Unconjugated estriol (uE 3 ) is one of the most important serum markers for prenatal screening. The abnormally low content of uE 3 is used as an indicator of fetal DS (Down syndrome) during the second trimester in pregnant women. In the present study, we developed a time-resolved fluoroimmunoassay to detect uE 3 by employing microtiter plates with pre-captured primary antibodies. E 3 -3-CME-BSA (estriol-3-carboxymethyl ether-bovine serum albumin) conjugates served as labels and Eu 3+ (europium) as the probe for signal detection. The detection limit of this assay was 0.35 nmol L À1 . The within-run and between-run imprecision values for serum control detection were less than 5.0% and 6.0% respectively. The mean recovery was 102.6%. The long-term stability (2-8 C, 15 months) and thermostability (37 C, 10 days) were excellent. The uE 3 concentrations measured by the present assay in 1168 Chinese maternal serum samples correlated well with those obtained by the chemiluminescence immunoassay assay (r ¼ 0.948). The reference range in normal singleton pregnancies in Southern China was established which provided reference data to adjust the uE 3 medians for biochemical screening.

Article in press -uncorrected proof Determination of median levels of the free b subunit of human chorionic gonadotropin in women from mainland China using a new time-resolved fluoroimmunoassay ) chelates only. Methods: We developed a two-site, one-step assay using two monoclonal antibodies (MAbs) against free b subunit and b subunit with Eu 3q chelates as labels. Using the present assay, we evaluated 24,634 normal serum samples in Chinese pregnant women during 8-20 weeks of gestation. Results: The detection limit using this assay was -0.05 ng/mL. The within-run and between-run imprecision was -6.0% and 7.0% using control material. Free b-hCG concentrations measured using the current assay in 999 maternal serum samples correlated well with those obtained by samarium (Sm 3q )-labeled DELFIA free hCGb assay (rs0.987). The medians for 8-20 weeks for maternal serum free b-hCG were higher in the women from mainland China compared to reports from other countries. Conclusions: The present assay is suitable for use in biochemical screening of women in mainland China. Our study on the median concentrations of free b-hCG will help establish reference values that are specific for ethnic populations from the Chinese mainland. These will be useful for studying the importance of ethnic factors in biochemical screening.

Pregnancy-associated plasma protein A (PAPP-A) is an important serum marker for first trimester screening. Its weekly median value varies with ethnicity. A one-step time-resolved fluoroimmunoassay (TRFIA) using two monoclonal antibodies against PAPP-A with Eu(3+) chelates as labels has been developed. Using the assay described here, we evaluated 5,301 normal serum samples from Chinese women at 7-13 weeks of gestation. The detection limit using this assay was 1.2 mIU/L, and the maximum detection range was up to 10,000 mIU/L. The intra-assay and inter-assay coefficients of variation were <3.0% and <5.0%, respectively, and the mean recovery rate was 98.0%. PAPP-A concentrations measured in 516 maternal serum samples correlated well with those obtained by Dissociation-Enhanced Lanthanide Fluorescent Immunoassay (DELFIA) PAPP-A assay (r=0.988, P<0.001). The medians for 7-13 weeks of maternal serum PAPP-A were higher in the women from China compared to reports from other countries. The present assay possesses accuracy and high sensitivity and exhibits great potential for the clinical analysis of PAPP-A. Our investigation on the median concentrations of PAPP-A will help establish reference values that are specific for China and study the importance of ethnic factors in biochemical screening.