What is a premarital check-up?

A premarital check-up is a series of medical consultations carried out by two consenting parties to assess their health, detect and prevent certain diseases and evaluate the risk of transmitting certain hereditary anomalies. In some countries, this is compulsory before marriage, while in others, such as Niger, it is strongly recommended due to the prevalence in the general population of hereditary diseases such as sickle-cell anaemia. 

Sickle cell disease, a red blood cell anomaly: 

Blood, the red liquid that escapes at the slightest skin opening, is a vital biological fluid circulating in so-called blood vessels to transport nutrients, water and oxygen to the body’s tissues. It also collects waste products from these cells for elimination or transport to disposal sites. In the event of an attack by pathogens, it is through the blood that cells specialized in the body’s defence are transported to the site of aggression. Blood is made up of figurative elements (red blood cells, white blood cells and platelets) swimming in a liquid (plasma). Red blood cells, also known as red blood cells or erythrocytes, make up the largest population of figurative blood elements. For example, there are between 600 and 700 red blood cells for every white blood cell. Each hematite contains a protein called haemoglobin, which transports oxygen from the lungs to the tissues and, conversely, eliminates carbon dioxide. 

The genetic anomaly responsible for sickle cell disease is a substitution in the β chain of globin (one of the parts of haemoglobin) where glutamic acid, a negatively charged amino acid, is replaced by valine, a neutral amino acid. This gives rise to diseased haemoglobin (HbS), which, unlike normal haemoglobin (HbA), loses its physicochemical properties, making it insoluble in hypoxia when there is a mismatch between tissue oxygen requirements and supply. Red blood cells become sickle-shaped; they clump together and obstruct blood vessels, creating the ischemia that gives rise to vaso-occlusive crises. 

In addition to this change, the lifespan of this hematuria is shortened, eventually leading to chronic anaemia through accelerated destruction of the mutant red blood cells. 

Transmission from ascendants to descendants: 

The mutated gene responsible for sickle cell disease is recessive and carried on the short arm of chromosome 11, giving rise to an autosomal recessive mode of transmission. With this mode of transmission, sickle cell disease strikes regardless of gender and requires two alleles (HbS-HbS: SS) to manifest itself. When an individual carries a single allele (HbA-HbS: AS), he or she does not manifest the disease. He or she is called a healthy carrier. So, for a child to be sickle-cell anaemic, both parents must possess the mutated gene and pass it on to the child.  

The mutant haemoglobin is revealed by haemoglobin electrophoresis, an examination that separates and studies the different parts of this protein. 

Nigerians are familiar with sickle cell disease:

Its high prevalence, around 25% according to Nigerien experts in the field, makes this one of the best-known diseases in terms of both clinical expression and transmission. Indeed, “hepatitis”, as it is popularly known in Niger, has a high mortality rate before adulthood. Even when they reach adulthood, the lives of sickle cell patients are severely hampered by sporadic painful attacks and prolonged infections requiring hospitalization, which has a psychological and financial impact on parents and other family members. The clinical expression of sickle cell disease is therefore not foreign to the vast majority of the population, and neither is the mode of transmission, which is widely used to explain autosomal recessive inheritance to high-school science students.  As a result, young high-school students are adept at calculating the probability of having a sickle-cell child. The probability is 100% if both parents are sickle-cell carriers; 50% at each birth if one parent is a sickle-cell carrier while the other is a single-allele carrier; and 25% at each birth if both parents are healthy carriers. These latter scenarios, coupled with the age at which young people begin to fall in love, explain the high propensity of young people to be screened for sickle cell anaemia before any serious commitment. 

Conclusion:

Sickle cell anaemia is an autosomal recessive inherited disorder of the red blood cell that can be detected by haemoglobin electrophoresis. Its high prevalence in Niger explains the importance of this test as part of the premarital check-up.