Response from LabCorp About Their Incorrect Unit Usages For Their Free Testosterone - Direct - Test

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bennettjc

Member
I've been irked for a year by the apparent incorrect unit usage for the particular Free Testosterone test mentioned above. I periodically reach out to whatever relevant executive I can find. No luck for months until the below correspondence. In brief his explanation doesn't hold up in my view. And his perspective seems to fall apart when the % free testosterone is looked at. But before I get back to them I would like some learned input....

Mr. XYZ

I wanted to reach out to someone at LabCorp regarding an issue I noticed. If you are not the right person please direct me in the right direction.

I am under treatment with testosterone replacement therapy. Hence frequently I get various testosterone tests done at LabCorp (my lab of choice).

And here at the VA I have been ordering similar levels for some of my patients and we happen to use LabCorp.

I've noticed that the units for the report for Free Testosterone Direct are incorrect. For example a report on me noted that my free testosterone was 2.4 pg/ml. (Total testosterone was 44ng/dl). The result for free testosterone should have been reported as 2.4 ng/dl. How do I know? Because if you covert 2.4 pg/ml to ng/dl (to be consistent with the units for total testosterone) you get .24 ng/dl. I knew that was wrong because that would mean my a free/total testosterone percentage of .55% which is way too low and is inconsistent with results from other times.

Please let me know if LabCorp is aware of this issue and what might be done.

This must be confusing to patients and providers (and patient-providers like me!).
Thanks So Much

Bennett Cohen MD

______________________________________________________________________

Subject: Re: [External] RE: Issue From A Provider/Patient

Dr Cohen - below is a message from our technical director Dr Andre Valcour:

The Direct Free Testosterone test produces numerical values that are approximately 10-fold lower than other commonly used free testosterone methods. This is based on way the assay is calibrated and is reflected in the reference ranges which are method specific. We offer the test in a manner that is consistent with the FDA cleared IFU. LabCorp has provided this test in this manner for many years (since the early eighties), and it is favored by many clinicians. In fact, it is by far the most popular test for free testosterone we offer. Clinicians are aware that the results must be considered in the context of the method-specific reference intervals. LabCorp offers a great variety of methods for measuring total and free testosterone. Our extensive menu is designed to fulfill the varied needs of all our clinician clients.

If you have further questions, I am happy to coordinate a discussion.

Best, Ben
 
Defy Medical TRT clinic doctor
They don't get it.


 
Well at least he admitted it was garbage in the first part of his response.
Then justifies it by saying well that's the way we've done it since the 80's.
No offense but are they passing out MD's like candy these days???
Other than the ones we know in our network of docs that title honestly doesn't mean much anymore sadly.
 
Well at least he admitted it was garbage in the first part of his response.
Then justifies it by saying well that's the way we've done it since the 80's.
No offense but are they passing out MD's like candy these days???
Other than the ones we know in our network of docs that title honestly doesn't mean much anymore sadly.
I checked out the good Dr. He does have an MBA. And he is a Dr. of biochemistry. No MD (yet).
 
Thanks for raising this issue and most people don't understand it very well. I don't blame them. However, the units used by Labcorp for the direct (RIA) free Testosterone assay are not incorrect. They are correct.

It's easy to think it's just a simple unit mislabel as I detail below in the attached posts. In reality the transfer function from direct (RIA) free T to calc-V Testosterone or Eq/LCMS Testosterone is typically closer to a factor of 5-7. All arcane but below you can find the details if you want the facts. Then this brings up the gory details of calculated free T vs measured EqD/LCMS free T (that's been beaten to death and not the topic at hand).

Nothing Valcour says above is wrong but it doesn't help explain the discrepancy. For the interested reader, I hope the following curated posts below help provide a useful resource to improve your understanding.

P.S. For the first appt I ever had on potential TRT I saw that the Dr. had ordered the direct free T assay and I spent the next 3 hours going through the details on why it was a problematic assay and not meaningfully physical when compared to human physiology as a % free T (as Dr. Cohen rightfully mentions in the original post above). Needless to say the Dr. laughed about it at the appt. As they say "ignorance is bliss" and understanding this stuff doesn't really lead to happiness.

Have a great day.




From this post as summary of how the math works out in an "easy" to understand example:

In summary, a poor guy with high SHBG:
Total T = 1077 ng/dL
SHBG = 151 nmol/L

  • “Direct” RIA free T comes back = 0.72 ng/dL (0.067% of total T)
  • Calculated free T by Vermuelen = 7.57 ng/dL (0.7% of free T)
  • Calculated free T by Tru-T = 25.3 ng/dL (2.35% of free T)
  • Actual free T as measured by equilibrium dialysis probably 5-6 ng/dL (0.46-56% of free T)
So what’s the average guy to do if he really wants to understand his free T status? You can even argue about the validity of indirect vs direct equilbrium dialysis measurements and which one is correct if they don’t match. In short, it gets complicated.

EDIT: as I posted below, if you take the RIA result and multiply by 6.7:
0.72 ng/dL * 6.7 = 4.8 ng/dL which is very close to the range of 5-6 ng/dL I estimated would be shown via equilbrium dialysis. So if you want to convert your free T (via direct RIA) number to what it would be if your physician actually had ordered an appropriate test, then multiply by 7 not 10.



 
Last edited by a moderator:
Thanks for raising this issue and most people don't understand it very well. I don't blame them. However, the units used by Labcorp for the direct (RIA) free Testosterone assay are not incorrect. They are correct.

It's easy to think it's just a simple unit mislabel as I detail below in the attached posts. In reality the transfer function from direct (RIA) free T to calc-V Test or Eq/LCMS Testosterone is typically closer to a factor of 5-7. All arcane but below you can find the details if you want the facts. Then this brings up the gory details of calculated free T vs measured LCMS free T (that's been beaten to death and not the topic at hand). Nothing Valcour says above is wrong but it doesn't help explain the discrepancy. For the interested reader, I hope this helps.





Thank you so much for the look behind the curtain! You have precluded me from having a potentially embarrassing talk with a PHD in Biochemistry. Despite my being convinced now that this is not a mislabeling per se it nevertheless is a source of confusion for scores of patients and providers. I know it was for me. And now I spend time on other forums explaining to other patients that no their Free Testosterone is in fact 30 rather than 3 given while their Total Testosterone is 1000ng/dl.
Bennett
 
Thanks for raising this issue and most people don't understand it very well. I don't blame them. However, the units used by Labcorp for the direct (RIA) free Testosterone assay are not incorrect. They are correct.

It's easy to think it's just a simple unit mislabel as I detail below in the attached posts. In reality the transfer function from direct (RIA) free T to calc-V Testosterone or Eq/LCMS Testosterone is typically closer to a factor of 5-7. All arcane but below you can find the details if you want the facts. Then this brings up the gory details of calculated free T vs measured EqD/LCMS free T (that's been beaten to death and not the topic at hand).

Nothing Valcour says above is wrong but it doesn't help explain the discrepancy. For the interested reader, I hope the following curated posts below help provide a useful resource to improve your understanding.

P.S. For the first appt I ever had on potential TRT I saw that the Dr. had ordered the direct free T assay and I spent the next 3 hours going through the details on why it was a problematic assay and not meaningfully physical when compared to human physiology as a % free T (as Dr. Cohen rightfully mentions in the original post above). Needless to say the Dr. laughed about it at the appt. As they say "ignorance is bliss" and understanding this stuff doesn't really lead to happiness.

Have a great day.




From this post as summary of how the math works out in an "easy" to understand example:

In summary, a poor guy with high SHBG:
Total T = 1077 ng/dL
SHBG = 151 nmol/L

  • “Direct” RIA free T comes back = 0.72 ng/dL (0.067% of total T)
  • Calculated free T by Vermuelen = 7.57 ng/dL (0.7% of free T)
  • Calculated free T by Tru-T = 25.3 ng/dL (2.35% of free T)
  • Actual free T as measured by equilibrium dialysis probably 5-6 ng/dL (0.46-56% of free T)
So what’s the average guy to do if he really wants to understand his free T status? You can even argue about the validity of indirect vs direct equilbrium dialysis measurements and which one is correct if they don’t match. In short, it gets complicated.

EDIT: as I posted below, if you take the RIA result and multiply by 6.7:
0.72 ng/dL * 6.7 = 4.8 ng/dL which is very close to the range of 5-6 ng/dL I estimated would be shown via equilbrium dialysis. So if you want to convert your free T (via direct RIA) number to what it would be if your physician actually had ordered an appropriate test, then multiply by 7 not 10.



By the way - I am trying to figure out how best to respond to Dr. Vancour. I am speaking to some state of the art TRT providers (in my view) on other forums and gathering opinions. If Dr. Vancour is receptive would you be interested in communicating directly with him?
 
Contact from Dr. Vancour:

Dr. Cohen,

LabCorp offers a great variety of methods for measuring total and free testosterone. The attached document lists all of our many options available. Please note that you can find more information about these panels through our online directory of services. To reach this site, simply Google “LabCorp test menu”. Then type in the test number of interest from the attached sheet. You should find a nice description of each test and how it is performed. Also of interest might be example reports attached to these pages under “Related Information”.

While various methods report in a variety of units, they all provide method-specific reference intervals. Our extensive menu is designed to fulfill the varied needs of all our clinician clients.

If you or anyone in your group has any further information, please do not hesitate to reach out to me.

Andre Valcour, MBA, PhD, D(ABCC)


Very political response.....

I am planning to get back to him in a couple of days. I'm going include the input (no names) I've gotten here and elsewhere.

@Nelson Vergel - Can I get nudge you to say something to LabCrop/Dr. V through me? Your expertise and experience in this particular area would be of great value.

Thanks all!
Bennett
 
LabCorp reports free testosterone that do not make sense even in their "direct" method that goes along with LC/MS.

Example:

testosterone labcorp.jpg


Free testosterone is around 2% of total testosterone.

In this example, Total Testosterone is 435.8 ng/dL

Two percent of that is 0.02 x 435.8 nd/dL= 8.72 ng/dL= 87.2 pg/mL (units used for free T)

His Free T was reported as 16 pg/mL which is absurd.

Here is an example from Quest (for this test Testosterone, Free, Bioavailable and Total (Upper Limit T 1,500 ng/dL) plus SHBG)


Quest testosterone ranges and units.jpg


This is the total Testosterone by LC/MS and free T by dialysis
testosterone test lc ms quest.jpg




Quest has a reasonable range AND units.

I have emailed LabCorp several times about this but they ignore it. Dr Saya has done the same thing.
 
It may be inaccurate but it is widely ordered by clinicians and is leading to confusion among patients.
Ok, but why invest a lot of energy rearranging deck chairs on the Titanic? Why not promote the more accurate tests instead, equilibrium dialysis or ultrafiltration? The direct test simply doesn't correlate well with these more accurate tests. You can't just apply a scale factor and claim to have the right result. Even the calculated methods are better, albeit imperfect. Not to mention: LabCorp would cause chaos if they suddenly applied the scale factor and changed the units. It's not going to happen. The most graceful way to beat this dead horse is for LabCorp to create a new test number that uses the same test and reports the scaled result.
 
k, but why invest a lot of energy rearranging deck chairs on the Titanic? Why not promote the more accurate tests instead, equilibrium dialysis or ultrafiltration?
Because it is cheaper and works fine with moderate levels of testosterone under 1000 ng/dL. LC/MS TT plus Eq. Dialysis Free T also takes 3 to 4 more days to get results.
 
Because it is cheaper and works fine with moderate levels of testosterone under 1000 ng/dL. LC/MS TT plus Eq. Dialysis Free T also takes 3 to 4 more days to get results.
I have to disagree. Even at modest levels of testosterone the test is unusable. My own results show this quite well. Free testosterone should be pretty proportional to dose, but the direct test goes down in flames:
Direct Free T Response to Dose.png

Updated Tru-T vs Dose, 7 points.jpg
 
LabCorp reports free testosterone in the wrong units.

Example:

View attachment 12602

Free testosterone is around 2% of total testosterone.

In this example, Total Testosterone is 435.8 ng/dL

Two percent of that is 0.02 x 435.8 nd/dL= 8.72 ng/dL= 87.2 pg/mL (units used for free T)

His Free T was reported as 16 pg/mL which is absurd.

I have emailed LabCorp several times about this but they ignore it.
Hi Nelson

So for those of us that have had this LabCorp Test in the past, was it a waste of time and money or can the data be manipulated (mathematically or via the units used) to make the Free T data useable in our history files?
 
That is debatable. Free testosterone is NOT fully proportional to T dose. As dose increases, the relative increase of free T is larger due to decreases in SHBG.
 
LabCorp reports free testosterone in the wrong units.

Example:

View attachment 12602

Free testosterone is around 2% of total testosterone.

In this example, Total Testosterone is 435.8 ng/dL

Two percent of that is 0.02 x 435.8 nd/dL= 8.72 ng/dL= 87.2 pg/mL (units used for free T)

His Free T was reported as 16 pg/mL which is absurd.

Here is an example from Quest (for this test Testosterone, Free, Bioavailable and Total (Upper Limit T 1,500 ng/dL) plus SHBG)

View attachment 12603

Quest has the right range AND units.

I have emailed LabCorp several times about this but they ignore it. Dr Saya has done the same thing.
@Nelson Vergel @Dr Justin Saya MD - Gentlemen, I have Dr. Valcour at LabCorp waiting to hear back from me. This might be an opportunity to have some impact. Do either or both of you have any interest in helping me draft a response to him or simply doing a 3 person letter? You've both been through this issue with LabCorp before and are better versed in the issues. Please PM me if there is interest.
Bennett
 
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