title: Plasma 21-deoxycortisol: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunossay using (125)iodine.
abstract: 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.
authors.affiliation: Laboratoire d'Hormonologie, Hôpital St. Louis, 75010, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Fiet
authors.forename: A
authors.initials: A
authors.lastname: Boudi
authors.forename: F
authors.initials: F
authors.lastname: Giton
authors.forename: J M
authors.initials: JM
authors.lastname: Villette
authors.forename: P
authors.initials: P
authors.lastname: Boudou
authors.forename: H
authors.initials: H
authors.lastname: Soliman
authors.forename: G
authors.initials: G
authors.lastname: Morineau
authors.forename: H
authors.initials: H
authors.lastname: Galons
mesh_terms: D000312:Adrenal Hyperplasia, Congenital; D000328:Adult; D017668:Age of Onset; D019921:Biotinylation; D002138:Calibration; D003350:Cortodoxone / Q000097:blood* / Q000276:immunology; D003429:Cross Reactions / Q000276:immunology; D003432:Cross-Linking Reagents; D005063:Europium / Q000378:metabolism; D005260:Female; D005453:Fluorescence; D015200:Fluoroimmunoassay / Q000379:methods*; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007457:Iodine Radioisotopes; D008297:Male; D008597:Menstrual Cycle; D011863:Radioimmunoassay / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019809:Streptavidin / Q000378:metabolism; D013997:Time Factors
chemical_list: D003432:Cross-Linking Reagents; D007106:Immune Sera; D007457:Iodine Radioisotopes; D005063:Europium; C003556:21-deoxycortisol; D019809:Streptavidin; D003350:Cortodoxone