[Cross-reactivity evaluation of improved estradiol (E2) assay reagent based on chemiluminescent enzyme immunoassay]

We evaluated the performance of a newly-improved estradiol(E2) assay reagent (NEW LP-E2-N), which replaces murine monoclonal antibody in the present reagent (LP-E2-N) with sheep monoclonal antibody, since we had experienced discrepant E2 assay results between LP-E2-N and other commercially available E2 assay kits. Several examinations with the new assay reagent indicated a good performance in terms of the limit of quantity, reproducibility (within-run and between-day), dilution linearity, and influence of blood components except hemoglobin. Using analogues and/or metabolites of E2, low or no cross-reactivity has been shown in NEW LP-E2-N: 0.26% with 25 ng/mL of estrone (El), 0.14% with 100 ng/mL of estradiol-3-sulfate, 0.02% with 200 ng/mL of 17α-ethynylestradiol, and less than 0.001% with 100 ng/mL of estriol(E3), estra-17-glucuronide, and estramustine, respectively. Although discrepant results between NEW LP-E2-N and LP-E2-N were observed in 12 samples, including 9 cases under oral hormone therapy, data from these samples were similar to those using 2 commercially available E2 assay kits, Architect and Eclusys, suggesting that the NEW LP E2-N shows adequate clinical efficacy. A correlation study was performed with LP E2-N, Architect, and Eclusys using 149 serum samples obtained from patients and healthy volunteers, and the correlation results were as follows: r = 0.831, y = 0.98x + 40.6 against LP-E2-N, r = 0.991, y = 1.08x + 12.4 against Architect, r = 0.995, y = 0.80x - 3.7 against Eclusys. In conclusion, the NEW LP-E2-N reagent displayed a relatively favorable kit performance except for in the elevation of assay results with hemoglobin, as well as a low cross-reactivity with E2 analogues and/or metabolites.