Sensitivity and Specificity of the Identification of Fetal Cells in Maternal Blood by Combined Staining with Antibodies against Beta-, Gamma- and Epsilon-Globin Chains

Abstract

Objectives: Antibodies against fetal and embryonic hemoglobins may identify fetal cells in maternal blood. Both γ- and Ε-globins are used as fetal cell markers. γ-Globin is not fetus specific. So far Ε-globin has been claimed to be fetus specific. In this communication, we compare the specificity of anti-Ε- and anti-γ-globin staining when combined with staining for β-globin. Methods: We applied single and double color immunofluorescent staining techniques in combination with XY chromosome hybridization. The blood sample was taken after chorion villus biopsy at 11 weeks of gestation from a woman carrying a male fetus. Results: By γ-globin staining alone, 21 fetal and 2 maternal nucleated red blood cells (NRBCs) were identified. Only 1 of the 2 maternally derived NRBCs expressed β-globin. By Ε-globin staining, 92 additional fetal NRBCs were identified. Conclusions: Ε-Globin antibody and combined Ε- and γ-globin antibody staining of a blood sample from a pregnant woman at 11 gestational weeks showed higher sensitivity but lower specificity for the fetal origin of erythroblasts with combined compared with separate staining. The final decision of the origin of cells was made by gender determination by FISH. Out of 2 γ-positive maternal cells 1 was β-globin antibody positive, 1 was β-globin negative, indicating that 100% specificity for fetal origin could not be obtained by combining all 3 hemoglobin types. Although only 1 blood sample was tested and only 2 γ-positive maternal NRBCs were identified, the result indicates that β-hemoglobin does not discriminate completely between γ-positive NRBCs of fetal and maternal origin.