Plasma 21-deoxycortisol: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunossay using (125)iodine.
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.
Fiet
J
J
Laboratoire d'Hormonologie, Hôpital St. Louis, 75010, Paris, France.
Boudi
A
A
Giton
F
F
Villette
J M
JM
Boudou
P
P
Soliman
H
H
Morineau
G
G
Galons
H
H
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
D003432:Cross-Linking Reagents; D007106:Immune Sera; D007457:Iodine Radioisotopes; D005063:Europium; C003556:21-deoxycortisol; D019809:Streptavidin; D003350:Cortodoxone