Free Testosterone Results, Equilibrium Ultrafiltration vs Calculators

[ResearchIt]

When measuring free testosterone, my understanding is the equilibrium ultrafiltration method is the most accurate and the calculators are much less useful.

As you can see below, my free testosterone measured 20.23 ng/dL (ref range 5.00 to 21.00) using equilibrium ultrafiltration (Labcorp 070038). On this lab I am in the upper 95% of Labcorp's reference range.

I don't know the free testosterone reference range for the ISSAM calculator. Does anyone know this? Anyhow, it shows my calculated free testosterone is 12.20 ng/dL, which seems low.

For TruT, my calculated free testosterone is 23.81 ng/dL (ref range 16.30 to 31.30) which is 50%, basically right in the middle of the reference range.

How should I interpret my free testosterone results? Just take Labcorp's results that I have high range free testosterone on the day of this lab? Or also consider the lower ISSAM result and middle range TruT result?

ISSAM (Free T range?)


Tru T (Free T range 16.3 to 31.3)

 

[msfarid]

I had the same issue before
Measured is different from calculated and Doctor ignored the lab result and decided to depend on calculated.
Actual he didn’t request the lab test , I paid extra and requested by myself thinking it may be accurate than calculated

 

[ResearchIt]

That's interesting the doctor would used calculated instead of measured.

Does anyone know the free testosterone reference range for the ISSAM calculator?

Free & Bioavailable Testosterone calculator

www.issam.ch

 

[tareload]

Would be the same as the reference range for fT by equlibrium dialysis (ED) methods assuming this calculator fits the ED data well. Oh wait, that's right we are still debating the fT by ED ref ranges and whether Vermeulen (ISSAM) or Tru-T is "right".

Public Service Announcement: "Piss Poor" Direct RIA fT measurement (HELP is on the way)

Hey Folks, thought I would update the graph for free T reference ranges based on LC-MS/MS+ED and compare with Labcorp's direct RIA fT reference range. What the hell do you do with with your direct fT measurement if you want to compare with equibrium dialysis reference ranges? Take the Labcorp...

www.excelmale.com

Does anyone know the free testosterone reference range for the ISSAM calculator?

@Cataceous has stated probably 10-20 ng/dl is "decent" which would line up kinda decently with Labcorp normal range for fT by ED (5 to 28 ng/dl).

Good post @ResearchIt. Would be fun to compare UF number from Labcorp against ED. Many times Quest and Labcorp fT by ED numbers will either agree with ISSAM (Vermeulen or cfTV) or Tru-T (cfTZ or Zakharov in above plot).

I haven't seen a parity plot of Labcorp UF method vs ED for fT. I am still betting on cfTV but happy to be proven wrong. We got no idea.

 

[Cataceous]

...
@Cataceous has stated probably 10-20 ng/dl is "decent" which would line up kinda decently with Labcorp normal range for fT by ED (5 to 28 ng/dl).
...

Data from this study yield a 2.5-97.5% range of 7.0-22.6 ng/dL. N=126, healthy men aged 20-45 years.

 

[FunkOdyssey]

This topic is of great interest to me as you'll know from my hypogonadism thread. What I think is remarkable is that the mean free testosterone from the FHS Gen 3 sample of 14.2 ng/dL is considered almost out-of-range high by some organizations like Quest and Mayo. I think that speaks to how sad a state most men are in at this point.

The Gen 3 normal range of 7.0 ng/dL - 23.0 ng/dL compares favorably with the one posted by Cataceous above. I maintain these are the sort of numbers we should be using for a benchmark. If you want the upper quartile free T of healthy young men, you're looking at something above 16.4 ng/dL.

 

[tareload]

What I think is remarkable is that the mean free testosterone from the FHS Gen 3 sample of 14.2 ng/dL is considered almost out-of-range high by some organizations like Quest and Mayo. I think that speaks to how sad a state most men are in at this point.

Or not all fT methods via LC-MS/MS are created equal. Based on plot above comparing reference laboratories it is safe to say they are not. Then a related question on cfTV or cfTZ being the better calculator. Can't answer that until we know how to measure fT. In my opinion TruT folks tend to ignore the data that undermines their calculator. But the first principles work they have done is inpressive.

See @madman posts on the CDC Host program and harmonizing fT methods.

 

[FunkOdyssey]

Or not all fT methods via LC-MS/MS are created equal. Based on plot above comparing reference laboratories it is safe to say they are not.

The problem is that we don't know how they are determining their reference ranges, so we can't necessarily assume that the different ranges imply a difference in test performance. Some labs decide to use the range from a reference sample like FHS Gen 3, and I've actually seen the Gen 3 total T range pop up on tests people are posting. These labs will have a high proportion of modern day men falling below the range, well in excess of 2.5%. Meanwhile, some labs generate their own reference range based on their own sample of tests they've performed. That's what I suspect Quest has done.

What someone ought to do for the sake of science is have back-to-back free T tests performed by Quest and Labcorp in the same day. I bet they would be nearly identical. I might do this someday.

 

[tareload]

back-to-back free T tests performed by Quest and Labcorp in the same day.

Truly for the tortured minds. I have pulled E2 by RIA and sensitive E2 same day and done replicates for CBC and E2 by RIA on same day for same lab (actually same vial)...long story.

E2 by RIA has about 15% difference between the two results. Quite eye opening. CBC was tighter.

 

[tareload]

free T tests performed by Quest and Labcorp

Quest:

Table 4. [Reference for Free Testosterone by Equilibrium Dialysis in Normal Men]. - Endotext - NCBI Bookshelf

 

[tareload]

I haven't seen a parity plot of Labcorp UF method vs ED for fT. I am still betting on cfTV but happy to be proven wrong.

Example:

Direct measurement of serum free testosterone by ultrafiltration followed by liquid chromatography tandem mass spectrometry

Currently there is no reliable method suitable for routine measurement of serum free testosterone (FT).To develop such a method involving liquid chrom…

www.sciencedirect.com