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Apolipoproteins: the lipid measurement of choice?
Should the apolipoprotein B/A1 ratio become the routine lipid measurement for cardiovascular risk stratification? From a pathophysiological point of view, the Apo B/A1 ratio is more reflective of endothelial dysfunction and atherosclerosis development than the level of low-density lipoprotein (LDL) cholesterol. However, results from several small studies (200–300 events) have been conflicting—while some showed a superiority of Apo B/A1 over conventional lipid measurements, others, including a report from the Framingham heart study, did not.
Data from the INTERHEART study were used to measure cholesterol and apolipoprotein ratios for 9345 cases of myocardial infarction and 12 120 controls. The Apo B/A1 ratio had the highest population-attributable risk (54%), compared with the LDL/high-density lipoprotein (HDL) cholesterol ratio which was 37%, and total cholesterol/HDL ratio which was 32%, significantly lower than the Apo B/A1 ratio (p<0.0001). These results were consistent across all ethnic groups, both sexes and all ages.
A trend appears to be emerging against the use of the traditional LDL cholesterol measurement; a recent study of patients in the TNT (Treating to New Targets) and IDEAL (Incremental Decrease in End Points through Aggressive Lipid Lowering) trials also suggested that Apo B was more closely associated with cardiovascular outcomes than levels of LDL cholesterol. This is perhaps not totally surprising, as LDL cholesterol does not take into account potentially atherogenic intermediate-density particles. However, some have cautioned against a rapid change in terminology, arguing that the public have only just begin to grasp the importance of maintaining a low LDL cholesterol.
▸ McQueen MJ, Hawken S, Wang X, et al. For the INTERHEART Study Investigators. Lipids, lipoproteins, and apolipoproteins as risk markers of myocardial infarction in 52 countries (the INTERHEART study): a case-control study. Lancet 2008;372:224–33.
▸ Lind L. Apolipoprotein B/A1 and risk of cardiovascular disease. Lancet 2008;372:185–6.
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