Screening for heart disease by measuring levels of C-reactive protein does not provide enough useful information to make the highly touted screening test worthwhile, a new study concludes.
In fact, people with high levels of CRP -- a protein released by the liver that points to inflammation of blood vessels -- invariably are either smokers, obese, have high blood pressure or elevated cholesterol levels, so the additional test is redundant, said Michael Miller, director of preventive cardiology at the University of Maryland Medical Center in Baltimore.
"We believe that high C-reactive protein is truly related to the company it keeps," he said.
The research, published in today's edition of the Archives of Internal Medicine, found that one in four people tested had elevated CRP.
But three-quarters of the 15,000 participants whose records were analyzed had traditional risk factors for heart disease.
"If you exercise, don't smoke, have normal levels of blood pressure, cholesterol and glucose, and are not overweight, the likelihood of a high CRP is only one in 2,000," Dr. Miller said.
If anything, the CRP blood test provides a false sense of security to those at high risk of heart attack but whose livers are not producing the protein, the researcher said.
Overall, 25.7 per cent of people in the study had elevated CRP, including 8.7 per cent who had no other risk factors.
The analysis found a high CRP level in 78 per cent of men and 67 per cent of women who had at least one other risk factor for cardiovascular disease.
Dr. Miller said the money spent on CRP testing would be better used on programs to help people quit smoking and lose weight.
The CRP test became popular in the early 1990s, when it was believed that only half of heart attacks could be explained by traditional risk factors such as poor nutrition, a sedentary lifestyle, stress and the changes in blood pressure and cholesterol they produce.
But, Dr. Miller said, that "turned out to be one of the greatest myths of cardiovascular disease" and, in fact, more than 90 per cent of heart attacks could be attributed to traditional risk factors.
Many researchers have cautioned that there is no evidence that CRP causes heart disease. Others argue that CRP is as important a measure as cholesterol.
Both high cholesterol and high CRP are treated with heart drugs called statins.
While there is good evidence that this is beneficial for patients with a history of heart disease, the jury is still out on whether lowering CRP and/or cholesterol is beneficial for healthy people.
What the new research suggests is that CRP is, at best, a marker, in the same way that grey hair is a marker of aging.
Regardless, the best way to lower CRP -- and blood pressure and cholesterol for that matter -- is to lose weight, be active, and not smoke.
"Let's work more intensively to reduce the known culprits," Dr. Miller said.
Cardiovascular disease is the leading cause of death in Canada. According to Statistics Canada, 74,600 people died of heart disease in 2002, the most recent year for which data are available.