Understanding Your Cholesterol Lab Work

Dr. William Davis Health Pro March 30, 2008
  • Warren, a 56-year old accounting manager at a manufacturing plant, recently came to my office and asked, "My doctor said my LDL cholesterol was 141. He said that's too high. But I've talked this over with some of my co-workers, and they tell me that they had LDL cholesterols a lot higher than that. Is my LDL really too high?"

     

    At first blush, it sounds like a straightforward question: Either cholesterol is too high and you'll have heart disease in your future, or it's low and you won't. Period.

     

    Not so fast. There are a number of issues to factor into you and your doctor's thinking and decision making about cholesterol. Unfortunately, it's not just a matter of just too high or too low.

     

    By current conventional advice (the consensus statement as issued by the National Cholesterol Education Panel via the Adult Treatment Panel-III, or ATP-III, the most recent and broad applied guidelines followed by most doctors), the following general scheme is advised (see below). You will notice that the principal focus of the guidelines is LDL cholesterol--LDL cholesterol is the number one determinant of heart disease risk, it is the number one reason drugs are prescribed; all else follows LDL.

     

    ATP III Consensus Guidelines: Classification of LDL, Total, and HDL Cholesterol (2001)

     

    LDL Cholesterol (mg/dl)

    <100 Optimal

    100-129 Near optimal/above optimal

    130-159 Borderline high

    160-189 High

    >190 Very high

     

    Total Cholesterol (mg/dl)

    <200 Desirable

    200-239 Borderline high

    >240 High

     

    HDL Cholesterol (mg/dl)

    <40 Low

    >60 High

     

    ATP-III provides for adjustment of target LDL cholesterol based on risk factors in a specific individual. They define "risk factors" as:

    Cigarette smoking

     

    Hypertension (BP>140/90 mmHg or on antihypertensive medication)

    Low HDL cholesterol (<40 mg/dL)

    Family history of premature CHD (CHD in male first degree relative <55

    years; CHD in female first degree relative <65 years)

    Age (men >45 years; women >55 years)

    LDL cholesterol targets are adjusted:

     

    If coronary heart disease or "risk equivalents" are present (e.g., diabetes or other forms of atherosclerotic disease such as aortic aneurysm or carotid disease causing symptoms) LDL target <100 mg/dl

     

    Multiple (2+) risk factors LDL target <130 mg/dl

     

    Zero to one risk factor LDL target <160 mg/dl

    More recently, in 2004, the ATP-III LDL target was optionally reduced to 70 mg/dl in people felt to be at particularly high-risk, such as recent heart attack survivors, smokers, or people with combined diabetes and heart disease, based on the favorable outcomes of some of the clinical trials of more intensive LDL cholesterol reduction by statin drugs.

    From Third Report of the Expert Panel on Detection, Evaluation, and Treatment of the High Blood Cholesterol in Adults (Adult Treatment Panel III): Executive Summary, 2001

    What the ATP-III guidelines and your doctor probably won't tell you:

     

    If I were to echo conventional advice, I would refer you to the guidelines provided by ATP-III, then say "Discuss it with your doctor." You and your doctor would then be taking notes from the same page.

  •  

    But I won't.

     

    Though, in my view, the guidelines provided by ATP-III are helpful as a starting point for crude advice on cholesterol, for truly effective advice on how to gain control over heart health, you need to go further.

     

    First of all, let's dismiss the value of total cholesterol. Total cholesterol is the combination of LDL ("bad") cholesterol, HDL ("good") cholesterol, and triglycerides (another "bad" blood fat), all lumped together. Total cholesterol is therefore a mixture of both good and bad factors and can yield confusing, often misleading, information. If, for instance, HDL goes way up (a good thing), so does total cholesterol (an apparently bad thing). That makes no sense. Yes, total cholesterol can serve to predict heart disease on a broad statistical basis in a large population. But you're just one person, not thousands. You require information that applies to you.

     

    Two, the LDL cholesterol number provided by your doctor is not actually measured, but calculated. It is calculated from the three other measured values (total cholesterol, HDL, triglycerides) by a nearly 50-year old equation, known as "the Friedewald equation". Dr William Friedewald developed this equation years ago, when measured LDL cholesterol values were not widely available and the equation was a necessity. When measured more precisely, calculated LDL is commonly 20, 40, 50% or more inaccurate. It can be higher, it can be lower, but you and your doctor can't tell which just by looking at the calculated LDL.

     

    Calculated LDL cholesterol by the Friedewald equation has about much remaining value as tie-dye T-shirts and hippie haircuts. It was relevant for its time, but it is starting to get faded and worn. More recent analyses have suggested that, while the higher LDL cholesterol is, the greater the risk for heart disease, many people with low cholesterols can also have substantial risk and that not everybody with high cholesterol does indeed face increased risk. How to make sense out of this jumble? No wonder it's not clear what exactly is a "high" cholesterol!

     

    Fast forward 50 years from Dr. Friedewald's day and LDL cholesterol is now widely available as a measured value. Even better, it is available as a superior measure, one that possesses superior power to predict whether heart disease is in your future or not.

     

    Allow me to make a set of bold predictions for the future:

     

    One: Total cholesterol will join 8-track tape players in the junk heap of technology, and you will no longer see it on your standard cholesterol panel.

     

    Two: Calculated LDL cholesterol will become less and less the number used to gauge risk from cholesterol issues. More accurate measures like measured LDL, apoprotein B, and my favorite, LDL particle number (obtained through a more sophisticated though highly accurate test called the NMR LipoProfile, Liposcience), will replace this rusty old model-T called calculated LDL. Measured LDL and apoprotein B are already available in most modern laboratories; the NMR and other lipoprotein tests are also available, but must be specified by your doctor.

  •  

    Three: Even with measures superior to calculated LDL, your doctor will pay more attention to HDL and triglycerides, both values that yield a wealth of information about your eating habits, genetics, and future potential for heart disease.

     

    Four: Measures that go even further than the cholesterol panel, measured or calculated, will become mainstream. This may include measures of high-risk for heart disease like lipoprotein(a) and C-reactive protein and other indexes of hidden inflammation. Although all cholesterol panels are now drawn while you are fasting, there will be a time when we also examine blood patterns immediately after eating to study how you handle food digestive by-products. This, too, can shed light on heart disease risk.

     

    Five: Examination of your risk factors will always be conducted in tandem with measures of the disease itself. In other words, risk factors will not be viewed in isolation, but as a part of an overall view of you and your risk by factoring in whether or not and how much atherosclerosis you may already have. This way, a person with advanced coronary atherosclerosis will be viewed differently (and treated more intensively) than someone with similar blood patterns but no disease whatsoever.

     

     

    For some, the future is now, and these more advanced concepts are already underway. But mainstream preventive cardiology, I predict, will follow this blueprint for development over the next decade.

     

    So if you and your doctor decide to adhere to the ATP-III guidelines for LDL cholesterol, fine. You can get some rough sense for what is desirable and what is not that way.

     

    But if you want something better, it's time to starting being aware of all the additional ways to improve the power to predict and gain control over risk for heart disease.