Report on protein test to predict heart attack sounds cautious note

The Mass. General research does not directly contradict a landmark study from Brigham and Women’s Hospital last year - which was highly supportive of testing for C-reactive protein - but sounds a more cautious note on expanding its use. It is the latest study in one of cardiology’s hottest areas, which has pitted specialists in a decade-long back and forth over the value of screening patients with the test.

A separate genetics study, reported in the same issue of The Journal of the American Medical Association, suggests that the protein itself is not the cause of heart disease but may merely be an indicator of its existence.

C-reactive protein is a measurement of inflammation in the arteries designed to predict whether patients are prone to dangerous blood clots. The simple blood test was pioneered by physicians at Brigham, and while some cardiologists and internists screen certain patients to help determine their risk level, the test is controversial because of the conflicting research on its predictive value.

For example, in a 2004 study, European researchers said C-reactive protein was only a moderate predictor of risk.

Doctors - and patients - are intensely interested in C-reactive protein because of its potential to predict cardiovascular disease among older adults who don’t have the traditional warning signs of dangerously clogged arteries, such as previous episodes of chest pain, high cholesterol, high blood pressure, or a history of smoking. Every year, nearly 900,000 Americans die from cardiovascular disease, the nation’s leading killer. But half of people who suffer heart attacks or strokes have no warning signs.

Researchers at Mass. General and Lund University in Sweden studied more than 5,000 residents of Sweden, from 1991 through 2006, reviewing medical records that included incidents of heart attacks and stroke. Researchers obtained blood samples and tested for C-reactive protein and five other potential indicators for cardiovascular disease. They then used a complicated statistical analysis to determine whether knowing the patients’ level of CRP and other biomarkers would have changed how doctors treated them.

They determined the new information would have changed patients’ risk classification in only 8 percent of cases and would have changed the therapy recommended under current guidelines in less than 1 percent of cases.

“The evidence does not support routine screening of people for these biomarkers,’’ said Dr. Thomas Wang of the MGH Heart Center and the senior author. “It might be useful for some people. If a physician is on the fence about whether to treat a patient, this little bit of information might help.’’

The two articles come eight months after Brigham researchers presented their findings on a major C-reactive protein study involving 18,000 people in 26 countries. They prescribed a cholesterol-lowering statin drug to participants with high CRP results but healthy cholesterol readings. The results were overwhelmingly positive, with heart attacks and strokes cut by half among participants who received the pill.

The C-reactive protein test was pioneered by Brigham physicians, and both the hospital and Dr. Paul Ridker, who presided over the research, stand to profit from royalties if its use is widely expanded. The test typically costs less than $100.

Ridker was not available for comment on the Mass. General study yesterday. But he did issue a statement on the genetics study, led by researchers in London, saying that whether CRP causes heart disease - or is just a marker for it - shouldn’t change how doctors treat patients.

Several other specialists agreed on that point. But they offered no uniform opinion on the impact of the Mass. General study on current practice. Now, the use of C-reactive protein testing varies widely from doctor to doctor, although many physicians use it for patients on the borderline of needing treatment.