Application of an erythroblast scoring system and DNA polymorphism sequence analysis for the gender-independent assessment of fetal cells in maternal blood

Abstract

SEQUENCE ANALYSIS FOR THE GENDER-INDEPENDENT ASSESSMENT OF FETAL CELLS IN MATERNAL BLOOD DONGHYUN CHA, KIARASH KHOSROTEHRANI, DIANA BIANCHI, KIRBY JOHNSON, Pochon University, Obstetrics and Gynecology, Seoul, South Korea, Tufts University, Pediatrics, Boston, Massachusetts, Tufts University, Pediatrics, Obstetrics & Gynecology, Boston, Massachusetts OBJECTIVE: The aim of this study was to determine whether fetal nucleated red blood cells (fNRBCs) could be distinguished from maternal cells in peripheral blood using an erythroblast scoring system based on the unique morphological and hemoglobin staining characteristics of this cell type. Presumptive fNRBCs were further analyzed for the presence of paternally inherited DNA polymorphisms to prove fetal origin. STUDY DESIGN: fNRBCs were isolated by density gradient separation, CD15/ 45 depletion, and gamma hemoglobin positive selection from peripheral blood of nine women following termination of pregnancy for trisomy 21 (4 cases), 18 (1 case), 13 (2 cases), and other genetic abnormalities (2 cases). Candidate fetal NRBCs, based on four discrete morphological and hemoglobin staining criteria, were then subjected to fluorescent PCR amplification of chromosome 21 (D21S1411, D21S11) and chromosome 18 (D18S535) short tandem repeat (STR) DNA polymorphisms. RESULTS: In all cases candidate fetal NRBCs were accurately identified based on morphologic and hemoglobin staining characteristics and confirmed to be fetal in origin based on the presence of shared and non-shared polymorphic DNA alleles when compared to DNA isolated from maternal cells. CONCLUSION: Using the erythroblast scoring system and subsequent analysis of inherited DNA polymorphisms, we were able to distinguish fetal NRBCs from maternal cells and prove fetal origin independent of gender. These results suggest that this novel combined approach to fetal cell isolation and genetic analysis is a promising method for noninvasive prenatal diagnostic applications. Women and Infants’ Hospital, Maternal Fetal Medicine, Providence, Rhode Island, University of North Carolina, Department of Obstetrics and Gynecology, Chapel Hill, North Carolina OBJECTIVE: Vaginal bleeding in the first trimester may result in a disruption in the maternal-fetal interface with subsequent transfer of hormones into the maternal circulation. Elevated maternal serum concentrations of AFP have been observed in the first and second trimester in women with a history of first trimester vaginal bleeding. Our goal was to examine the effect of first trimester vaginal bleeding on first trimester serum levels of PAPP-A, free b-hCG, and nuchal translucency (NT) using a prospectively-collected large database. STUDY DESIGN: Women enrolled in the FASTER trial had a NT measurement and PAPP-A and free b-hCG levels drawn at 10 3/7-13 6/7 weeks. Patients with fetal anomalies, a diagnosis of diabetes prior to becoming pregnant or who conceived with invitro fertilization were excluded from this analysis. Patients were divided into three groups: (1) no bleeding, (2) light bleeding, or (3) heavy bleeding. The log transformed multiples of the medians (MoMs) of NT, PAPPA, and free b-hCG for the three groups were compared using analysis of variance for crude effects and analysis of covariance adjusting for possible confounding variables. For presentation, the results were back transformed to medians in MoMs. RESULTS: The study included 34,548 patients: 29,639 patients without bleeding, 4341 patients with light bleeding, and 547 patients with heavy bleeding. Adjusted medians of the MoMs of the markers are listed in the table. CONCLUSION: First trimester vaginal bleeding does not appear to affect PAPP-A or free b-hCG levels nor does bleeding impact NT measurement in this large study.