Effect of high throughput RHD typing of fetal DNA in maternal plasma on use of anti-RhD immunoglobulin in RhD negative pregnant women: prospective feasibility study

Abstract

head of red cell immunohaematology, 2 Geoff Daniels, head of molecular diagnostics 1 ABSTRACT Objectives To assess the feasibility of applying a high throughput method, with an automatic robotic technique, for predicting fetal RhD phenotype from fetal DNA in the plasma of RhD negative pregnant women to avoid unnecessary treatment with anti-RhD immunoglobulin. Design Prospective comparison of fetal RHD genotype determined from fetal DNA in maternal plasma with the serologically determined fetal RhD phenotype from cord blood. Setting Antenatal clinics and antenatal testing laboratories in the Midlands and north of England and an international blood group reference laboratory. Participants Pregnant women of known gestation identified as RhD negative by an antenatal testing laboratory. Samples from 1997 women were taken at or before the 28 week antenatal visit. Main outcome measures Detection rate of fetal RhD from maternal plasma, error rate, false positive rate, and the odds of being affected given a positive result. Results Serologically determined RhD phenotypes were obtained from 1869 cord blood samples. In 95.7% (n=1788) the correct fetal RhD phenotype was predicted by the genotyping tests. In 3.4% (n=64) results were either unobtainable or inconclusive. A false positive result was obtained in 0.8% (14 samples), probably because of unexpressed or weakly expressed fetal RHD genes. In only three samples (0.2%) were false negative results obtained. If these results had been applied as a guide to treatment, only 2% of the women would have received anti-RhD unnecessarily, compared with 38% without the genotyping. Conclusions High throughput RHD genotyping of fetuses in all RhD negative women is feasible and would substantially reduce unnecessary administration of antiRhD immunoglobulin to RhD negative pregnant women with an RhD negative fetus.

High-throughput non-invasive prenatal testing for fetal rhesus D status in RhD-negative women not known to be sensitised to the RhD antigen: a systematic review and economic evaluation

“…All the studies were prospective studies and were conducted in European countries. Four studies were conducted in England,12,[17][18][19] three of which were based in Bristol. 12,17,18 The sample size (number of patients/samples analysed) of studies ranged from 282 to 18,383 …”

“…Only three studies stated that multiple pregnancies were included. 17,22,23 Multiple pregnancies can pose specific challenges for NIPT (e.g. twin fetuses may have discordant RhD status).…”

“…We conducted sensitivity analyses (SAs) to explore: l the impact of including and excluding undetermined or uninterpretable NIPT results on the pooled test accuracy estimates l test accuracy in UK (Bristol)-based studies 12,17,18 only.…”

“…After initial screening of titles and abstracts, 227 were considered to be potentially relevant and were ordered for full-text paper screening. In total, eight studies 12,[17][18][19][20][21][22][23] were included in the diagnostic review of high-throughput NIPT, seven studies 18,20,22,[24][25][26][27] were included in the clinical effectiveness review and 12 studies 13,17,18,[20][21][22][23][24][25][26][27][28] were included in the review of implementation of high-throughput NIPT (with some overlap between studies). Figure 1 shows a flow diagram outlining the screening process with reasons for exclusion of full-text papers.…”

High throughput non-invasive determination of foetal Rhesus D status using automated extraction of cell-free foetal DNA in maternal plasma and mass spectrometry

“…This development can greatly assist with the screening and monitoring of pregnancies at risk for haemolytic disease of the foetus and newborn (HDN), and also reduce the health care costs by avoiding unnecessary prophylactic treatment in those cases where the foetus is RHD negative [7].…”