A painless three-minute test to measure cholesterol in the skin may offer a simple new way to assess a person's risk of developing heart disease, according to a study presented today at the American Heart Association's Scientific Sessions 2000.
Unlike the test for serum cholesterol, which involves extracting blood with a needle, the non-invasive skin test consists of placing a few drops of fluid in the fleshy area of the palm near the base of the thumb and measuring the resulting color change with a special meter. The test fluid is then simply washed off with water. Serum cholesterol tests measure cholesterol-carrying particles in the blood, HDL, the "good" cholesterol and LDL, the "bad" cholesterol. The skin test measures only cholesterol on the outer layer of the skin.
Each of the 381 individuals receiving the skin test subsequently underwent a test that measures blockages in the blood vessels, called coronary catheterization. The test found that those with the highest levels of skin cholesterol also had the greatest number of diseased arteries.
In the initial series, 233 individuals had the cholesterol in their skin assessed. A second series of individuals were tested with an alternate testing kit, which was developed to be more sensitive. The data reported today combines results from the 233 individuals in the first series and the second 148 individuals.
"We found that patients with the highest skin cholesterol levels have up to a 37 percent greater risk of coronary disease than those with the lowest levels," says Dennis L. Sprecher, M.D., head of preventive cardiology and rehabilitation at the Cleveland Clinic Foundation. This relationship remained significant after adjusting for age, gender and serum cholesterol.
The cost of the skin test hasn't been fully established, but it will be comparable to - and possibly less than - the cost of a blood test for serum cholesterol, Sprecher says.
If the skin test is adopted for widespread use, he adds, it could lead to the development of a home testing kit, which could be used in much the same way as home urine-testing kits are now used by many diabetic patients.
"There is no risk or discomfort involved in the use of this technique, but there are some small technical details that need to be worked out," Sprecher says. "The application strategy, for example, needs to be made absolutely user-friendly, so that the test can be administered uniformly by either consumers or health care professionals."
Further research is needed to corroborate the results of the Cleveland study before the skin test is made available to the general public. "Otherwise, we think this simple, inexpensive test has enormous potential for the medical community," he says.
The ability of skin cholesterol to predict heart disease is similar to that of blood cholesterol. However, for reasons that are not yet clear, the level of cholesterol in the skin seems to have almost no correlation with the level of cholesterol in the bloodstream, Sprecher says.
"If the serum cholesterol is extremely high, there appears to be some mild relationship, but the same person can have high serum cholesterol values and low skin values," he notes. "This may mean that, in certain individuals, the cholesterol from lipoproteins in the blood doesn't easily enter the skin tissue so the skin levels would be low."
"On the other hand," he says, "a high skin cholesterol may actually be worse than having a high blood cholesterol, because it might mean that a person has a greater susceptibility to cholesterol collecting in the walls of the blood vessels, not just traveling in the bloodstream. It may have a more direct relationship,"
More research is needed to determine if the skin test will replace blood testing or if the two may complement each other, says Sprecher.
Co-authors of the study include Michael J. Evelegh, Ph.D.; Brent Norton, M.D.; and Gregory L. Pearce, M.S.