WHAT IS “NORMAL” CHOLESTEROL?
One of my patients complained that clinicians “are making the whole country sick. Everyone is abnormal.” Laboratories don’t report values based on the normal curve anymore. Instead, a normal level is determined by committee, such as the National Cholesterol Education Program, and laboratories report “reference ranges.” A cholesterol of 240 mg/dL used to be considered normal. Nowadays, that level would probably be labeled abnormal. Many patients are put on the defensive by being told their lab values are abnormal. Clinicians need actual numbers and practical ways to determine the effect of various risk factors and whether a patient’s chances are better if he undergoes treatment, e.g., with a statin, or not.
—Eugene M. Guazzo, MD, Chaptico, Md.
Dr. Guazzo is correct—to a point. We have gotten away from using the normal curve for some lab values, but this is not necessarily a bad thing. For example, he cites formerly “normal” cholesterol values now called “abnormal” by a committee as a manifestation of the system gone off-kilter. I disagree. Fifty years ago, the average total serum cholesterol level in the United States ranged from 220-240 on a bell-shaped population curve, so a level <240 was considered normal but was really average. A desirable level is established by epidemiologic data (such as the Framingham survey) that determine the level at which the prevalence of cardiovascular events seems to climb precipitously. By that reckoning, a cholesterol level of 150 is the desirable target (JAMA. 1998;290:2099-2104), but anything <200 would be considered acceptable or “normal.” Today, thanks to diet and drugs, the average serum cholesterol value is between 200 and 210 (JAMA. 2005;294:1773-1781), and this decrease is reflected in lower cardiovascular mortality. When the average and normal values finally coincide, all controversy will cease! Finally, although total cholesterol was cited, the same argument re “average” vs. “normal” also applies to LDL, the main factor in CAD risk.—Peter F. Cohn, MD (105-7)