Testing Testosterone

I'm not usually fixated on testosterone but as I mentioned yesterday, some of the confusion in defining hypogonadism is in deciding how low is low.  This is especially problematic when one can obtain widely disparate values from any given sample.  Thus, the Endocrine Society and the Centers for Disease Control & Prevention brought together the various stakeholders earlier this year to develop a plan for standardization.  They published a statement last month outlining their plans to achieve standardization.

For instance, should you choose Quest Diagnostics, your total testosterone is usually assayed via liquid chromatography tandem mass spectrometry (LC/MS/MS), regardless of which test code you choose.  However, free testosterone can be calculated from equilibrium dialysis or based upon constants for binding to sex hormone binding globulin.  Presumably, bio-available testosterone would be calculated based upon binding to sex hormone binding globulin and albumin.  Or vice versa.  But you get the point.  As a clinician (and not a pathologist), I need to be sure that I (or my staff) order the right (same) test each time so that we can compare apples to apples. 

This doesn't even take into account that LabCorp uses immunochemiluminometric assay (ICMA) to measure total testosterone and equilibrium ultrafiltration for free testosterone under one test code while they use LC/MS/MS and direct radioimmunoassay under another.  They even go on to discuss the debate amongst researchers as to the variance in results dependent upon methodology and even population used for reference.

The point of this for you and me is to realize that, at least for now, our patients need to get their testosterone levels checked at the same laboratory facility using the same technique each time for comparability.  Only then can you determine if they are truly hypogonadal and whether your therapeutic regimen is making a difference.