Bloodwork: Interpretation

On every blood test report there are three columns. The column on the left-hand side of the page is the name of the test run. The middle column is the specific results for the patient. And on the right side is the reference range. This may also be listed as a “normal range.” The reference range is usually treated as the “ideal” range by most practitioners. Patients are often told, “your results are in the reference range. You are good. You are fine. You are healthy. Don’t worry.” Often times the patient may say “I feel pretty crummy for someone whose labs say they are healthy. What’s the deal?” Well, the deal is, the reference range is not where the healthy people are, even though it is usually treated that way. This is why we need to write down for the patient where the healthy people are. If their result is not where the healthy people are, then we will wonder, “if we get them to where the healthy people are, will they feel like a healthy person again?”

So, what makes this so confusing for both patients and doctors? Well, the reference range is not based on where the healthy people are. Instead, it is based on statistics. Testing labs get a lot of different results from all the different people they run any one test on. The distribution of the results looks like a bell-shaped curve (Figure 6.6).

On the left is the lower end of the range and on the right is the higher end. Most results though are in the middle. If we were to test the height of 100 different people, some people would be quite short and some would be quite tall; however most people would be in the middle. Similarly, some people are quite thin while others are quite heavy. But most people are in the middle. The same is true with a grading curve in school. So, the testing labs say “how can we come up with some kind of reference range for reporting lab results? We know! We will use statistics!” And very arbitrarily, the labs say that two standard deviations of the mean will be the reference range we will put on this piece of paper. By definition, 95 out of every 100 results fall within two standard deviations of the mean. That is just the definition of two standard deviations from the mean. It doesn’t matter who is being tested. A bunch of sick people. A bunch of healthy people. A bunch of baboons. It is just statistics.

But labs typically tend to test people who aren’t feeling so well. So, people tend to get compared to people who don’t feel well, when they really want to know “so where am I compared with healthy people? How about those people who climb Mount Everest? Or astronauts? Where are they? I wouldn’t mind being where they are.” So, if a person ever gets flagged on a specific blood test

result as being either high or low, they can pretty much say right away that they are one of the 5 worst out of 100. They have gotten a grade of an “F” on this test. If they are not flagged, then they say “oh, I know how this works now. If I am not flagged on this test, it just means that I am not one of the 5 worst out of 100.1 am not an ‘F But what I am left with is that I am somewhere between a D- and an A+.” This is a very broad range. A grade of a C or a D is not an F, but it is definitely not an A either. A person wants to be in the A range. This is where human biochemistry and physiology work the best.

So how do we know where the “A” range is for the tests we run? Hundreds if not thousands of studies, some actually done on astronauts and people who have climbed Mount Everest, have told us where the human body needs to be to perform at its highest levels. This is the physiologic range, not the statistical range. As part of this chapter, you will see tables with the ideal ranges for all the tests commonly run (Tables 6.5, 6.6, 6.7). These numbers are always changing as more and more data come out. By the time this book is published, there may need to be some subtle modifications of these ideal numbers. The rule of thumb tends to be, though, that if something is good for us, we want to be in the high end of the range. If it is not good for us, it tends to mean we need to be in the lower end of the range.

This is also why you will see different reference ranges being used by different labs. You can tell a lot about the particular population being tested by a certain lab company by the reference ranges produced. A fasting blood sugar range of 70 to 100 mg/dL is a lot different than one that goes up to 110 mg/dL. The people in the latter community tend to have far higher fasting blood sugar than the

TABLE 6.5

Ideal Physiology Ranges

TABLE 6.6

Ideal Physiological Ranges: Women Only

Ideal Physiological Ranges of Commonly Run Lab Tests for Women (Fasting)

TABLE 6.7

Ideal Physiological Ranges: Men Only

Ideal Physiological Ranges of Commonly Run Lab Tests for Men (Fasting)

other population. The same is true for a lab with a vitamin D range of 10 to 50 ng/mL compared with a 20 to 80 ng/mL range.