Since 1956, is know that sickle cell disease is the result of the replacement of glutamic acid with valine in the 6th position of the hemoglobin Hb ?-chain. Sickle cell disease is among the commonest genetic blood disorders characterized by abnormal formation of long polymers due to hydrophobic interactions between the valine in the adjacent HbS molecule. These polymers change red blood cell shape from normal spherical biconcave disc to the characteristic sickle shape, leading to erythrocyte rigidity. This significantly influences their flexibility leading to their early death, prevent normal blood flow and promote vaso-occlusion which may lead to life-threatening complications like stroke, pulmonary hypertension, and acute chest syndrome. Homozygous or heterozygous hemoglobin S (Hb S) co?inherited with either another hemoglobin (Hb) variant (e.
g., Hb C, D?Punjab, O?Arab) or a ??thalassemia mutation results in sickle cell disease (SCD). Disorders of globin chain production, since they are common in the UK, they are considered as an important aspect of public health.
Antenatal screening of sickle cell disorders (SCD) in particular, is extremely important as this type of hemoglobinopathy is common among specific groups of population in the UK and could be a significant health problem, if left underestimated. Ethnic groups with a clinically significant prevalence of SCD are Africans including African-Caribbeans, African-Americans, Black British and any other African ethnicity, Greeks, Southern Italians, Turks, Arabs, and Indians. Diagnosis of hemoglobinopathies is important as it could be part of the preliminary diagnosis or could help to explain a hematological abnormality seen in a blood test like decreased hemoglobin level or small size of red blood cells. Also,it is important as it could identify an abnormality in an early phase of neonatal screening or to spot fetuses at risk of having a hemoglobinopathy and offer the parents informed choice. Furthermore, that screening could allow genetic counseling of future parents.
An already known family history for an inherited disorder could be a significant help towards the diagnosis and justify completely the need of the screening. National Screening Committee (NSC) has already put in place a policy regarding antenatal screening in hemoglobinopathies. The main aim of the screening program is to identify people who do not have a diagnosed medical disorder and appear to be in a good health status that could, however, have a silent or carrier condition which could potentially be genetically transmitted to the offspring. In that case, there should be a preventive strategy from the part of the health professionals who are involved into primary and secondary care, which could offer all the necessary information along with the option of early identification of the condition.
This could lead to early prevention or even early management. NHS Sickle Cell and Thalassemia (SCT) is a screening program which is focused in finding people who carry genetic conditions like hemoglobinopathies. Sickle cell disease is one of those conditions. Screening is offered to specific groups who might have increased risk of having SCD like all pregnant women, future fathers (where antenatal screening shows that the mother is a genetic carrier) and all newborn babies. Pre?conceptual testing should be offered to women who have infertility investigation tests and in those having in vitro fertilization. If a woman is a carrier for a significant hemoglobinopathy, the partner or sperm donor should be tested.
The same applies in case of a donor ovum is to be used. In case of a pregnant woman who was not aware of her condition, antenatal screening is allowing to her medical team to make all the appropriate arrangements on time during her pregnancy. SCD is inherited in an autosomal recessive pattern which means that in case that both parents are carriers, there is 25% risk that the offspring will have the disease in a homozygous state. The optimum time for the initial screening test should be until the 10th week of gestation as that period is the time of rapid growth and huge developmental changes. It also gives the appropriate time to the future parents to have all the necessary screening procedures and have the option to choose whether they wish to terminate the pregnancy or proceed with it. Prenatal diagnosis takes place when both future parents are known carriers and screening tests are performed to the fetus in order to diagnose if it is affected by the disease.
Antenatal screening differs according to the area where the antenatal unit is placed in terms of prevalence. High prevalence area is where the fetal prevalence of SCD is 1.5 per 10 000 pregnancies or higher, while low prevalence area is where the fetal prevalence of SCD is