Diagnosis:

Testing for Glucose Abnormalities

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

FPG levels indicate:

• Normal. U100 mg/dL (or 5.5 mmol/L) or below.
• Pre-Diabetes. (a risk factor for type 2 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 tests are normal in people who have symptoms or risk factors for diabetes. Widespread screening of patients to identify those at higher risk for diabetes type 1 is not recommended.

Glucose Tolerance Test. The oral glucose tolerance test (OGTT) is more complex than the FPG and may overdiagnose 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:

• It first uses an FPG test.
• A blood test is then taken 2 hours later after drinking a special glucose solution.

OGTT levels indicate:

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

Patients who have the FPG and OGTT tests must not eat for at least 8 hours prior to the test.

The oral glucose tolerance test is used to diagnose diabetes. The first portion of the test involves drinking a special glucose solution. Blood is then taken several hours later to test for the level of glucose in the blood. Patients with diabetes will have higher than normal levels of glucose in their blood.

Test for Glycosylated Hemoglobin (Hemoglobin A1c). 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.
• Once a blood sugar molecule sticks to a hemoglobin molecule, which are found in every red blood cell, it never lets go (a process called glycation). If a patient with diabetes has elevated blood glucose on many days, more blood glucose molecules will stick to the hemoglobin molecule. If that happens, the hemoglobin A1c level will be higher.
• Therefore, 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 not generally 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 adults with diabetes should aim for HbA1c levels below 7%. Higher levels indicate poor blood glucose control.

Goal HbA1c levels for children are:

• Between 7.5 - 8.5% for children under age 6 years
• Less than 8% for children age 6 - 12 years
• Less than 7.5% for children age 13 - 19 years

Schedule for HbA1c Monitoring:

• Every 6 months if diabetes is well controlled
• Every 3 months if not well controlled

Autoantibody Tests

Type 1 diabetes is characterized by the presence of a variety of antibodies that attack the islet cells. These antibodies are referred to as autoantibodies because they attack the body's own cells -- not a foreign invader. Blood tests for these autoantibodies can help differentiate between type 1 and type 2 diabetes.

Screening Tests for Complications

Screening Tests for Heart Disease. All patients with diabetes should be tested for:

• Blood pressure. Your doctor should check your blood pressure at every visit. Blood pressure goals should be 130/80 mm Hg or lower.
• Lipid levels, including cholesterol. People with diabetes should aim for LDL levels below 100 mg/dL, HDL levels over 40 mg/dL, and triglyceride levels below 150 mg/dL. Testing should be performed yearly and perhaps every other year for patients with good lipid control and no evidence of heart disease.
• Cardiac exercise testing should be considered for adult patients with any symptoms or electrocardiogram findings, or before starting an exercise program.

Screening Tests for Kidney Damage. The earliest manifestation of kidney disease is microalbuminuria, in which tiny amounts (30 - 300 mg per day) of protein called albumin are found in the urine. Microalbuminuria is also a marker for other complications involving blood vessel abnormalities, including heart attack and stroke.

People with diabetes should have 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 cleaning the blood.

Screening for Retinopathy. The American Diabetes Association recommends that patients with type 1 diabetes have an annual comprehensive eye exam, with dilation, to check for signs of retina disease (retinopathy). Patients at low risk may need exams only every 2 - 3 years.

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.