Direct vs Equilibrium

[jsmith21896]

I just ordered some blood work through discountedlabs.com, I noticed that the total/free test I selected is by equilibrium analysis, usually when my Dr. orders the free test it's by Direct. Also, is this the same as Equilibrium Dialysis, I did some looking around and that is all I could find. Is this ok and which is preferred? Thanks.

 

[madman]

I just ordered some blood work through discountedlabs.com, I noticed that the total/free test I selected is by equilibrium analysis, usually when my Dr. orders the free test it's by Direct. Also, is this the same as Equilibrium Dialysis, I did some looking around and that is all I could find. Is this ok and which is preferred? Thanks.

Many do get the direct for free T but equilibrium dialysis is considered the gold standard.

https://www.excelmale.com/forum/sho...a-Interpretation-and-Methodological-Appraisal

 

[madman]

https://www.excelmale.com/forum/sho...ation-Physiological-and-Clinical-Implications

 

[madman]

https://academic.oup.com/view-large/94946853

 

[OMI100]

O.K. MM
You clearly have this down pat
SO for someone like me that is "medical reports" challenged
When would one choose the "Gold Standard" over the simple test?
I would guess that there must be some type of discriminator that would point to the "Gold Standard" such as too low T or too high T, or some medical condition where you want the MOST accurate reading???

 

[madman]

O.K. MM
You clearly have this down pat
SO for someone like me that is "medical reports" challenged
When would one choose the "Gold Standard" over the simple test?
I would guess that there must be some type of discriminator that would point to the "Gold Standard" such as too low T or too high T, or some medical condition where you want the MOST accurate reading???

As stated in the update 2018 An Endocrine Society Clinical Practice Guideline

Regarding Total Testosterone

- TT concentrations are measured using radioimmunoassay, immunometric assays, or liquid chromatography-tandem mass spectrometry
- there is considerable interassay and interlaboratory variability in TT measurements

- similar large interassay and interlaboratory variability occurs with FT measurements

- the variability in T measurements is partly due to calibrator differences and to biotin interference in some immunoassays
- since 2010, the CDC has provided an accuracy-based standardization program for T (CDC Hormone Standardization Program for Testosterone)
- although several commercial laboratories, some assay manufacturers, and some academic laboratories are now CDC certified, most T immunoassay kit manufacturers and local hospital-based laboratories have not been certified

* Liquid chromatography-tandem mass spectrometry assays for TT generally offer higher concentration of specifity, sensitivity, and precision (especially in the low range) than do most immunoassays

- clinicians should ideally measure TT using a CDC-certified assay or an assay verified by an accuracy-based external quality control program

Regarding TT the liquid chromatography-tandem mass spectrometry assay is considered the GOLD STANDARD



Regarding Free Testosterone

- local laboratories usually do not have accurate and reliable assays for FT measurement
- therefore, clinicians should use a reliable reference laboratory for these tests

- clinicians should measure FT using the equilibrium dialysis method performed under standardized conditions
- if equilibrium dialysis is not available for measuring FT, clinicians should estimate FT concentration using a formula that accurately calculates FT concentrations using TT, SHBG, and albumin concentrations
- the estimates of FT, regardless of the formula used, are predicted upon accurate measurements of TT, SHBG, and albumin

- recent studies using modern biophysical techniques suggests that SHBG circulates as a dimer and that binding of T to SHBG is a multistep process that involves an allosteric interaction between the two binding sites on the SHBG dimer, such that the affinities of the two sites are not equivalent

- estimates of FT that use an allosteric model provide close approximations of measures using equilibrium dialysis
- furhter investigation is needed to determine the preferred method for routinely estimating FT concentrations in clinical populations

- FT measurements by direct tracer analog immunoassays are frequently available in local and some reference laboratories, but these direct immunoassays are inaccurate and should not be used

- a major difficulty in determining FT concentrations is the lack of standardization regarding FT assays, resulting in variability in the lower limit of the reference ranges quoted by different laboratories

- given the uncertainties in the methods of calculations and variations in reference intervals, laboratories are encouraged to establish their own specific reference ranges for FT measurement by equlibrium dialysis and calculated FT (preferably calculated against the equilibrium dialysis method)

Regarding FT the equilibrium dialysis method is considered the GOLD STANDARD

 

[madman]

O.K. MM
You clearly have this down pat
SO for someone like me that is "medical reports" challenged
When would one choose the "Gold Standard" over the simple test?
I would guess that there must be some type of discriminator that would point to the "Gold Standard" such as too low T or too high T, or some medical condition where you want the MOST accurate reading???

As stated in the 2018 Evaluation and Management of Testosterone Deficiency: AUA Guideline

- testosterone assays are plagued by variability in results
- this variability is expressed as a coefficient of variation (CV), which is a measure of precision
- in order to express this precision of assay test results, two measures of the CV are typically reported; the inter-assay CV and the intra-assay CV

- inter-assay CV measures the agreement between tests using the same method of measurement on identical samples, in the same laboratory, by the same operator using the same equipment within a short interval time

- intra-assay CV is the degree of variation between repeated measurements of the same sample under different conditions

- these parameters are calculated by analyzing normal and abnormal control specimens that have known values of the substance being measured

- the differences in testosterone methodologies have led to considerable effort by a variety of parties including The Centers for Disease Control (CDC) and the College of American Pathologists towards harmonization of assays https://www.cdc.gov/labstandards/hs_standardization.html

- part of this effort includes the availability of serum-based reference material from pooled sera available from the National Institute for Standards and Technology for testosterone and a hormone standardization program using liquid-chromotography/mass spectrometry (LCMS) offered by CDC https://www.cdc.gov/labstandards/pdf/hs/Testosterone_Protocol.pdf

- laboratories that perform testosterone assays that have a CV that falls within +/- 6.4% of samples tested by the CDC (with testosterone values ranging from 2.5-1000 ng/dl) are CERTIFIED

* the names of these laboratories are available on the CDC website https://www.cdc.gov/labstandards/pdf/hs/CDC_Certified_Testosterone_Procedures-508.pdf

 

[madman]

O.K. MM
You clearly have this down pat
SO for someone like me that is "medical reports" challenged
When would one choose the "Gold Standard" over the simple test?
I would guess that there must be some type of discriminator that would point to the "Gold Standard" such as too low T or too high T, or some medical condition where you want the MOST accurate reading???

When diagnosing a patient for hypogonadism and certain medical conditions especially when testosterone is at very low concentrations than liquid chromatography-tandem mass spectrometry (LCMS) should be used to measure TT levels to maximize accuracy and limit CV between tests

If a man has low-normal TT (total t) or average-higher TT levels along with high SHBG and is presenting symptoms of low t than equilibrium dialysis should be used to measure FT (free t)

*As stated in the 2018 AUA guidelines although direct measurement of FT has a generally good correlation with equilibrium dialysis, it is not reliable because of high CV (co-efficient variation)

 

[OMI100]

When diagnosing a patient for hypogonadism and certain medical conditions especially when testosterone is at very low concentrations than liquid chromatography-tandem mass spectrometry (LCMS) should be used to measure TT levels to maximize accuracy and limit CV between tests

If a man has low-normal TT (total t) or average-higher TT levels along with high SHBG and is presenting symptoms of low t than equilibrium dialysis should be used to measure FT (free t)

*As stated in the 2018 AUA guidelines although direct measurement of FT has a generally good correlation with equilibrium dialysis, it is not reliable because of high CV (co-efficient variation)

MM My head hurts now
Then as I read, a quick down and dirty CK, the cheap one, will suffice BUT if one falls into the situations mentioned one might need to spend the extra $$$$ to get a more accurate reading.
Or if one does the quick and dirty and has results as noted above, a re-test with the appropriate "Gold Standard" test would be warranted.
You clearly have this stuff done pat
Some of the technical stuff makes my head explode