LabCorp vs Quest Total T: Why the Discrepancy?

[jcmaxwell]

I have been following the same protocol for the last 12 months: 70 mg Test Cypionate twice weekly; 500 IU hCG twice weekly; 0.1 mg Anastrozole daily. I run blood tests just prior to the next injection cycle.

TOTAL TESTOSTERONE

1204 ng/dL LabCorp (Immunoassay 264-916) April 24

1891 ng/dL Quest (LC/MS/MS 250-1100) June 25

FREE TESTOSTERONE

>50 pg/mL LabCorp (Direct Immunoassay 6.6-18.1) April 24

548.2 pg/mL Quest (Dialysis) 35-155) June 25

E2, SENSITIVE

29.7 pg/mL LabCorp (LC/MS/MS 8-35) April 24

67 pg/mL Quest (LC/MS/MS) June 25

I fully understand that there is no correlation between free Testosterone Direct and free Testosterone by Dialysis, as they have completely different reference ranges. In fact, Direct Immunoassay fT has been completed discredited over the last 20 years. William Rosner wrote a scathing Letter to the Editor (July 2001, Journal of Endocrinology and Metabolism) entitled, “An Extraordinarily Inaccurate Assay for Free Testosterone is Still with Us”. He cited the work of Vermeulen and others demonstrating that Direct Immunoassay fT “is seriously inaccurate, underestimating its concentration by many-fold”.

But I do not understand why there is such a big difference between LabCorp’s and Quest’s Total Testosterone. Perhaps Nelson can offer his words of wisdom.

 

[Gman86]

Wow these are some huge differences. Do u happen to know ur SHBG? It must be super low. Around 10 I would imagine.

 

[jcmaxwell]

SHBG 24.6 (Lab Corp)

 

[fifty]

blood tests are a magic 8 ball.

 

[Gman86]

SHBG 24.6 (Lab Corp)

Wow, waaayyyy higher than I would of imagined. Just goes to show that either direct free T tests are highly inaccurate, or everyone’s SHBG varies on how strongly it binds to sex hormones.

 

[Nelson Vergel]

I have been following the same protocol for the last 12 months: 70 mg Test Cypionate twice weekly; 500 IU hCG twice weekly; 0.1 mg Anastrozole daily. I run blood tests just prior to the next injection cycle.

TOTAL TESTOSTERONE

1204 ng/dL LabCorp (Immunoassay 264-916) April 24

1891 ng/dL Quest (LC/MS/MS 250-1100) June 25

FREE TESTOSTERONE

>50 pg/mL LabCorp (Direct Immunoassay 6.6-18.1) April 24

548.2 pg/mL Quest (Dialysis) 35-155) June 25

E2, SENSITIVE

29.7 pg/mL LabCorp (LC/MS/MS 8-35) April 24

67 pg/mL Quest (LC/MS/MS) June 25

I fully understand that there is no correlation between free Testosterone Direct and free Testosterone by Dialysis, as they have completely different reference ranges. In fact, Direct Immunoassay fT has been completed discredited over the last 20 years. William Rosner wrote a scathing Letter to the Editor (July 2001, Journal of Endocrinology and Metabolism) entitled, “An Extraordinarily Inaccurate Assay for Free Testosterone is Still with Us”. He cited the work of Vermeulen and others demonstrating that Direct Immunoassay fT “is seriously inaccurate, underestimating its concentration by many-fold”.

But I do not understand why there is such a big difference between LabCorp’s and Quest’s Total Testosterone. Perhaps Nelson can offer his words of wisdom.

Different dates far apart. Different assay types (LC/MS has no interference with biotin, for example). Nothing is straight line even 2 days apart.

Quest has better free T ranges than LabCorp. The E2 range is more narrow and has a lower upper value.

 

[madman]

I have been following the same protocol for the last 12 months: 70 mg Test Cypionate twice weekly; 500 IU hCG twice weekly; 0.1 mg Anastrozole daily. I run blood tests just prior to the next injection cycle.

TOTAL TESTOSTERONE

1204 ng/dL LabCorp (Immunoassay 264-916) April 24

1891 ng/dL Quest (LC/MS/MS 250-1100) June 25

FREE TESTOSTERONE

>50 pg/mL LabCorp (Direct Immunoassay 6.6-18.1) April 24

548.2 pg/mL Quest (Dialysis) 35-155) June 25

E2, SENSITIVE

29.7 pg/mL LabCorp (LC/MS/MS 8-35) April 24

67 pg/mL Quest (LC/MS/MS) June 25

I fully understand that there is no correlation between free Testosterone Direct and free Testosterone by Dialysis, as they have completely different reference ranges. In fact, Direct Immunoassay fT has been completed discredited over the last 20 years. William Rosner wrote a scathing Letter to the Editor (July 2001, Journal of Endocrinology and Metabolism) entitled, “An Extraordinarily Inaccurate Assay for Free Testosterone is Still with Us”. He cited the work of Vermeulen and others demonstrating that Direct Immunoassay fT “is seriously inaccurate, underestimating its concentration by many-fold”.

But I do not understand why there is such a big difference between LabCorp’s and Quest’s Total Testosterone. Perhaps Nelson can offer his words of wisdom.

I have been following the same protocol for the last 12 months: 70 mg Test Cypionate twice weekly; 500 IU hCG twice weekly; 0.1 mg Anastrozole daily. I run blood tests just prior to the next injection cycle.

TOTAL TESTOSTERONE

1204 ng/dL LabCorp (Immunoassay 264-916) April 24

1891 ng/dL Quest (LC/MS/MS 250-1100) June 25

FREE TESTOSTERONE

>50 pg/mL LabCorp (Direct Immunoassay 6.6-18.1) April 24

548.2 pg/mL Quest (Dialysis) 35-155) June 25

E2, SENSITIVE

29.7 pg/mL LabCorp (LC/MS/MS 8-35) April 24

67 pg/mL Quest (LC/MS/MS) June 25

I fully understand that there is no correlation between free Testosterone Direct and free Testosterone by Dialysis, as they have completely different reference ranges. In fact, Direct Immunoassay fT has been completed discredited over the last 20 years. William Rosner wrote a scathing Letter to the Editor (July 2001, Journal of Endocrinology and Metabolism) entitled, “An Extraordinarily Inaccurate Assay for Free Testosterone is Still with Us”. He cited the work of Vermeulen and others demonstrating that Direct Immunoassay fT “is seriously inaccurate, underestimating its concentration by many-fold”.

But I do not understand why there is such a big difference between LabCorp’s and Quest’s Total Testosterone. Perhaps Nelson can offer his words of wisdom.

LC/MS-MS would be the more accurate assay mind you that is still a drastic difference.

When looking to compare would have been more sensible to have tested TT using both assays done on the same day April 24 using the same lab and even than again a few months later.

Was your protocol consistent (dose/injection frequency) as you are injecting both T/hCG twice weekly.

I would be more concerned as to why you are running such an absurdly high trough TT 1891 ng/dL (LC/MS-MS) 250-1100 and FT 548.2 pg/mL (Dialysis) 35-155.

These are trough levels as you are injecting twice weekly (every 3.5 days) so your peak TT/FT/e2 levels will be much higher.

Your FT level is 3.5X top end of the reference range and that is using the most accurate testing method (gold standard Equilibrium Dialysis).

You must be getting a significant bump in T from the hCG as you are hitting a trough TT of 1891 ng/dL and your T dose is only 70mg every 3.5 days (140mg/week).

No one needs to be running a TT trough of 1600-2000 ng/dL to achieve a healthy FT level even if one had higher SHBG.

You could easily manipulate your dose to bring your levels down and most likely drop the AI.

Do you have full labs to post and where does your RBCs/hemoglobin/hematocrit sit on such protocol?





Points to keep in mind:

*following a consistent protocol (dose/injection frequency/time of injections)

*using the most accurate assays such as TT (LC/MS-MS) and FT (Equilibrium Dialysis or Ultrafiltration)

* testing at the true trough which will vary depending on injection frequency

* using the same lab/time of testing




Everyone should be testing FT using the most accurate methods such as the gold standard Equilibrium Dialysis or Ultrafiltration (next best) if you truly want to know where your FT level truly sits on such protocol (dose of T/injection frequency).

Best bang for your buck:Total Testosterone (LC/MS- No Upper Limit) and Free Testosterone (Dialysis)

Total and Free Testosterone Test Panel plus Hematocrit

Lowest Cost Hematocrit, Total and Free Testosterone Test Panel for Men on TRT

www.discountedlabs.com

 

[jcmaxwell]

For simplicity, I will try to answer all the answers raised in one thread:

(1) “Do you have full labs to post and where does your RBCs/hemoglobin/hematocrit sit on such protocol?”

RBC 4.89 (4.40-6.00)

Hemoglobin 10.3 (13.5-17.0)

Hematocrit 33.3 (41-53)

MCV 68.2 (80 – 100)

MCH 21.0 (26 – 34)

MCHC 30.7 (31 – 37)

RDW 21.8 (less than 14.5)

Platelet Count 327 (150 – 450)

TIBC 364 (250-450)

UIBC 158 (111-343)

Iron 206 (38-169)

Iron Saturation 57 (15-55)

I have been diagnosed with microcytic hypochromic anemia.

(2) Was your protocol consistent (dose/injection frequency) as you are injecting both T/hCG twice weekly.

Yes, I have been running the same protocol (70 mg IM twice weekly, 500 IU hCG IM twice weekly, and 0.1 mg Anastrozole daily) for 12 months.

(3) Why are you using two different labs and two different assays for Total T?

The labs done on April 24 were ordered by a “famous” out-of-state provider who has a contract with Lab Corp to run a panel that includes immunoassay Total T and direct analog free T.

I ordered the tests done on June 25 through Discounted Labs, who recently switched from Lab Corp to Quest. I decided to run tests that had high sensitivity and selectivity, knowing that the free T and dialysis free T could not be compared, as I stated in the original post. My previous experience has been that LC/MS/MS Total T is generally slightly higher (100 ng/dL) than immunoassay Total T.

(4) You could easily manipulate your dose to bring your levels down and most likely drop the AI.

I needed an AI when my dose was 50 mg weekly and no hCG. (LabCorp Sensitive E2 was 88 pg/mL on that protocol.)

I plan on reducing hCG to 250 IU twice weekly. Do you think this will result in significant testicular shrinkage?

 

[jcmaxwell]

@Nelson and others: I want to throw one more monkey wrench into the discussion. My prolactin on April 24 was 49.7 ng/mL (LabCorp 4–15.2). I took cabergoline 0.5 mg weekly for 6 weeks and retested at Labcorp. The prolactin had dropped to 1.4 and I was told to discontinue cabergoline. For someone on exogenous testosterone, does prolactin affect the clearance of testosterone?