The free t is a send out to arup labs. Online it didn’t state if it was a ultra filtration. It listed what is said above. I’ll post a link on my lunch break
Most likely this test?
Testosterone Free, Adult Male
Testosterone Free, Adult Male
Methodology
Quantitative Electrochemiluminescent Immunoassay
*Total Testosterone and SHBG are measured and free testosterone is estimated from these measurements
Interpretive Data
The concentration of free testosterone is derived from a mathematical expression based on the constant for the binding of testosterone to sex hormone binding globulin (SHBG).
So the free testosterone is done using the linear law-of-mass-action model.....most likely the Vermeulen calculated method
Free & Bioavailable Testosterone calculator
Notice beside the Calculate box
Explanation and examples
When you click on
Explanation and examples
This will show up at the top of the screen with an example of the calculation below.
Please find below an example of a calculation. The background on the validation of this method can be found:
“J Clin Endocrinol Metab 84:3666-3672, 1999 – A critical evaluation of simple methods for the estimation of free testosterone in serum”
“J Clin Endocrinol Metab 84:3666-3672, 1999 – A critical evaluation of simple methods for the estimation of free testosterone in serum”
A Critical Evaluation of Simple Methods for the Estimation of Free Testosterone in Serum
Alex Vermeulen Lieve Verdonck Jean M. Kaufman
The Journal of Clinical Endocrinology & Metabolism, Volume 84, Issue 10, 1 October 1999, Pages 3666–3672, Critical Evaluation of Simple Methods for the Estimation of Free Testosterone in Serum
Published: 01 October 1999
Critical Evaluation of Simple Methods for the Estimation of Free Testosterone in Serum
TruT™ by FPT
The novel, FDA-registered TruT™ algorithm uses modern understanding of molecular interactions to improve the accuracy of free-T calculations.
Why TruT™?
The only FDA-registered free testosterone calculator
- Improved biophysical characterizations have have suggested the importance of models that consider allosteric coupling of testosterone with dimeric SHBG. This model, as implemented by TruT™ provides the most accurate estimates for free testosterone.
- Commonly available free testosterone calculators (issam.ch, nebido.com, pctag.uk) use models of testosterone:SHBG binding (proposed by Vermeulen et al. and Sodergard et. al) which were developed before the crystal structure for SHBG:T complexes were available. These models assume that the two SHBG monomers behave identically in binding testosterone. Detailed experimental data show that the "simplified linear model is erroneous." References.
- The Endocrine Society has issued position statements which highlights the laboratory- and operator-dependent variability inherent in direct free testosterone measurements. For this reason they advocate for indirect "calculator" based methods References.
- The TruT™ calculator provides the ideal solution by using measurements of total testosterone, SHBG, and albumin to calculate free testosterone while taking into account the complex, non-linear allostery in SHBG's association with testosterone. TruT™ is the only calculator available that uses this more complex formulation. References
About the TruT™ free testosterone calculator
About TruT™
Current problems with accurate free testosterone determination
Current methods for measuring free testosterone (fT) are technically challenging and not accurate.
The widely used direct immunoassay and tracer analog techniques for measuring fT have been shown to be inaccurate. Equilibrium dialysis, the reference method against which other methods are compared, is labor-intensive and cumbersome, and therefore has had limited clinical adoption. As an alternative, free testosterone can be computed from the
total testosterone, SHBG, and albumin concentrations. Recently, Endocrine Society’s Expert Panel acknowledged the experimental problems in fT measurements and concluded that "...the calculation of free testosterone is the most useful estimate of free testosterone in plasma...
" However, we have demonstrated that even the calculated fT values derived from the prevailing equations, based on linear law-of-mass action models or empiric equations, differ systematically from free testosterone measured by equilibrium dialysis by as much as 40%.
Improved TruT™ Companion Diagnostics
Based on the fundamental discovery of testosterone partitioning, our team has developed an accurate free testosterone determination method. While examining the mechanistic origin of this systematic inaccuracy in free testosterone values using the linear model of SHBG:testosterone association, we discovered that the SHBG dimer exhibits conformational allostery in binding testosterone. Our TruT™ companion diagnostic, incorporating the correct parameters and non-linear dynamics in T:SHBG association has resulted in a framework for accurate determination of free testosterone values.
The TruT™ algorithm improves the accuracy of free-T calculations, reducing the potential for misdiagnosis, and better informing providers when designing treatments.
Current diagnostics, including the most widely used tracer analog method, have been shown to be inaccurate and its use is not recommended. Equilibrium dialysis is widely considered the reference method but most care providers and commercial laboratories do not offer equilibrium dialysis assays due to operational complexities in performing the assay and difficulties automating the procedure. Recognizing the practical difficulties that clinicians face in obtaining accurate measurement of free testosterone by equilibrium dialysis, an expert panel of the Endocrine Society concluded that "...calculated free testosterone, using high quality testosterone and SHBG assays, is the most useful clinical marker".
Our patent protected, novel TruT™ companion diagnostic framework provides accurate determination of free testosterone concentrations. This algorithm is based on experimental data demonstrating that testosterone’s binding to SHBG is a multi-step process involving an allosteric interaction between the two binding sites on the SHBG dimer. Estimates of free testosterone derived incorporating the allosteric coupling of SHBG monomers within the dimer provide accurate determination of free testosterone without systematic deviation from values obtained using equilibrium dialysis.
As you can see the Vermeulen method was developed before the crystal structure SHBG:T complex was known.
Commonly available free testosterone calculators (issam.ch, nebido.com, pctag.uk) use models of testosterone:SHBG binding (proposed by Vermeulen et al. and Sodergard et. al) which were developed before the crystal structure for SHBG:T complexes were available. These models assume that the two SHBG monomers behave identically in binding testosterone. Detailed experimental data show that the "simplified linear model is erroneous." References.
So the calculated free testosterone you are having done through ARUP Laboratories is using the Vermeulen linear law-of-mass-action model.....which is not going to be accurate.
Your best bet if you care about truly knowing what your FT level is would be to get the gold standard Equilibrium Dialysis or Ultrafiltration which are costly or simply getting TT (LC/MS-MS), SHBG and Albumin and use the newer calculated
TruT Free Testosterone Calculator by FPT .....online for free!
These would be the 2 options from Labcorp for accurate blood testing:
500726: Testosterone, Free, Mass Spectrometry... | LabCorp
Testosterone, Free, Mass Spectrometry/Equilibrium Dialysis (Endocrine Sciences)
TEST:
500726
Test number copied
CPT: 84402; 84403
070038: Testosterone, Free, Equilibrium Ultrafiltration... | LabCorp
Testosterone, Free, Equilibrium Ultrafiltration With Total Testosterone, LC/MS-MS
TEST:
070038
Test number copied
CPT: 84402; 84403
This would be an option from Quest
:
Quest Diagnostics: Test Directory
Testosterone, Free (Dialysis) and Total, MS
Test Code
36170
CPT Code(s)
84402, 84403
