How, when, and why to use apolipoprotein B in clinical practice.

The evidence is now clear that plasma apolipoprotein (apo) B is a better index of the risk of coronary artery disease (CAD) than total or low-density lipoprotein (LDL) cholesterol. Moreover, the evidence is also clear that clinical risk of apo B is determined not only by LDL particle number but also by whether small, dense LDL particles are present. The objective of this article, therefore, is to demonstrate how, when, and why apo B should be used in clinical practice. First, the evidence that apo B is superior to LDL cholesterol as an index of the risk of CAD and as a guide to the adequacy of statin therapy is briefly reviewed. Next, the biological bases for this superiority in identifying risk are outlined. Clinical scenarios are then outlined demonstrating the value of measuring apo B in hypertriglyceridemic, hypercholesterolemic, and normolipidemic subjects. The methodological soundness of the laboratory determinations of lipids and apo B is also an important issue. Concern has been raised regarding the measurement of apo B, but it is standardized, precise, and not expensive. Paradoxically, it is becoming ever more obvious that the methodological problems lie with calculated LDL cholesterol. To the known deficiencies must be added the fact that calculated LDL cholesterol systematically underestimates true LDL cholesterol at values close to target levels.Thus, from every perspective-pathophysiology, diagnosis, assessment of therapy, and methodologic soundness-there are powerful clinical arguments why apo B should be used in the routine diagnosis of dyslipidemias and assessment of the adequacy of statin therapy.