Quest diagnostics free t range

[goolapsh]

Quest tops off at 155pg\ml (15.5ng/dl) when it is generally considered (on this forum at least) that free t should be 20-30 ng/ml. So who’s right? Should we be aiming for a max of 15.5ng/dl?

 

[JimGainz]

That range at Quest is bogus - and only used when the diagnostic is hypogonadism. Most doctors are not aware of this and mistakenly assume a Free Test level of 7 ng/dl is the midpoint range - when actually it’s in the lower end. This lab test kept me off TRT for years when I could have used it because doctors were uninformed. Ideally you want it over 20.

 

[goolapsh]

That range at Quest is bogus - and only used when the diagnostic is hypogonadism. Most doctors are not aware of this and mistakenly assume a Free Test level of 7 ng/dl is the midpoint range - when actually it’s in the lower end. This lab test kept me off TRT for years when I could have used it because doctors were uninformed. Ideally you want it over 20.

where are you getting your info from that optimal free t is over 20? I’m not saying you’re wrong but ranges don’t come out of thin air. I’m genuinely curious.

 

[JimGainz]

where are you getting your info from that optimal free t is over 20? I’m not saying you’re wrong but ranges don’t come out of thin air. I’m genuinely curious.

Most TRT clinics, including Defy aim for a number in the 20s - to match a youthful male. This was based off of numerous consultations as well as watching other TRT docs on YouTube and reading threads on this forum.

Personally, to get mine that high I need a corresponding Total T in the 1200s which causes me to take lots more arimidex than I like. Currently I am at 800 total and free T somewhere between 15 and 18 and feel fine.

 

[JimGainz]

where are you getting your info from that optimal free t is over 20? I’m not saying you’re wrong but ranges don’t come out of thin air. I’m genuinely curious.

Also the top end of the free T range is actually 28 or 30 ( including quest when the diagnoses is not hypogonadism) so over 20 is in the top quartile.

 

[JimGainz]

Also the top end of the free T range is actually 28 or 30 ( including quest when the diagnoses is not hypogonadism) so over 20 is in the top quartile.

I should have been clearer with my responses. Free T range is up to 30. Quest does this weird thing where they cut the top end of the range in half when they are looking for hypogonadism (no idea why) so the range will be up to 15. The problem with this is that when a guy shows up with a 7 free t score as I did, doctors assume you are at the midpoint of the range. Labcorp doesn’t do this quirky thing. So you need to be armed with this information when speaking to doctors. If you go to the Quest site you can search for lab tests and you can see the real range for free T - or just Google it. That’s why clinics shoot for over 20 which is the upper range for men.

 

[goolapsh]

I should have been clearer with my responses. Free T range is up to 30. Quest does this weird thing where they cut the top end of the range in half when they are looking for hypogonadism (no idea why) so the range will be up to 15. The problem with this is that when a guy shows up with a 7 free t score as I did, doctors assume you are at the midpoint of the range. Labcorp doesn’t do this quirky thing. So you need to be armed with this information when speaking to doctors. If you go to the Quest site you can search for lab tests and you can see the real range for free T - or just Google it. That’s why clinics shoot for over 20 which is the upper range for men.

Just curious. What is your regimen? How much anastrozole are you taking ?

 

[Cataceous]

That range at Quest is bogus - and only used when the diagnostic is hypogonadism. ...

This is readily disproved by the test's information sheet. The interpretive information lists many conditions linked to excessive testosterone, in addition to ones related to low testosterone. The more valid complaint is that nearly every free testosterone testing method or calculation has its own unique reference range. No direct comparisons between these are possible.

 

[xqfq]

For what it's worth:

Same day, 15 minutes apart:

Quest: 189.4 pg/mL (Range: 35.0-155.0 pg/mL)
Labcorp: 21.8 pg/mL

Six days apart, same protocol:

Quest 155.4 pg/mL (Range: 35.0-155.0 pg/mL)
Labcorp: 10.4 pg/mL (Range: 8.7 - 25.1)

 

[JimGainz]

This is readily disproved by the test's information sheet. The interpretive information lists many conditions linked to excessive testosterone, in addition to ones related to low testosterone. The more valid complaint is that nearly every free testosterone testing method or calculation has its own unique reference range. No direct comparisons between these are possible.

I just googled it I am on the site right now and the Free Test range for 18 to 69 year olds is up to 224 pg/ml It’s test code 18944.

 

[JimGainz]

I just googled it I am on the site right now and the Free Test range for 18 to 69 year olds is up to 224 pg/ml It’s test code 18944.

So I think I see what’s going on – the test that I referenced looks like it’s to assess overall testicular health in men, whereas the test sheet that was referenced above is part of a broader testosterone assessment and specifically for prepubescent children, hypogonadal men and virtualizing women – which is probably why they lower the range.

 

[Cataceous]

So I think I see what’s going on – the test that I referenced looks like it’s to assess overall testicular health in men, whereas the test sheet that was referenced above is part of a broader testosterone assessment and specifically for prepubescent children, hypogonadal men and virtualizing women – which is probably why they lower the range.

Negative. The reference ranges are for normal populations, period. The two tests use different technologies, which result in different proxies for free testosterone that cannot be directly compared. The dialysis-based test is capable of much better accuracy, and also greater sensitivity at low levels. This latter characteristic is what makes it better suited for populations with lower testosterone. However, the immunoassay test you reference is probably so inaccurate that it shouldn't be used for anything.

 

[JimGainz]

Negative. The reference ranges are for normal populations, period. The two tests use different technologies, which result in different proxies for free testosterone that cannot be directly compared. The dialysis-based test is capable of much better accuracy, and also greater sensitivity at low levels. This latter characteristic is what makes it better suited for populations with lower testosterone. However. the immunoassay test you reference is probably so inaccurate that it shouldn't be used for anything.

Ok but, Picograms per deciliter would be the same units of measurement regardless of the lab utilized for the assessment, no? I just went back and reviewed some of my old labs from Quest when my testosterone dose was much higher and it had me at 1088 Total Test and 295 Free Test. Same test that had the max at 155 pg/dl. If the range at quest was the true upper limit and maxed by their testing protocol, I would be at twice the maximum level for male, which wouldn’t be possible. I’m going to have to call them and see what they say.

 

[Cataceous]

Ok but, Picograms per deciliter would be the same units of measurement regardless of the lab utilized for the assessment, no? I just went back and reviewed some of my old labs from Quest when my testosterone dose was much higher and it had me at 1088 Total Test and 295 Free Test. Same test that had the max at 155 pg/dl. If the range at quest was the true upper limit and maxed by their testing protocol, I would be at twice the maximum level for male, which wouldn’t be possible. I’m going to have to call them and see what they say.

If there's no harmonization between the different testing methods then the units are virtually meaningless. A lab could say its free T results are in furlongs per fortnight and it wouldn't change anything as long as the reference range was in the same units. At present you can compare these free T measurements only to the reference range or to other results acquired using the exact same test.

The reference range is different from the capabilities of the test. The standard definition for a reference range includes 95% of the normal population. This is the range that includes from two standard deviations below the mean to two standard deviations above the mean. It says nothing about the maximum possible value a particular testing method can measure. That must be stated separately. If your measured free testosterone is at twice the top of the reference range it means that only an exceedingly tiny fraction of men, if any, might naturally have such levels.

 

[hurleytmark]

That range at Quest is bogus - and only used when the diagnostic is hypogonadism. Most doctors are not aware of this and mistakenly assume a Free Test level of 7 ng/dl is the midpoint range - when actually it’s in the lower end. This lab test kept me off TRT for years when I could have used it because doctors were uninformed. Ideally you want it over 20.

NOT ALL ranges are treated the same!!! They use different methods to measure it and hence, the #'s will vary!

 

[tareload]

A lab could say its free T results are in furlongs per fortnight and it wouldn't change anything as long as the reference range was in the same units.

I'd definitely take issue with that lab. Dimensional analysis would reveal their units indicate a speed (distance per unit time) instead of a concentration (chemical moles or mass per unit volume).

But I realize you are most likely exaggerating for effect; I'm also guilty sometimes .

Ahh, the wonderful arcane corner of the world dealing with fT measurement. The gift that keeps on giving.


BTW, these are fun quick reads if anyone interested:

Furlongs per Fortnight | The Metric Maven

themetricmaven.com

Feral Units Endanger Our Health | The Metric Maven

themetricmaven.com

Always useful to know the thickness of a sheet of standard 20 lb paper in mils. Great trivia for dinner parties.

 

[Cataceous]

I'd definitely take issue with that lab. Dimensional analysis would reveal their units indicate a speed (distance per unit time) instead of a concentration (chemical moles or mass per unit volume).
...

But that's just a phonetic English rendering of the actual units, which are frrlngzzzz per frrrtnyt, which of course is a mass per volume. Maybe it would be less confusing to use the meeetreec system's frashistans per clumpher.

The point is that if results from different labs cannot be compared then the units are basically arbitrary, at least from the point of view of the end user.

 

[tareload]

The point is that if results from different labs cannot be compared then the units are basically arbitrary, at least from the point of view of the end user.

LabCorp Vs Quest free testosterone lab ranges: Why are they different?

Thanks for all the information, this is really helpful. I had no idea Labcorp only had the Direct method for Free T. I'm doing my labs through discountedlabs and I think they only use Quest Diagnostics, so that's good. Not true. Lab Corp has more than six total and free testosterone assays...

www.excelmale.com

I happily compare them. Lower limits are pretty comparable (one of these isn't like the others); upper limits do vary more.

I agree will be great to bring standardization to fT measurement.



@bixt: to your point yesterday you can see where cfT-z really strays from all other reference labs' lower limits due to the issue you daylighted again.

Detailed summary:

Calculate Free Testosterone with TruT by FPT

[0026] Fig. 7 depicts the thermodynamic Parameters associated with testosterone's binding to SHBG derived from the fit of binding isotherms and ITC data to new model. While this parameter set is not unique, together they consistently describe the binding isotherms, depletion curves and ITC data...

www.excelmale.com

 

[tareload]

frashistans per clumpher

Now those are some units we can all get behind!

then the units are basically arbitrary, at least from the point of view of the end user.

I understand your POV. The end user is typically completely confused with this mess.

 

[Cataceous]

LabCorp Vs Quest free testosterone lab ranges: Why are they different?

Thanks for all the information, this is really helpful. I had no idea Labcorp only had the Direct method for Free T. I'm doing my labs through discountedlabs and I think they only use Quest Diagnostics, so that's good. Not true. Lab Corp has more than six total and free testosterone assays...

www.excelmale.com

I happily compare them. Lower limits are pretty comparable (one of these isn't like the others); upper limits do vary more.

I agree will be great to bring standardization to fT measurement.
...

Let's look at those reference ranges on a linear scale, and not even bother with cFTZ. Maybe one could compare Quest values to Mayo values, but anything else would seem to require some data massaging.