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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
LabCorp Vs Quest free testosterone lab ranges: Why are they different?
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<blockquote data-quote="sammmy" data-source="post: 189613" data-attributes="member: 38594"><p>Measuring total testosterone is based on recognizing the testosterone molecule and there are relatively reliable lab methods for that, within 'calibration errors'. I never got one value in US an a completely different value in Europe.</p><p></p><p>Measuring free testosterone requires a method to physically separate the free testosterone from the bound testosterone and the dialysis method does that with a semi-permeable membrane. The concentration of free testosterone is vanishingly small and some part of it gets stuck in the dialysis membrane. So in all cases you are measuring some proxy of it, depending on the membrane used, lab/test conditions, methods used to determine amount free testosterone after dialysis etc. It is proxy first because the method of separation free from bound testosterone is not reliable and second because lab methods to measure free testosterone are unreliable at such small concentrations.</p><p></p><p>You can keep arguing semantics but the simple fact remains - total testosterone values have little variability between labs using the same method, while each free testosterone value is valid only in its own test scale because they are impossible to compare between different methods/labs - hence are proxy.</p></blockquote><p></p>
[QUOTE="sammmy, post: 189613, member: 38594"] Measuring total testosterone is based on recognizing the testosterone molecule and there are relatively reliable lab methods for that, within 'calibration errors'. I never got one value in US an a completely different value in Europe. Measuring free testosterone requires a method to physically separate the free testosterone from the bound testosterone and the dialysis method does that with a semi-permeable membrane. The concentration of free testosterone is vanishingly small and some part of it gets stuck in the dialysis membrane. So in all cases you are measuring some proxy of it, depending on the membrane used, lab/test conditions, methods used to determine amount free testosterone after dialysis etc. It is proxy first because the method of separation free from bound testosterone is not reliable and second because lab methods to measure free testosterone are unreliable at such small concentrations. You can keep arguing semantics but the simple fact remains - total testosterone values have little variability between labs using the same method, while each free testosterone value is valid only in its own test scale because they are impossible to compare between different methods/labs - hence are proxy. [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Blood Test Discussion
LabCorp Vs Quest free testosterone lab ranges: Why are they different?
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