Warning: Quest Diagnostics Free Testosterone Reference Range

After looking through past bloodwork and scratching my head over a few things, I realized my lab changed up free testosterone tests on me.

My sample was originally sent to Labcorp (Test # 500726) with a reference range of
52-280 pg/mL.
My followup BW was analyzed at Quest (Test # 15988 I believe) and their reference range was
35-155.0 pg/mL.
Since the top of Quest's range was MUCH lower, I got flagged as high (210 pg/mL) when I would be well within range according to Labcorp's test.

Just wanted to give you guys a heads up, hope everyone's journey is going well.

Different tests cannot be compared directly, even if the numbers are the same. The reason for this is mainly that they might (probably) use different equipment, techniques, etc...

It's one reason we emphasize getting the same test done at the same lab to compare. I'm not saying you wouldn't have been in range on the labcorp test, but I am saying it's reasonable to presume you could have been out of range on both, or one but not the other, etc...

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Originally Posted by HRTstudent

Different tests cannot be compared directly, even if the numbers are the same. The reason for this is mainly that they might (probably) use different equipment, techniques, etc...

It's one reason we emphasize getting the same test done at the same lab to compare. I'm not saying you wouldn't have been in range on the labcorp test, but I am saying it's reasonable to presume you could have been out of range on both, or one but not the other, etc...

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Very true point. I forgot to qualify my statements, but I've read the same complaints from others about this test. Some doctors also distrust Quest due to errors in their test results, etc.

Labcorp updated their ranges not too long ago, I think 6 months, to reflect new information. Quest has not followed suit. So Labcorp and Quest now have different ranges on "normal" hormone levels.

At least I think it was Labcorp that changed, I could have the two reversed.

HRTStudent's claim that different labs results mean different things even if the numbers match is not really an accurate statement in so much as the conclusion some people come to. The national labs are very accurate, and yes Labcorp and Quest may vary slightly if they test the same sample, but that difference would be so small that it is not worth considering. If your actaul Free T is 200 and Labcorp says it's 199 but Quest says 201, what does it really matter? They results won't come back 180 and 220, they will be off only by one point if it was in fact the same sample tested.