McCall McPherson explains that thyroid lab ranges differ between companies and locations because each lab generates them from its own patient population, typically sick people seeking answers. The "normal" values aren't based on healthy people, which can mislead clinical decisions.
Chapters
Normal in medicine, you think, well, there's an accepted range for blood sugar, there's an accepted range for cholesterol, for inflammatory markers, there has to be a normal accepted range for thyroid. There is not. So what's happening is clinicians look at patients' lab reports, they scan it, and they look for things in bold or off to the side, okay? If it's not in bold, if it's not off to the side, you're normal. The reason they do that and the way the mechanism that happens is They are basing their clinical decision on what the lab tells them is normal. Okay? So the lab arrives. If we're going to base our clinical decisions on what our patients look like, if they're normal, abnormal, we should be asking ourselves, how do they find these normal ranges? Because Quest Lab is different normal ranges than LabCorp.
Ugh.
Is different than the local hospital.
Oh my goodness.
In fact, Quest Lab by my house is different than Quest Lab by my office. So there is, they vary in and of themselves, even between locations. And the reason is because they collect samples of a bunch of patients and they formulate averages of patients in their database. They take, maybe they take out the extremes, top, bottom, and then they create averages and that's what's normal. So we should probably, again, ask ourselves who's going to the lab if we're going to base normal ranges of healthy people on this population of people. And the answer is not people who are like, oh my God, I feel so great on this Wednesday afternoon. I think I'll take a half day off work, go down to LabCorp and see what my thyroid looks like, right? You know, these people are sick. They're looking for answers. They're trying to find solutions. So, in essence, now we are basing normal labs off of sick people.
