Miller recommends that patients taking 400 IU of vitamin E per day or more, stop. He says the small amount of E in a multivitamin is probably fine, but stresses that no vitamin regimen is a substitute for a good diet, regular exercise and adequate sleep.

The test measures gamma-glutamyl transferase (GGT) - an enzyme produced primarily by the liver and catalyzes glutathione, the main antioxidant in the body. The enzyme is elevated in some forms of liver disease, so physicians use GGT levels to detect liver damage and alcohol abuse.

"People with high GGT had more than a 1.5-fold risk of dying from cardiovascular diseases in comparison to people with normal low levels of GGT," said senior author Hanno Ulmer, PhD, associate professor of medical statistics at the Innsbruck Medical University in Austria. "For people under 60 years of age, this risk is even higher, amounting to more than two-fold."

GGT proved a strong predictor of cardiovascular death, third behind smoking and hypertension but ahead of high levels of blood sugar, cholesterol and triglycerides. Ulmer cited two mechanisms that might explain why GGT can indicate cardiovascular disease. The first, originally proposed by the Italian researchers, is that high GGT shows the presence of atherosclerosis. The second is that it's related to the ill effects of heavy drinking on blood vessels.

Participants with pre-diabetes and retinopathy typically had a small number of microaneurysms in the eye characteristic of early, mild retinopathy that is not yet linked to vision loss. Those who had developed diabetes in the previous 1 to 5 years had slightly more severe retinopathy. Higher average blood glucose levels and higher blood pressure were associated with the risk of developing retinopathy in the new-onset diabetic patients, similar to previous findings in people with longstanding diabetes who develop retinopathy.

Pre-diabetes is a condition in which blood glucose levels are higher than normal but not high enough for a diagnosis of diabetes. The condition is sometimes called "impaired fasting glucose (IFG)" or "impaired glucose tolerance (IGT)," depending on the test used to diagnose it. People with pre-diabetes have an increased risk of developing type 2 diabetes, heart disease, and stroke. Diabetic retinopathy, which begins with changes in the small vessels in the back of the eye, often leads to loss of vision. Regular eye examinations to diagnose retinopathy are recommended for patients with diabetes because treatment with laser photocoagulation can often prevent blindness in more advanced cases. Diabetic retinopathy is still the most common cause of blindness in adults.

The test, called QuantiFERON-TB-Gold, has been approved by the Food and Drug Administration. Unlike the skin test, the interferon-gamma test requires only one visit by the patient, and its results do not rely upon the subjective interpretation of a health worker. The blood test, however, requires special lab facilities, making it more expensive than the skin test, which in turn involves more personnel time because it requires health care workers to deal with a patient twice.