Determination of free testosterone fraction of human serum by gel bead dialysis.
The gel bead dialysis technique is an application of the steady-state gel filtration method. Preswollen gel beads are used as microdialysers. The gel is incubated for 3.5 h at 22 degrees C with 2.5 mL of serum and 3H-testosterone. During incubation, the equilibrium between free and protein-bound fractions is reached and the concentration of testosterone in the bead dialysate is equal to the free testosterone concentration in the incubation medium surrounding the beads. After incubation, the gel is separated from the medium by using a rigid filter and the radioactivity within the gel is counted. The effect on the assay of serum dilution and incubation time were studied. Within-batch imprecision (CV) was 3% (N = 30) and between-batch imprecision computed from lyophilized quality controls run over a one year-period, was 7%, 13% and 17% for free testosterone fractions (free over total) of 0.043, 0.032 and 0.021 respectively. An excellent correlation between this technique and the equilibrium dialysis method was found (r = 0.944, N = 59). Reference intervals were determined for men, women and pregnant women; mean +/- SD were 0.0216 +/- 0.0067 (N = 20), 0.0106 +/- 0.0020 (N = 20) and 0.0077 +/- 0.0017 (N = 19) respectively. Patients suffering from polycystic ovary syndrome had significantly higher free testosterone ratio (mean of 0.0285 +/- 0.0074, N = 20) than normal females.
Lavoie
R
R
Centre de Recherche, Hôpital Saint-François d'Assise, Quebec, Canada.
Bergeron
J
J
Fruteau de Laclos
B
B
Forest
J C
JC
D000293:Adolescent; D000328:Adult; D002850:Chromatography, Gel; D003956:Dialysis / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008863:Microspheres; D011247:Pregnancy; D015203:Reproducibility of Results; D013696:Temperature; D013739:Testosterone / Q000097:blood*
D013739:Testosterone