Results of the study have important implications for deciding whether cholesterol-lowering statin medication should be prescribed for people who have heart disease risk factors but normal levels of LDL, the so-called "bad" cholesterol. An estimated 6 million American adults fall into that gray-zone category.
The goal of the study, which followed 2,083 people for six years, was to further refine who was at higher risk and, therefore, might benefit from taking statin medications.
Michael J. Blaha, M.D. M.P.H, a cardiology fellow at the Johns Hopkins University School of Medicine and the Johns Hopkins Heart and Vascular Institute, who is the lead author of the study, said, "This was a direct comparison to see which patients with a normal LDL level of less than 130 mg/dL would have the greater risk of having a heart attack or stroke -- those with evidence of calcium in coronary arteries, as determined on a cardiac CT test, or those with high levels of C-reactive protein, which is measured in blood and is an indicator of inflammation somewhere in the body."
Blaha and colleagues found that 95 percent of the heart attacks, strokes or heart-related deaths in the study population occurred in people with some measurable calcium in their heart arteries. Meanwhile, 13.4 percent of those with the highest levels of coronary calcium (with scores greater than 100 on a calcium scoring test) had a heart attack or stroke during the study, whereas only 2 percent of those with high C-reactive protein in their blood, but no calcium buildup, had a heart attack or stroke.
In their study, the researchers determined that high levels of C-reactive protein in the blood, a score at or above 2 milligrams per liter, offered little predictive value after accounting for such risk factors as age, gender, ethnicity, hypertension, obesity, diabetes, smoking and a family history of heart disease.
Dr. Blaha explained that, "A calcium test directly looks for the disease we propose to treat with statins. Without measurable amounts of calcium, which indicates atherosclerosis, you are likely to be at very low risk in the short-term."
"While not everyone needs a calcium scoring test," Dr. Blaha said, "we believe looking for calcification in coronary vessels in certain patients makes sense in order to predict who may benefit from statin therapy because the test gets right to the heart of the disease we want to treat."
The Lancet, published online August 23, 2011