Calcium buildup in the coronary arteries of chronic kidney disease patients may be a strong indicator of heart disease risk, according to a new study in the Journal of the American Society of Nephrology (JASN). Researchers at the Johns Hopkins Bloomberg School of Public Health assert that coronary calcium outperforms two other commonly used measures of subclinical atherosclerosis in predicting the risk of heart disease among individuals with kidney disease.

Approximately 50 percent of all patients with chronic kidney disease (CKD) die from cardiovascular disease, but some previous studies concluded that conventional risk factors for predicting heart disease -- such as blood pressure and lipid levels -- were not as useful in CKD patients.

Kunihiro Matsushita, MD, PhD, an assistant scientist in the Bloomberg School's Department of Epidemiology, and his colleagues, decided to investigate whether other tests might be more helpful in predicting cardiovascular disease in those with CKD. They compared three measures of atherosclerosis -- calcium levels within blood vessel walls, the thickness of the carotid artery walls, and narrowing of arteries in the legs.

Although the amount of coronary calcium is a potent predictor of heart disease in the general population, Matsushita says it wasn't clear whether it would be as useful in people with CKD. The kidneys help regulate the body's calcium levels, and individuals with CKD often have an altered calcium metabolism, which researchers were concerned could influence the usefulness of calcium in the coronary artery walls as a predictor of heart disease. Coronary calcium levels are determined by computer tomography (CT).

The study included 6,553 adults in the Multi-Ethnic Study of Atherosclerosis between the ages of 45 and 84 years who did not have prior cardiovascular disease; 1,284 of them had CKD. After eight years, 650 cardiovascular events (coronary heart disease, stroke, heart failure, and peripheral artery disease) occurred, with 236 of the events occurring in those with CKD. Looking back, the researchers determined that calcium buildup was more accurate in correctly determining CKD patients' risk of cardiovascular disease (especially coronary heart disease and heart failure), than measures of thickening of the carotid artery walls or narrowing of arteries in the legs.

"Our research is important since it assures the usefulness of coronary artery calcium for better cardiovascular disease prediction in persons with CKD, a population at high risk for cardiovascular disease but with potential caveats for the use of traditional risk factors," Matsushita says.