RESUMEN
We share our experience in the development of immunoradiometric assay (IRMA) for gonadotropins, FSH and LH using common tracer concept. Commercially procured, monoclonal antibody against 'common epitope' of FSH and LH was radiolabeled and epitope specific monoclonal antibody against ß-subunit of FSH and LH was chemically immobilized and used as a capture system. In an inclusive assay procedure developed, 100 µl of respective standard and specific capture antibody was incubated with 100 µl common tracer, for 3 h at RT with shaking. Results of validation tests confirmed the clinical utility of the developed procedure with adequate sensitivity of 1.0 mIU/ml, acceptable precision (imprecision CV ≤ 10%), minimal cross-reaction.
RESUMEN
This paper describes the use of avidin-biotin interaction as an affinity system, wherein avidin immobilized magnetizable particles (cellulose) are used as a common separation system in immunoradiometric assay (IRMA) for hormones of the human reproductive system, human follicle stimulating hormone (FSH), and luteinizing hormone (LH). Biotinylated probe was prepared by biotinylation of specific monoclonal antibody for respective antigen using the caproyl derivative of biotin N-hydroxysuccinimide. The detector antibody for the respective antigen was radiolabelled with 125I by a chloramine-T oxidation method and purified by gel filtration. In the IRMA procedure, standard/sample, respective biotinylated, and radiolabelled antibody as a single reagent, and avidin solid phase were added simultaneously to the assay tubes. After incubation for 3 h with shaking, the bound complex was quantitated for its radioactivity associated with the common avidin solid phase. Results showed that the developed assay protocol is applicable to IRMA of FSH and LH with good precision (intra and inter assay CV less than 8% and 11%, respectively), good assay range (0-200 mIU/mL) and analytical recovery (87-110%). The assay could detect 0.5 mIU/mL and 0.9 mIU/mL of FSH and LH, respectively, and showed good correlation with commercially available kits (FSH y = 0.98x + 0.21 and LH y = 0.99x + 0.18).