Comparison of specific immunoassays for detection of the beta-core human chorionic gonadotrophin fragment in body fluids.
We have validated two new methods, one radioimmunoassay (RIA) and one immunoradiometric assay (IRMA), for the detection of beta-core hCG fragment (beta C-hCG) in body fluids. In addition, we have compared their performance with two other assays designed for beta C-hCG quantification. The RIA uses a rabbit polyclonal antibody raised against pure beta C-hCG which has a high affinity constant, is sensitive to 5 pmol/l, and has significant cross-reaction only with the free beta LH subunit. The IRMA, designed in a liquid phase, uses the same polyclonal antibody associated with a 125I-labelled mouse monoclonal antibody (32H2) raised against beta hCG, is sensitive to 1.5 pmol/l, and does not cross-react significantly with any related glycoprotein. Comparison between these two assays and two others previously published was made by measuring beta C-hCG in urine from healthy pregnant women (n = 47) and gave correlation coefficients higher than r = 0.960 with any combination. Analysis of beta C-hCG in urine of non-pregnant subjects (n = 238) showed measurable beta C-hCG in 8.8% (levels ranged from 5 to 34 pmol/l) with the IRMA and 88.3% with the RIA (n = 30; ranging from 28.4 to 228 pmol/l) (P = 0.05). We concluded that, despite different affinities of the antibody involved and different cross-reactivities with related glycoproteins, the four assays we examined may be equally employed to detect beta C-hCG in pregnancy urine. However, the IRMA appears to be more appropriate for beta C-hCG analysis in non-pregnant individuals, specifically in postmenopausal women because of the high cross-reactivity of the RIA with free beta LH or beta fragments of other glycoproteins. These studies have significance for our understanding of the physiology of beta C-hCG in cancer, pregnancy and after the menopause.
D000906:Antibodies / Q000302:isolation & purification; D001826:Body Fluids / Q000737:chemistry*; D006063:Chorionic Gonadotropin / Q000032:analysis* / Q000276:immunology / Q000652:urine; D018997:Chorionic Gonadotropin, beta Subunit, Human; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D015592:Immunoradiometric Assay; D010446:Peptide Fragments / Q000032:analysis* / Q000276:immunology / Q000652:urine; D011247:Pregnancy; D011863:Radioimmunoassay
D000906:Antibodies; D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D010446:Peptide Fragments