What Is a Lab Test Reference Range and How Are They Determined?
More Programs and Publications Featuring Dr. Brandy Gunsolus
In this program:
Are there some lab ranges under scrutiny that may require further research? How do I understand my normal? Hear from respected medical laboratory scientist Dr. Brandy Gunsolus.
Transcript
Ariqa Everett:
How are laboratory reference ranges determined? Are there some ranges that have more scrutiny and maybe require further research?
Dr. Brandy Gunsolus:
So this is one thing that I wish more people would know, or actually what is a reference range? So a reference range is where if you have 100 healthy people...
…and you were to test that marker, let's say TSH on those 100 people, you take the 95 people that are in the middle, and that is the range. It seems fairly arbitrary, it's not, it is embedded in statistics. And so 95 percent of the population will fall within the normal range, which also means that 5 percent of the population being completely healthy will normally fall outside of that range. Just because you have a value that falls outside of the reference range does not mean that there is something wrong. That's one thing that needs to be clear. I see a lot of patients that they say, "Oh, their CO2 is too high or this is 0.12 low," and it really doesn't mean as much as you might think just because there's a flag there. The other thing that people should know about reference ranges are that you can have shifts within that range and still be considered normal, but yet you're having symptoms of an issue and that's where you really need to look at your previous values to see has there been a shift.
Thyroid, especially THS, is very very common to have this where you can have a normal TSH value of say, 1.9 and then start being symptomatic of hypothyroidism and end up with a TSH of 5 and it's still in the normal range, but you are now having symptoms of low thyroid and yep, I said low because TSH is actually the opposite. So when it goes up, your thyroid is actually low. When the TSH goes down, your thyroid is actually overactive. So it's an opposite effect there. So just because something says that it's normal doesn't necessarily mean that it is. If you are having symptoms of something and your doctor just dismisses it says, "Hey, everything is normal", it's fine. Consider that these values do need a little bit more scrutiny.
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