Plasma 21-deoxycortisol: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunossay using (125)iodine

• Published in: The Journal of steroid biochemistry and molecular biology Vol. 72; no. 1-2; p. 55
• Main Authors: Fiet, J, Boudi, A, Giton, F, Villette, J M, Boudou, P, Soliman, H, Morineau, G, Galons, H
• Format: Journal Article
• Language: English
• Published: England 01.01.2000
• Subjects: Adrenal Hyperplasia, Congenital; Adult; Age of Onset; Biotinylation; Calibration; Cortodoxone - blood; Cortodoxone - immunology; Cross Reactions - immunology; Cross-Linking Reagents; Europium - metabolism; Female; Fluorescence; Fluoroimmunoassay - methods; Humans; Immune Sera - immunology; Iodine Radioisotopes; Male; Menstrual Cycle; Radioimmunoassay - methods; Reproducibility of Results; Sensitivity and Specificity; Streptavidin - metabolism; Time Factors
• ISSN: 0960-0760
• DOI: 10.1016/S0960-0760(99)00151-X

Plasma 21-deoxycortisol (21DF) is an excellent marker of 21-hydroxylase deficiency. Currently, it is the only marker able to detect heterozygous carriers with 21-hydroxylase deficiency after ACTH stimulation. We have already developed radioimmunoassays for 21DF using first tritiated, then 125I-21DF which had a ten-fold higher sensitivity. However, because the lifespan of 125I-21DF is short, the tracer needs to be reprepared every two months and this multiplies the risk of contamination by radioactive 125I vapours. We therefore developed a non-isotopic 21DF assay that uses a 21DF-biotin conjugate with a original bridge, a diaminopropyl arm, linking the steroid to biotin. The 21DF-biotin conjugate was measured by time-resolved fluorescence after adding streptavidin-europium to the microtitration wells. The analytical qualities of this assay were very similar to those of the radioimmunoassay using 125I-21DF as tracer. The results obtained by the two methods, in either normal subjects or patients with 21-hydroxylase deficiency, were virtually the same.