Using circulating fetal DNA from maternal blood for prenatal diagnosis of sickle cell disease.

Abstract

The aim of this project is to develop a robust method for non-invasive prenatal diagnosis (NIPD) for sickle cell disease, an autosomal recessive disorder of the red blood cells. This condition is the most common inherited blood disorder in the UK, and has serious life threatening symptoms. We have begun to develop a test that can be used to diagnose sickle cell disease in a fetus from a maternal blood sample taken during early pregnancy. The benefit of using a maternal blood sample for the prenatal diagnosis is that an invasive procedure such as chorionic villus sampling (CVS) or amniocentesis is not required, reducing potential anxiety and risk for the mother, and also reducing costs to the health service. Blood samples were collected from pregnant women who were having a standard of care invasive test for sickle cell disease, and plasma saved prior to cell free DNA extraction. The non-invasive prenatal diagnosis method will rely on a relative haplotype dosage method, where the proportion of DNA fragments containing a particular genotype are counted from next-generation sequencing data. Using a string of genotypes that are linked to the sickle variant will increase the power to accurately diagnose a fetal sickle cell status. Haplotypes (a string of genetic variants that are linked, or inherited together) on which the sickle mutation and the haemoglobin C (HbC) mutation have arisen were defined by using next generation sequencing to genotype SNPs across the beta globin gene locus in 20 families where the parents were sickle or HbC carriers. Three different sickle haplotypes and four different HbC haplotypes were defined. Where this testing will fit into the sickle cell and thalassaemia screening pathway was also considered as part of this project, as this technology has the potential to completely change how antenatal screening is carried out. Audit data from the sickle screening program was analysed to assess the potential position for the non-invasive test within this pathway, and whether it is likely to be both effective in reducing the time taken to make a fetal diagnosis, to bring the diagnosis earlier in the pathway, to be more cost effective, and also to reduce the number of invasive tests needed. The current antenatal screening pathway was analysed and a proposed structure for introduction of the NIPD testing is presented.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	William Newman (Supervisor)