Non-Invasive prenatal diagnosis of fetal rhd blood group status for d negative pregnant women: new structures for clinical management

• Published in: Pathology Vol. 45; p. S94
• Main Authors: Hyland, Catherine A., Millard, Glenda, O’Brien, H., Gibbon, K., Tremellen, Anne, Gardener, Glenn, Flower, Robert
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2013
• ISSN: 0031-3025; 1465-3931
• DOI: 10.1097/01.PAT.0000426983.72422.6c

To report on the accuracy and clinical application of non-invasive prenatal diagnosis for fetal RHD genotyping. Blood samples (n=788) were collected from n=603 non-selected RhD negative pregnant women, gestation age 7–38 weeks (median age 19 weeks). Samples from n = 110 isoimmun-ised D negative pregnant women were referred from across Australia. Cell free fetal DNA was isolated and qPCR used to amplify fetal RHD sequences from exons 4,5 and 10. Test outcomes were measured against cord blood serology. Among the 788 samples the predicted fetal RHD assignment was negative in 292 (37.1%), positive in 485 (61.5%) and inconclusive in 11 (1.4%). Cord blood RhD results for n=758 showed a strong association between genotype and phe-notype (p < 0.001; Fisher’s exact test). Positive predictive value was 99.4% (95%CI 98.6–100%). Negative predictive value was 100%. Among 110 isoimmunised pregnant women, the predicted fetal RHD assignment was negative in 26 (23.6%), positive in 78 and inconclusive in 6. Inconclusives arose from maternal RHD variants. The maternal blood test is safe and accurate for assessing fetal RHD status. It has been used to guide clinical management of isoimmunised D negative pregnant women from across the country.