Performance Characteristics of the UniCel DxI 800 Immunoassay for the Maternal Serum Quadruple Test, Including Median Values for Each Week of Gestation, in Korean Women

Abstract

Maternal serum prenatal quadruple screening includes tests for alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), unconjugated estriol (uE3), and dimeric inhibin A (DIA). Measurements of maternal serum AFP, uE3, and hCG, as well as maternal age, are widely used in the second trimester for the identification of pregnancies at high risk of Down syndrome [1,2]. The maternal serum mid-trimester triple marker test is also a widely accepted protocol in Korea [3][4][5]. The triple test (AFP, uE3, hCG Background : Maternal serum prenatal quadruple screening includes testing for alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), unconjugated estriol (uE3), and dimeric inhibin A (DIA). We evaluated quadruple screening using an automated platform and looked for any ethnic differences in the median values of each marker.Methods : We measured the concentrations of each quadruple test analyte using the UniCel DxI 800 system (Beckman Coulter, USA) in 788 Korean mid-trimester maternal serum samples and calculated their median values using Benetech software (Benetech, Canada). We also compared the results with those obtained using the Immulite 2000 assay (Siemens Healthcare Diagnostics, USA) or ELISA (DSL, USA) in 442 samples.Results : We obtained mid-trimester median values for each marker. The following are the comparative results for each test using the Immulite 2000 assay or ELISA (x) and the UniCel DxI 800 immunoassay (y): AFP, y=1.10x+0. 01, r=0.925; uE3, y=0.28x+0.24, r=0.885; hCG, r=0.944; and DIA, y=0.86x+15.31, r=0.833. Assay results for each of the four markers showed good correlations. However, significant biases necessitated new median calculations of prenatal risk estimates in all four tests.Conclusions : We established gestational age-specific second-trimester median values for four markers in Korean samples using the UniCel DxI 800 immunoassay system. Despite significant bias, there were good correlations between the results obtained using the UniCel DxI 800 immunoassay and those obtained using the Immulite 2000 assay. (Korean J Lab Med 2010;30:126-32)

Different median levels of serum triple markers in the second trimester of pregnancy in a Thai Ethnic Group

“…When comparing triple marker levels with those in other countries, after correction with gestational age and weight group, the medians of AFP, hCG, and uE3 levels in the northern part of Thailand are somewhat higher, though in some weight subgroups of AFP the levels are similar. This observation was different from that reported in a Korean study, 4 in which the median hCG and AFP were somewhat higher while the uE3 levels were similar, signifying that specific groups in Asia, either Oriental or south or southeast Asia, like Thailand, should have their own databases. Though several studies have observed that these medians values are higher among an Asian population relative to other ethnicities, those Western studies included only small sample sizes of Asian groups in their studies and mixed subgroups of Asian populations.…”

“…However, normal reference ranges for specific groups of pregnancies should be developed for their own population. Several studies demonstrate that ethnicity strongly affects concentrations of these markers 3–5 . For example, serum hCG values are higher in black pregnant women, though the magnitude of the difference varies considerably 6–8 .…”

Evaluation of the UniCel™ DxI 800 Immunoassay Analyzer in Measuring Five Tumor Markers

“…The results on the linearity and imprecision of the assays by DxI were highly acceptable and in accordance with previous reports 12,14-16,21-23. In addition, we compared the results from DxI for CEA, AFP, and CA 125 with those measured by Centaur, and for CA 15-3 and CA 19-9 with those measured by ECi, as our laboratory currently uses Centaur and ECi, which were intended to be replaced with DxI, for assaying these respective tumor markers.…”

“…The concordance between assay systems can vary according to the evaluated tumor markers and researchers 12,15,16,21,22. Therefore, even though the results, on average, agreed fairly well across the assays, when replacing tumor marker assays for clinical use, parallel tests by old and new methods are recommended to establish a new baseline in the management of patients.…”

“…The UniCel™ DxI 800 Access Immunoassay System (DxI) is an automated instrument that can handle a large volume of various test items with high throughput, and only a few studies have tested the performance characteristics of this analyzer so far 14-16. In this study, we aimed to evaluate the analytical performance of this immunoassay analyzer in measuring five tumor markers (AFP, CEA, CA 15-3, CA 125, and CA 19-9).…”