The basic type of beta-thalassamia can be detected/ diagnosed in patients or carriers using the following:
- Red blood cell indices
- Peripheral blood smear
- Qualitative and quantities haemoglobin analysis
- Bone marrow examination
- Molecular genetic testing.
Red cell indices
In thalassaemia syndrome, there is general reduction in red blood cell indices (ie microcytic anaemia) though the degree of microcytosis depends on the type of beta-thalassaemia as can be shown in table 1.
Peripheral blood smear
Carriers/Beta –thalassaemia individuals have less secere RBC morphologic changes than affected individuals but the red cells are microcytic and hyprochromic. Erythroblasts are normally not seen.
Homozygous/ affected individuals show RBC morphologic changes such as microcytosis, hypochromic. erythroblasts are normally not seen.
Homozygous/affected individuals show RBC morphologic changes such as microcytosis, hypochromia, anisocytoosis, poikilocytosis (tear-drops, spherocytes, elliptocytes and elongated cells) slight reticulocytosis,basophillic stipplings and nucleated RBC (i.e. erythroblasts). The number of erythroblasts is related to the degree of anaemia and is markedly increased after splenectomy.
Qualitative and Quantitative Analysis
Cellulose-acetate electrophoresis and diethylaminoethyl (DEAE) cellulose (DE-52) microchromatography or high performance liquid chromatography (HPLC) can be used in identification of the amount and type of haemoglobin present. There is usually an elevated level of HbF and HbA2 above normal in Beta –thalassaemic individual. Betke method can also be used in HbF quantification. Therefore, the following hemoglobin types are most relevant in detection of β- thalassaemia.
-Haemoglobin A (HbA): two alpha chains and two globin beta chains (a2 p2)
-Haemoglobin F (HbF): two alpha globin and two gamma globin chains (a2)
-Haemoglobin A2 (HbA2): two alpha globin chains and two delta globin chains (a2δ2).
However, the heamoglobin pattern in β-thalassaemia individuals varies depending on the type of beta-thalassaemia as shown in table 2.
|Heamoglobin||Normal||Affected βo-thalassaemia homozygote||Β+ thal Homozygotes or heterozygote||Carrier β-thal minor|
(Date from Telen and Kaufman, 1999).
Bone marrow Examination
This is usually not necessary for diagnosis of affected individuals (β homozygotes). The bone marrow is extremely cellular, mainly as a result of marked erythroid hyperplasia, with a myeloid/erythroid ratio reversed from the normal (3 or 4) to 0.1 or less.
Molecular Genetic Testing
Commonly occurring mutations of the beta-globin gene are detected by polymerase chain reaction (PCR) based procedure (Vrettou et al., 2003). The most commonly used methods are reverse dot blot analysis or primer-specific amplification, with a set of probes or primers complementary to the most common mutation in the population from which the affected individual originated. If targeted mutation analysis fails to detect the mutation, beta globin gene IDNA sequence analysis can be used to detect mutations in the beta globin gene.
TREATMENT OF BETA-THALASSAEMIC CONDITIONS
Treatment is based on the type of thalassaeamia,
Thalassaemia Minor: - Individuals with Beta-thalassaemia trait does not require treatment because of the fact that only a small part of one of their beta-globin chain is affected, thus the unaffected beta globin chain can adequately perform its physiological function in their haemoglobin molecule.
Thalassaemia Intermedia:- Treatment of individuals with thalassameia intermedia is symptomatic and based on splenectomy and folic acid supplementation. Treatment of extramedullary erythropoietic masses is based on radiotherapy, transfusions, or, in selected cases hydroxyurea. Hydroxyurea also increases globin gamma chains and may have other undefined mechanisms. Because individuals with thalassaemia intermedia may develop iron over load from increased gastrointestinal absorption of iron or from occasional transfusions, chelation therapy is started when the serum feritin concentration exceeds 300µg/L (Origa et al., 2007).
Thalassaemia major: - This can be treated by:
- Transfusion: regular transfusion correct the anaemia, suppress erythropoiesis and inhibit increased gastrointestinal absorption of iron the transfusion regimen is designed to obtain a pre-transfusion Hb concentration of 95-100g/l Transfusion are usually given every 2-3 weeks.
- Bone Marrow Transplantation (BMT):- Bone marrow transplantation from a Human leucocyte antigen-identical person represents an alternative to transitional, transfusion and chelation therapy. At present, BMT remains the only definitive cure for patient with thalassaemia major. If BMT is successful, iron overload may be reduced by repeated phlebotomy, thus eliminating the need for iron chelation. In children that hence no hepatomegally, high liver extent of fibrosis and low iron accumulation, disease-free survival is over 90%. Adults with beta-thalassaemia are at a higher risk for transplant-related toxicity due to an advanced phase of the disease and have a cure rate of 65% with current treatment protocol (Isgro et al., 2010). Chronic graft-versus-host disease (GVHD) of variable severity may occur in 5%-8% of individuals. Affected individuals without matched donors could also benefit from haploid identical mother –to- child transplantation, the results of which appear encouraging (Sodani et al., 2011).
- Cord blood transplantation: Cord blood transplantation from a related donor offers a good probability of a successful cure and is associated with a low risk for graft versus host disease (Pinto and Roberts, 2008). For couples who have already had a child with thalassaemia and who undertake prenatal diagnosis in a subsequent pregnancy, prenatal identification of HLA fetal allows collection of placental blood at delivery and the option of cord blood transplantation to cure the affected child (Orofino et al., 2003).