Ebru Dündar Yenilmez

By Ebru Dündar Yenilmez and Abdullah Tuli

Hemoglobin disorders such as thalassemias and sickle cell anemias can be avoided by detecting carriers, ensuring genetic counseling and prenatal diagnosis. Nowadays Chorionic villus sampling (CVS amniocentesis, and cordocentesis are still the most widely used invasive sampling methods for prenatal diagnosis of the fetus. These traditional methods are associated with a risk of fetal loss. The revelation of cell-free fetal DNA (cffDNA) in maternal plasma and serum provides the opportunity of noninvasive prenatal diagnosis (NIPD). Different encouraging clinical applications have arose such as noninvasive identification of fetal sexing, fetal Rhesus D, and the determination of the paternal alleles in maternal plasma. The determination of the presence or absence of paternally inherited alleles in maternal plasma of sickle cell disease (SCD) and β-thalassemia would allow the diagnosis of autosomal dominant diseases or the exclusion of autosomal recessive diseases of the fetuses, respectively. prenatal diagnosis of genetic diseases. Analysis of cffDNA in maternal plasma for NIPD has the advantage of being safer versus the invasive methods. Different technologies were used since the discovery of cffDNA for NIPD—especially high-resolution melting (HRM) analysis is one of those methods. Genotyping can be done with HRM without using labeled probes and more complex regions can be analyzed with unlabeled hybridization probes. High-resolution melting is a rapid and useful method to detect paternal alleles for the NIPD of SCD and thalassemias when the fetus has a risk for double heterozygote.

Part of the book: Sickle Cell Disease

By Ebru Dündar Yenilmez and Abdullah Tuli

Anemia is a major cause of morbidity and mortality worldwide and can be defined as a decreased quantity of circulating red blood cells (RBCs). The epidemiological studies suggested that one-third of the world’s population is affected with anemia. Anemia is not a disease, but it is instead the sign of an underlying basic pathological process. However, the sign may function as a compass in the search for the cause. Therefore, the prediagnosis revealed by thorough investigation of this sign should be supported by laboratory parameters according to the underlying pathological process. We expect that this review will provide guidance to clinicians with findings and laboratory tests that can be followed from the initial stage in the anemia search.

Part of the book: Current Topics in Anemia

By Abdullah Tuli and Ebru Dündar Yenilmez

Thalassemia is a significant health problem worldwide. There are two main classifications, α- and β-thalassemias, which are usually caused by the defective synthesis of the α-globin, and which are commonly caused by different mutations of the β-globin chain. Different hemoglobin mutations have been identified to date. Thalassemias can result in profound anemia from early life and, if not treated with regular blood transfusions, can lead to death in the first year. Prenatal diagnosis of thalassemia is the essential part of preventive medicine and is currently dependent on the use of invasive diagnostic tests within the first 2 months of pregnancy. These diagnostic techniques carry a small but significant risk of fetal loss up to 1%. Molecular diagnostic methods have been developed for genotyping thalassemias based on PCR techniques and high-throughput technologies. Noninvasive tests using cell-free DNA (cfDNA) from a maternal blood sample is also an alternative method, thus eliminating the risk of miscarriage. This chapter summarizes the current invasive approaches and the noninvasive methods using cell-free fetal DNA as new molecular diagnostic methods for genotypic diagnosis of thalassemia in clinical practice. Prevention strategies that encompass carrier screening, genetic counseling, and prenatal diagnosis are discussed.

Part of the book: Thalassemia and Other Hemolytic Anemias

By Ebru Dündar Yenilmez, Umut Kökbaş and Abdullah Tuli

Prenatal detection of the fetal RHD status in early stage of pregnancy is observed to be useful in the management of RhD incompatibility to identify fetuses at risk of hemolytic disease. The routine use of antenatal and postnatal anti-D prophylaxis reduces the incidence of hemolytic disease of the fetus and newborn. Cell-free fetal DNA in maternal plasma is in use today for routine genotyping fetal RHD status. Fetal RhD antigens can be detected in the blood of RhD-negative pregnant women using a nanopolymer-coated biosensor and could be an alternative method for medical diagnosis. We detected RhD-positive fetal antibodies with biosensor in maternal blood of RhD-negative mothers. The electrochemical measurements were performed on a PalmSens potentiostat and corundum ceramic-based screen-printed gold electrode. The demonstrated method has a different view for the detection of fetal RhD status in early pregnancy. The biosensor technology is useful and can be carried out rapidly in clinical diagnosis. Biosensors are also reproducible methods which give results quickly compared to noninvasive fetal RHD genotyping with real-time PCR-based techniques. We suggest that this method could become an alternative part of fetal RHD genotyping from maternal plasma as a prenatal screening in the management of RhD incompatibility.

Part of the book: Blood Groups