WHAT IS A NORMAL CHOLESTEROL VALUE?

For some of the most important laboratory tests, the ones most of us worry about the most, the normal values on the lab printout sheet don’t seem to make much sense.  I am talking about the cholesterol and Triglyceride numbers, the blood sugar, the Hemoglobin A1c, and the Vitamin D level.  Let me try to explain. 

We all have an intuitive sense of what a normal lab value should mean: It is the range most heathy people will fall in.  For most laboratory tests, this is correct.  As I discussed in a previous post, for most lab tests what we call the “normal range,” which on the lab printout sheet will be labeled the “Reference Range,” is based on a statistical approach.  It is chosen so 95% of healthy people will fall in this range.  This is easy to understand.  It is true that a number of absolutely healthy people will have values outside this normal range, and I discussed the reasons for this in the previous post.

However, for a number of very important tests, the reference range is determined in a totally different way.  I like to call these reference ranges “Aspirational Normals,” because they reflect values a group of experts think we should aspire to, rather than any reality. 

The normal ranges for these tests come from the consensus of groups of self-proclaimed experts who meet and study a number of academic papers, many written by the members of the group itself.  Based on this, they then ascertain a range of values for this particular test they feel are most likely to lead to a longer life, or to some secondary goal that they deem important.  These are the numbers we are told to aspire to.  

Don’t misunderstand me.  I agree that many of these aspirations are worthy, just like the preacher’s admonitions in any Sunday sermon.  However, as is the case with the sermon, a large percentage of the population fall outside of these aspirational ranges.  This hardly makes you “abnormal” if you are one of them. 

At the request of these consensus groups and societies, the major laboratory companies, including Quest and LabCorp, give these aspirational values as the reference range for these tests.  Unfortunately, on their reports, the labs do not flag the tests whose “Reference Range” reflects hope and not reality.  This causes a lot of anxiety in a large number of people.  So, what percentage of the American population actually have lipid numbers that fall within the normal range? 

The real answer is that we just do not know.  The best available data comes from the CDC, which gets its information from what is known as the “CDC, Behavioral Risk Factor Surveillance System.”

The answer they come up with is that 33.5% of Americans over age 18 have an LDL cholesterol (often referred to as “bad cholesterol”) that they consider abnormal.  As for what they consider normal, they use the value of an LDL under 100, without really justifying this choice. I will note that the American Association of Clinical Endocrinologists generally targets 130, not 100. 

But, how does this survey get its information?  A group of government employees, university employees on contract, and commercial call centers on contract to the government phones random people and asks a series of questions about the health to whoever will talk to them. 

Now is the time to use common sense.  How many people actually will talk to callers trying to get you to take a survey?  Personally, I never do, and neither does my wife. And as for those who do choose to participate, do you think they represent a random cross section of the population, or are they somehow different than you or me?  Further, of those who will talk to the call center, how many do you think really have any idea what their LDL cholesterol number is, or even have a vague concept of what LDL cholesterol actually is.  Common sense tells you that the 33.5% quoted by the CDC is, in reality, a meaningless number. 

I wondered how close these estimates were to the people I actually see on our practice. As I have mentioned previously, this reflects a prepaid healthcare plan associated with a single large employer.  All of them are either employed or a spouse or child of an employee.   This means that none are truly indigent.  Also, very few are over age 65.   Although this may not reflect the entire American population. I think they do reflect what most of us would visualize as a group of normal people.   Actually, this group is probably healthier than the average American because only people who care about their health actually come to see us, and also because they are strongly encouraged to participate in a multitude of Wellness programs, all of which are free. 

What did I find?  I looked at 100 consecutive patients over the age of 18 that I saw recently.  42 had LDL cholesterol under 100 and were labeled as being in the reference range, or “normal.”  20 had LDL between 100 and 130, outside the LabCorp reference range, but on target according the American Association of Clinical Endocrinologists.  Another 20 had LDL over 130, and another 18 were being treated with statin medications.  In other words, 58% were “abnormal,” or out of the reference range.

When those experts tell us that the majority of people are abnormal, it really conflicts with our innate understanding of what the term normal means.  This defies Real Common Sense.

So, how should these cholesterol values be used, and who should get medications to lower their cholesterol?  That turns out to be a very tricky subject that will be the topic of an upcoming post concerning the “risk estimator tool” developed by the American Heart Association and the American College of Cardiology.  I promise, this will be a rant, because the approach they advocate completely defies Real Common Sense.  Stay tuned.