Genotipagem rhd fetal no plasma materno

Genotipagem RHD fetal no plasma materno

Gregory A. Denomme
Immunohaematology Reference Laboratory, Blood Centre of Wisconsin, Milwaukee, United States of America

Non-invasive genetic tests using foetal DNA in maternal plasma were developed largely to reduce pregnancy loss related to invasive diagnostic tests for the inheritance of foetal genetic and chromosomal abnormalities1. The immediate application in transfusion medicine was to determine the foetal inheritance of RHD among pregnant women alloimmunised to the D antigen. The article by Laura Salvaneschi et al3 in this issue of Blood Transfusion underscores the value of an international approach to validating any diagnostic test used to predict inheritance of foetal RHD. In the past, the foetal risk of anti-D haemolytic disease of the foetus or newborn (HDFN) was determined from amniotic fluid or chorionic villi-derived DNA and PCR-based assays which accurately detected RHD when it was present but carried a specific level of risk of pregnancy loss and transplacental haemorrhage leading to increased antibody titres. Assays were modified to detect variant and nonfunctional RHD alleles as they were characterised4,5. Foetal RHD typing from maternal plasma has benefited from refinements of specific RHD targets that ensure accuracy, which has been adopted by the International Society for Blood Transfusion (ISBT) Working Party on Red Cell Immunogenetics and Blood Group Terminology. The immediate goal of testing foetal RHD in maternal plasma is to avoid the use of invasive procedures to assess the risk of HDFN, with the option of returning alloimmunised pregnant women to their primary care physician when the foetus is predicted to be RhD-negative. The immediate outcome addressed is a reduction of foetal morbidity/ mortality in the management of HDFN. It is particularly noteworthy that Salvaneschi et al chose a validation plan that integrated international standards. Their validation plan incorporated evaluations of the