Enhancement of the sensitivity of a chemiluminescent immunoassay for estradiol based on hapten heterology

Objective: To develop a highly sensitive chemiluminescent immunoassay (CLIA) that measures the serum estradiol (E2) levels in postmenopausal women. Methods: The previously developed competitive CLIA for E2 consisted of an immobilized antigen and a labeled antibody with an N-functionalized acridinium ester that was modified to enhance its sensitivity. The modifications were changing the immobilized antigen from E2 to its analogues with its expected effect on hapten heterology and selecting optimal incubation conditions. Results: The hapten heterology in which estriol was used as the immobilized antigen instead of E2 enhanced the sensitivity of the CLIA about 3-fold. A low incubation temperature and a long incubation time also effectively increased the sensitivity of the CLIA. The combination of these modifications enhanced sensitivity about 10-fold. The proposed CLIA with a 16 pmol/L detection limit, was about 5-fold more sensitive than commercially available immunoassay kits for E2. Conclusion: The proposed CLIA is sensitive enough to measure serum E2 levels in postmenopausal women.