Measurement of plasma free steroids by direct radioimmunoassay of ultrafiltrate in association with the monitoring of free components with [14C]glucose

Clin Chim Acta. 1991 Aug 15;200(1):13-22. doi: 10.1016/0009-8981(91)90329-b.


We describe a modified method of centrifugal ultrafiltration using the Grace MPS-3 device for the measurement of plasma free (unbound) steroids (cortisol, testosterone, estradiol, and prednisolone). Plasma was incubated with [14C]glucose to monitor the movement of free components, applied to the MPS-3 and centrifuged. Steroid concentration of ultrafiltrate was directly measured by radioimmunoassay, and multiplied by the ratio of [14C]glucose count (dpm) in plasma to [14C]glucose count (dpm) in ultrafiltrate. The data by this method correlated well with those obtained by equilibrium dialysis. Our results of free steroid in healthy volunteers and patients with various diseases were comparable with the previously reported values. This procedure showed the advantages of small sample volume, rapid separation and the ability to process a large number of samples in a single run.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Blood Glucose / analysis*
  • Dialysis
  • Endocrine System Diseases / blood*
  • Estradiol / blood
  • Female
  • Humans
  • Hydrocortisone / blood
  • Male
  • Middle Aged
  • Prednisolone / blood
  • Pregnancy / blood*
  • Radioimmunoassay
  • Steroids / blood*
  • Testosterone / blood
  • Ultrafiltration


  • Blood Glucose
  • Steroids
  • Testosterone
  • Estradiol
  • Prednisolone
  • Hydrocortisone