Clinical and analytical evaluation of an immunoradiometric assay for corticotropin.
We evaluated a new IRMA developed commercially for the measurement of corticotropin (ACTH) in human plasma. The assay involves purified polyclonal goat capture antibodies specific for ACTH 26-39 and an 125I-labeled monoclonal signal antibody specific for ACTH 1-17. CVs for intraassay and total precision at ACTH concentrations between 9 and 801 ng/L ranged from 2.5% to 4.7% and from 3.3% to 9.3%, respectively, with an assay detection limit of 1.7 ng/L. The reference interval determined for adults with the new method (16-52 ng/L) differed significantly (P < 0.05) from that for an established ACTH IRMA (9-54 ng/L). Method comparison with clinical samples (n = 179) revealed a correlation coefficient of 0.970 and a best-fit equation of y (new IRMA) = (1.011 +/- 0.019)x + (4.17 +/- 3.31) with Sylx = 40.2. Both methods showed equivalent clinical sensitivity in evaluating Cushing disease, adrenal tumors, ectopic ACTH-producing tumors, hypopituitarism, steroid suppression, surgical adrenalectomy, Nelson syndrome, Addison disease, and corticotropin-releasing hormone stimulation. We conclude that the new IRMA is technically simple to perform and provides a specific and sensitive method for evaluating of adrenocortical function.
Rosano
T G
TG
Department of Pathology, Albany Medical Center, NY 12208, USA.
Demers
L M
LM
Hillam
R
R
Dybas
M T
MT
Leinung
M
M
D000303:Adrenal Cortex Diseases / Q000097:blood; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000328:Adult; D000911:Antibodies, Monoclonal; D001800:Blood Specimen Collection / Q000295:instrumentation; D005260:Female; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D000324:Adrenocorticotropic Hormone