcers or infections.

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

Resources

www.diabetes.org -- American Diabetes Association
www.niddk.nih.gov -- National Institute of Diabetes and Digestive and Kidney Diseases
www.americanheart.org -- American Heart Association
www.kidney.org -- National Kidney Foundation
www.nei.nih.gov -- National Eye Institute
www.medicalert.org -- Medic Alert
www.eatright.org -- American Dietetic Association

References

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Reviewed last on: 5/5/2009
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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