I would prefer the Equilibrium Dialysis over any.....yes most are using the direct immunoassay, the calculated Vermeulen method is online for free
Most are getting the Direct analog enzyme immunoassay (EIA) :
144980: Testosterone, Free, Direct | LabCorp
Instead of Equilibrium Dialysis which is considered the gold standard regading accuracy of Free Testosterone levels : 500726: Testosterone, Free, Mass Spectrometry... | LabCorp
