The ratio of two forms of apolipoprotein in the blood is substantially better at predicting heart attack risk than the standard method of using cholesterol ratios, according to the multi-national INTERHEART study published in July 19 issue of the Lancet.
Apolipoproteins are fat binding-proteins that form part of lipoproteins, sub-microscopic spherical particles that transport dietary lipids through the bloodstream from the intestine to the liver; cholesterol is a type of lipid found in the blood of all animals.
Matthew McQueen, MBChB, from the Population Health Research Institute and McMaster University in Hamilton, Ontario, and colleagues studied acute MI in 12,461 cases and 14,637 age-matched and sex-matched controls in 52 countries. The authors noted that non-fasting blood samples were available in 9,345 cases and 12,120 controls.
The researchers measured concentrations of blood fats, lipoproteins and apolipoproteins, and calculated cholesterol and apolipoprotein ratios, along with the risk associated with acute MI.
The investigators found that the apolipoprotein B100 (ApoB)/apolipoprotein A1 (Apo A1) ratio accounted for 54 percent of the risk of MI. By contrast, the ratio of bad to good cholesterol accounted for 37 percent of the risk, whereas the ratio of total cholesterol to good cholesterol accounted for 32 percent. The ApoB to Apo A1 ratio was thus almost twice as powerful a predictor of this risk, according to the authors.
McQueen and colleagues wrote that the “non-fasting ApoB/ApoA1 ratio was superior to any of the cholesterol ratios for estimation of the risk of acute heart attack in all ethnic groups, in both sexes, and at all ages, and it should be introduced into worldwide clinical practice.”
In an accompanying comment, Lars Lind, MD, from the University Hospital in Uppsala, Sweden, wrote that apolipoproteins can be measured in a standardized and automatic manner at a similar cost to conventional cholesterol analysis, and concluded that substituting cholesterol tests with those analyzing apolipoprotein ratios would be a demanding but not impossible task.
Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario, the International Clinical Epidemiology Network (INCLEN) funded the study. The researchers also received unrestricted grants from pharmaceutical companies contributions from AstraZeneca, Novartis, Aventis, Abbott, Bristol Myers Squibb, King Pharma and Sanofi-Synthelabo.