Standard lipid tests may demonstrate a normal LDL and total cholesterol level in patients with a risk of atherosclerotic disease. Moreover, patients with significant reduction in LDL cholesterol following lipid lowering therapy may still develop coronary heart disease. Thus, standard lipid testing, which measures total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides, is not sufficient to predict the overall risk for heart attack and strokes.
Advanced lipid testing provides information on additional risk factors to help evaluate the cardiovascular risk more effectively and monitor the effects of lipid lowering therapy. Two of the most common risk factors measured in advanced lipid testing include apolipoprotein B (ApoB) and LDL-particle number (LDL-P).
ApoB: It measures the total bad cholesterol or atherogenic lipoproteins in blood, which has the potential to cause cardiovascular disease (CVD). The components of bad cholesterol include very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), large buoyant-low density lipoprotein (LDL) and small dense LDL. One ApoB molecule is present in each of these bad cholesterol components. Therefore, the total number of ApoB indicates the total quantity of bad cholesterol. High levels of ApoB indicate an increased risk of CVD, even with normal LDL cholesterol levels.
LDL particles: High LDL cholesterol level increases the risk of heart disease. LDL can occur as large buoyant LDL particle, or as small dense LDL particles with less cholesterol per particle. Thus, even for normal levels of LDL, there can be large numbers of small dense LDL particles per liter of plasma. Moreover, these small dense LDL particles are more atherogenic than large buoyant LDL particles and more easily invade the walls of the arteries, increasing the risk of plaque formation.
Advanced lipid testing evaluates the actual number of LDL particles that carry LDL cholesterol per liter of plasma and the size of these particles as well. sdLDL stands for small dense LDL and high levels of sdLDL indicate increased risk of CVD. The presence of large numbers of sdLDL particles may be secondary to insulin resistance, which may indicate a risk of developing diabetes.
Advanced lipid testing may also include Lipoprotein (a) or Lp (a) and ApoA1.
Lipoprotein (a): Levels of lipoprotein (a) are genetically determined, and are not affected by changes in lifestyle or drugs. High levels of this lipoprotein indicate increased risk of CVD and cerebrovascular disease. Lipoprotein (a) estimation is recommended in individuals with a strong family history of premature CVD.
ApoA1: This measures the total number of good cholesterol in blood. High levels of ApoA1 indicate a decreased risk of CVD. This test may be ordered along with ApoB to determine the ratio of ApoB/ApoA1, which indicates the balance between potentially atherogenic and atheroprotective cholesterol, which is a better predictor of risk than either parameter alone.
ApoB, ApoA1, lipo (a) and LDL-particle are all simple blood tests. Advanced lipid testing may be recommended at the initial visit and also at regular intervals during treatment. Sometimes, it is recommended, only after successful achievement of the LDL cholesterol and non-HDL cholesterol goals, to check the effectiveness of the lipid-lowering therapy (a combination of healthy lifestyle and cholesterol lowering medication).