ASSESSMENT OF THE RELATIONSHIP BETWEEN FOETAL HAEMOGLOBIN LEVELS, TISSUE DESTRUCTION AND DISEASE SEVERITY IN INDIVIDUALS WITH SICKLE CELL ANAEMIA
Sickle-cell Anaemia is a genetic disorder that leads to the production of Sickle haemoglobin, which results in abnormal functions of the red blood cell under hypoxic conditions. The aim of this study was to assess the relationship between Foetal haemoglobin, markers of tissue destruction and disease severity among individuals with sickle cell anaemia. Thirty seven adults with sickle cell anaemia with average age of 26.24±7.32 years were enrolled in this study. Twenty four of them were females while thirteen were males. Participants enrolled were individuals attending clinic at Haematology Department, Ahmadu Bello University Teaching Hospital Zaria who have been diagnosed with Sickle cell anaemia and were confirmed by cellulose acetate electrophoresis. Foetal haemoglobin was assayed using betke’s alkali denaturation method and complete blood count was done using automated haematology analyzer. Lactate dehydrogenase (LDH) activity and bilirubin concentration were determined by spectrophotometric method while disease severity was computed based on the scores obtained from the clinical and haematological data. From our findings, there was a significant difference (P<0.05) in foetal haemoglobin (HbF) levels and LDH activity between individuals in steady state and those in crises condition. Also there was a significant inverse correlation between HbF levels and LDH activity (P= 0.01, r=-0.59) and between LDH activity and disease severity (P=0.01, r=0.42) but there was no significant (P>0.05) relationship between HbF levels & disease severity (P = 0.69, r = -0.07) and HbF levels & bilirubin concentration (P=0.78, r=-0.05). Therefore the present study suggested that HbF level has an inverse relationship with disease severity and tissue destruction. However, disease severity has a direct relationship with tissue destruction.
Sickle cell anaemia (SCA) is a disorder of the Haemoglobin caused by inheritance of a single abnormal haemoglobin (termed sickle haemoglobin- HbS) which results in physical and chemical modifications of the haemoglobin molecule (Damanhouri et al., 2015). Under conditions of low oxygen concentration, the sickle haemoglobin causes the red blood cell to become fragile and prone to rupture. This condition causes the aggregation of haemoglobin (polymerization) and reduces the overall capacity of the haemoglobin to convey oxygen to tissues by impeding free passage of blood in the vessels (vaso-occlusion) to tissues. Increased rupturing of red blood cells leads to anaemia (reduction in number of red blood cells) (Elias et al., 2012; Damanhouri et al., 2015).
Lactate dehydrogenase (LDH), an enzyme of the glycolytic pathway that catalyzes the inter conversion of pyruvate to lactate is found in abundance in all tissues. It consist of five (5) isoenzymes forms classified according to their electrophoretic mobility. The concentration of these isoenzymes varies from one organ to the other, with LDH1 and LDH2 found primarily in RBCs and heart muscle (Ballas, 2013). There is increased level of LDH in the general blood circulation of individuals with SCA. This is due to the increased breakdown of diseased RBCs and other tissues and has been used as a marker of hemolysis and tissue damage. The haemolysis/tissue damage increases further in individuals with Sickle cell anaemia in crises state (Kato et al., 2006; Ballas 2013). Numerous studies have associated SCA individuals with high LDH level to high prevalence of pulmonary hypertension, renal failure and early death (Kato et al., 2013). High LDH observed in this individuals is as a result of haemolysis and tissue destruction (Mehdi et al., 2013; Alzahriet al.,2015). Despite the importance of LDH as a gold standard marker for tissue damage information about LDH in population suffering from SCA in Nigeria is scarce.
SCA studies have shown that individuals with HbF>10% are regarded as having high HbF (Moreira et al., 2015). SCA Individuals with high HbF, like those from eastern Saudi Arabia and India have been found to experience mild clinical complications of the disease (Miller et al., 1986). Foetal hemoglobin is a type of haemoglobin composed of two subunits of α- globin peptide chains, two subunits of γ globin peptides and a heme moieties necessary for this molecule‟s oxygen-carrying capacity. It is the dominant haemoglobin synthesized in the foetus (Sankaran and Orkin, 2013). It is produced by a fraction of RBCs called F-cells that are able to produce HbF alongside other hemoglobins. The F-cells have the advantage of longer life cycle compared to non-F-cells, and the higher the HbF content the longer the life span of the F-cells. The long life span of F-cell is associated with the characteristic of HbF which is able to resist polymerisation caused by sickle haemoglobin (HbS) (Colella and Traina, 2015). This has prompted studies into HbF composition from other regions of the world, with the aim of understanding the role of HbF in ameliorating SCA complications. Although the HbF levels are known in several populations around the world, only few studies have examined HbF level in patients in Nigeria. Knowledge of the HbF levels will be important in assessing the possible impact of introducing disease modifying drugs (DMD) on the individuals with SCA in Nigeria.
SCA is known to exhibit great clinical diversity. Though the same disease, the effect of disease complications vary significantly from one individual to another. The clinical variation at one extreme are a group that may need close care and at the other end, are a group that may not require any care. Classification of individuals into disease severity group can help detect which severity group they belong and respective care given accordingly based on their need (Mpalampa et al., 2012).
Unlike in the developed countries where advancement in technology can be used to identify who will need close attention, in developing countries these equipment’s are not available (Okocha et al., 2015). Because of this and many other factors the rate of morbidity and mortality is still high compared to in the developed world (Adewoyin, 2015). Therefore, this study intends to classify individuals with SCA based on some common clinical data into severity groups, and to find out if there is any relationship between this severity index, HbF level and markers of tissue damage.
1.1. Statement of Research Problem
• Sickle cell anaemia is one of the most common inheritable diseases in Africa. It affects more than 3million people worldwide with about 300,000 births recorded annually (Weatherall, 2010). In Nigeria alone, about 100,000 new births are recorded annually (CDC, 2012).
• It‟s a major cause of morbidity and mortality in the world (Zempsky, 2010). There is no comprehensive data from Africa on the death rate but survival rate is expected to be lower than that from Europe and North America who have a median survival rate of 45-55 years (Serjeant, 2005).
• Despite the numerous studies on SCA worldwide, there is presently no cure for this disease and a means to measure the severity of the disease (Rees et al., 2010).
1.2. Justification of the Study
• Information on the HbF levels, a modulator of disease severity in SCA individuals is scarce in Nigeria. This information if available will provide basis for the use of hydroxy urea to increase the HbF production for the management of SCA.
• Study on the relationship between HbF and markers of tissue damage will provide information on the levels of these markers and the role HbF have on tissue damage.
• Development of a tool that can measure the severity of a disease will help identify individuals likely to develop a severe disease so that close care is given to them.
1.3. Alternative Hypothesis
There is no relationship between levels of foetal haemoglobin, tissue destruction and disease severity among individuals with sickle cell anaemia.
1.4 Research Questions
i. What is the age sex composition of the study population and the level of haematological parameters within Individual with Sickle cell Anaemia?
ii. How do we classify individuals into severity groups and what is the composition of biochemical markers in the different classes of disease severity groups?
iii. What is the concentration of some biochemical markers among individuals with SCA in steady state and those in crises state?
iv. Is there any relationship between foetal haemoglobin levels, markers of tissue destruction and disease severity?
1.5 Aim of the Study
The general aim of this study is to determine the relationship between Foetal Haemoglobin (HbF) level, tissue destruction and disease severity among Individuals with Sickle Cell Anaemia attending Clinic at ABUTH betweenApril to June 2016.
1.6 Specific objectives of the Study
I. To determine the age gender classification of the study population and examine the composition of their haematological parameters.
II. To classify individuals into disease severity groups.
III. To determine and compare the levels of HbF, LDH and bilirubin in individuals with Sickle cell anaemia.
IV. To determine the relationship between disease severity, markers in III above in individuals with SCA.