Apoliproteins are essential to the transport of blood lipids through the bloodstream and to the uptake of blood lipids into body cells. Apo B-100 is manufactured in the liver. It combines with very low-density lipoproteins (VLDL) to carry triglycerides and LDL cholesterol in the bloodstream. By measuring levels of Apo B, it is possible to measure the exact number of LDL particles.
Some researchers believe that measurements of Apo B may be better than LDL measurements when it comes to predicting the risk of heart disease. This is because levels of Apo B can be measured directly, while LDL cholesterol levels are often calculated indirectly from levels of total cholesterol. These indirect calculations tend to be less accurate as triglyceride levels increase. But experts believe that research evidence is not sufficient to support the superiority of Apo B over LDL cholesterol measures. Therefore, federal government guidelines do not yet recommend the Apo B measure as a factor in risk assessment. This may change as new tests continue to be developed and are more accurate and standardized.
Most LDL levels are calculated indirectly, by measuring the total weight of all LDL cholesterol present rather than by calculating the actual number of LDL particles. Tests that measure Apo B measure the exact number of LDL particles, providing insight into whether the LDL cholesterol is composed of the large, fluffy type or the small, dense type that is worse for health.
Research on Apo B
In October 2003, results from the Insulin Resistance Atherosclerosis Study were published in Circulation: Journal of the American Heart Association. Researchers used a number of tests to determine whether people should be put on therapy. Interestingly, researchers found that 19 percent of subjects would have received a different treatment recommendation if they had been tested for Apo B levels rather than for LDL levels. Investigators who conducted the study confirmed that LDL is still an important marker for heart disease risk. However, researchers believe that testing for Apo B levels provides even more valuable information. The test is inexpensive and does not require fasting.
Alice Lichtenstein, a spokesperson for the American Heart Association, said, “This is an important observation and needs to be considered carefully in light of prior data to determine whether current guidelines should be modified to recommend routinely measuring Apo B levels in high risk individuals.” National government guidelines in Canada recommend use of the Apo B test. Watch for potential changes in government guidelines in the United States.