Have new lab tests improved the prediction of heart attacks?

News item questioning new tests for predicting heart attacks

It has been known for many years that the risk of heart attack and stroke is increased in individuals with low fasting plasma levels of high density lipoproteins (‘good’ cholesterol) and raised levels of low density lipoproteins (‘bad’ cholesterol) and triglycerides. Risk is increased by diabetes, raised blood pressure, a family history of heart disease, increasing age, obesity (particularly a ‘pot belly’), smoking and lack of exercise. However, these factors do not fully explain the risk. Over the last few years interest has increased in new lab tests for markers that have shown an association with cardiac risk in the community.

Framingham Heart Study research workers thought that the measurement of several markers simultaneously might improve the evaluation of risk. They examined 3209 community-based participants in the Framingham Offspring Study between 1995 and 1998, taking and storing fasting samples for laboratory analysis. Among the 10 markers that were measured were high-sensitivity C-reactive protein (CRP), brain-type natriuretic peptide (BNP), aldosterone and renin, fibrinogen and D-dimer, homocysteine, and in some but not all participants urine protein to creatinine ratio.

The results of their study were published in the New England Journal of Medicine of 21 December 2006. During the 10 years of follow-up (median 7.4 years) 6% of the participants died and 6% had a major cardiovascular event (heart attack, prolonged angina, heart failure or stroke). Taken together the 10 markers showed associations with death and cardiovascular events. Five individual markers - CRP, BNP, renin, homocysteine and urine protein – contributed to a model for predicting death, and two – BNP and urine protein – helped in a model to predict cardiovascular events. However, when conventional risk factors were added in, the improvement made by the markers in the accuracy of assessments in individuals was so small as to be negligible.

Dr. Richard A. Stein, Director of Preventive Cardiology at Beth Israel Medical Center, New York commented “This really supports the value of focusing on risk-factor reduction, not looking for a magic blood test”.

Source: Lab Tests Online UK



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