NEW YORK (Reuters Health) – High levels of apolipoprotein B (apoB) and low levels of apolipoprotein A-I (apoA-I) are highly predictive of fatal myocardial infarction (MI), regardless of lipid concentrations, Scandinavian researchers report in The Lancet for December 15.
Dr. Goran Walldius from AstraZeneca, Mצlndal, Sweden, and colleagues from the Apolipoprotein-related Mortality Risk Study collected data on 175,553 men and women who were identified mostly from screening programs. Among these subjects, the researchers measured levels of total cholesterol, apoB, apoA-I, and triglycerides. They then calculated the apoB/apoA-I ratio and levels of HDL and LDL cholesterol.
During a mean follow-up of 66.8 months, 864 of 98,722 men in the study had fatal MIs. During a mean follow-up of 64.4 months, 359 of 76,831 women had fatal MIs, the researchers report.
Multivariate analysis revealed that apoB concentrations and the apoB/apoA-I ratio positively correlated with an increased risk of fatal MI. In addition, apoB concentration was a stronger predictor of fatal MI risk than was LDL cholesterol among men and women. High levels of apoA-I were also identified as protective against fatal MI, Dr. Walldius' team found.
"Although LDL-cholesterol and HDL-cholesterol are known risk factors, we suggest that apoB, apoB/apoA-I, and apoA-I should also be regarded as highly predictive in evaluation of cardiac risk," Dr. Walldius and colleagues write.
"Although increased throughout the range of values of LDL-cholesterol, apoB and apoA-I might be of greatest value in diagnosis and treatment in men and women who have common lipid abnormalities, but have normal or low concentrations of LDL-cholesterol," they add.
"Before apoB and apoA-I can be used in routine clinical practice, assay methods need to be standardised and threshold and target values for diagnosis and treatment need to be agreed," Drs. Sathanur R. Srinivasan and Gerald S. Berenson from the Tulane University Health Sciences Center, New Orleans, comment in a journal editorial.
"Quality control and assurance for apolipoprotein measurements, unlike those for measurements of cholesterol and triglycerides, are not applied in most commercial laboratories. This lack must be rectified before any specific clinical recommendations can be made." Drs. Srinivasan and Berenson stress.