engleski

FREE TESTOSTERONE – ULTRAFILTRATION VS CALCULATED RESULTS

Background Testosterone circulates in the bloodstream as protein-bound and free form. Only the free testosterone (fT) is thought to be the biologically active component. Several mathematical calculations are routinely used for its assessment, because a reference method is time-consuming and unsuitable for routine. Previously, comparing the two published algorithms for calculating fT, we obtained results disagreement only among men population. The purpose of this study was to compare calculated fT results with those measured using centrifugal ultrafiltration method. Methods As a part of the hormonal status evaluation we analyzed fT in 20 males (mean age 35 years). Serum samples were collected according to a standard operating procedure using a blood activator tubes (Becton- Dickinson, Eysins, Switzerland). Testosterone and sex hormone- binding globulin were measured using chemiluminiscent microparticle immunoassay on ARCHITECT i1000SR (Abbott Diagnostics, Lake Forest, IL, USA), while albumin was determined using the Beckman Coulter AU480 (Beckman Coulter Inc., Brea, CA, USA) analyzer. For calculating fT two different published algorithms (Vermeulen eta al. and Ly et al.) were used, whereupon results were compared with concentrations obtained after centrifugal ultrafiltration using Centrifree ultrafiltration devices (EMD Millipore Corporation, Billerica, MA, USA) according to the manufacturer protocol. Statistical analysis was conducted by MedCalc for Windows, version 12.4.0 (MedCalc Software, Mariakerke, Belgium). Results There was statistically significant difference in fT median values obtained by different approaches (Kruskal-Wallis test: 0.230 nmol/L after ultrafiltration vs calculated fT 0.740 nmol/L and 0.505 nmol/L ; P<0.001). However, a very strong correlation between fT values measured after centrifugal ultrafiltration and those obtained by one of the used mathematical algorithm was achieved (r=0.896, P<0.001). Conclusion Results demonstrated that used algorithms are in strong disagreement with the method of centrifugal ultrafiltration for determination of fT. Since centrifugal ultrafiltration procedure is relatively simple and available, it could be a good choice for accurate measurement of fT.

free testosterone, ultrafiltration, calculated results

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