Measurement of lipid components called apolipoproteins could be a better indicator of heart-attack risk than conventional cholesterol assessment, conclude authors of a study in this week’s issue of THE LANCET.
Hypercholesterolaemia, especially high concentrations of LDL-cholesterol, is one of the strongest risk factors for atherosclerotic cardiovascular disease. Recent studies have suggested that apolipoprotein B (apoB) and apolipoprotein A-I (apoA-I) might be better predictors of acute heart attack (myocardial infarction) than total cholesterol and LDL-cholesterol. Goran Walldius from AstraZeneca and the Karolinska Institute, Stockholm, Sweden, and colleagues investigated whether apoB and apoA-I were predictors of heart-attack risk. They also aimed to establish whether apoB and apoA-I could add further information about the risk of fatal heart attack to that obtained with total cholesterol, triglycerides, and LDL-cholesterol.
Around 175,000 Swedish people were studied, mainly from screening programmes. Concentrations of apoB, apoA-I, total cholesterol, and triglycerides were measured; the ratio for apoB/apoA-I and concentrations of LDL-cholesterol and HDL-cholesterol were calculated.
Average follow-up occurred at five and a half years after initial blood testing. 864 men and 359 women died from heart attack during the follow-up period. Total cholesterol, triglycerides, apoB and a high apoB/apoA-I ratio were strongly and positively related to increased risk of fatal heart attack in both men and women. Higher concentrations of ApoA-I had a protective effect; apoB was a stronger predictor of risk than LDL-cholesterol in both sexes.
Goran Walldius comments: “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. 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.”
In an accompanying Commentary (p 2012), Gerald Berenson from Tulan University Health Sciences Centre, New Orleans, USA, cautions: “Before apo B and apo A-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…”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.”
The Lancet