Document Type: Original Article
Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
Background: Quantification of fetal red blood cells (RBCs) in maternal blood is of great importance to calculate appropriate dose of post-deliver anti D immunoglobulin in a rhesus D (RhD)-negative woman.
Objective: The aim of this study is to evaluate a direct immunofluorescence flow cytometry technique in artificial and clinical samples and compared it to the Kleihauer-Betke test (KBT).
Methods: This study was a prospective cohort design. Blood samples from 26 pregnant women who gave birth to RhD positive babies were tested using direct immunofluorescence flow cytometry and KBT techniques to determine the amount of FMH in the maternal circulation. The zone of D-positive cells was identified employing artificial samples including 0.3%, 0.6%, 1%, 1.5%, 2%, 5%, 10%, and 50% of D-positive fetal cells in D-negative maternal cells.
Results: Analysis of 26 clinical samples for FMH showed consistent quantification with the flow cytometry and Kleihauer techniques. Although a good correlation was found between the KBT and flow cytometry results, in artificial samples containing more than 2% of fetal RhD positive cells, the flow cytometry results were closer to theoretical percentages. In a patient with FMH >4 mL, the FMH and consequently the required vial of Ig were overestimated using KBT.
Conclusion: Most of the FMH calculated could have been neutralized by doses less than 625 IU, whereas the routine dose in Iran is more than double that amount (1500 IU). This achievement demonstrates that adjusting between the RhD immune globulin (RhDIg) dose and FMH size is inevitable.