Vijian, Divashini
(2023)
Molecular Characterisation of Alpha-Thalassaemia in Patients Investigated for Hypochromic Microcytic Indices in Hospital Universiti Sains Malaysia.
Masters thesis, Universiti Sains Malaysia.
Abstract
Alpha (α)-thalassaemia is a common genetic disorder that affects 5 % of the
worldwide population. Deletional or non-deletional mutations of one or both HBA1
and HBA2 on chromosome 16 cause a reduction/abnormal in the production of α globin
chains, a component of haemoglobin (Hb) which are required for the formation of red
blood cells (RBC). Thus, reduced Hb leads to anaemia. Many genetic mutations in α-
thalassaemia have been discovered, which produced wide spectrum of clinical
manifestation, ranging from asymptomatic to lethal. This study focused on the
characterisation of RBC parameters and molecular based on α-thalassaemia mutations
to determine the prevalence and to describe the RBC parameters based on the
mutations detected. A cross-sectional study involving 136 suspected α-thalassaemia
patients was collected. The DNA extracted from blood samples was subjected to the
multiplex GAP-polymerase chain reaction, multiplex amplification refractory
mutation system polymerase chain reaction (MARMS-PCR), and duplex-polymerase
chain reaction to detect common deletional and non-deletional α mutations,
respectively. Multiplex ligation dependent probe amplification and Sanger sequencing
were performed to detect rare mutations in patients that do not carry any common
mutations. The prevalence of α-thalassaemia in this study was 47.1 %. Thirty-nine
and 1.4 percent of patients were found to have heterozygous and homozygous α-
thalassaemia mutations, respectively, with 6.6 percent being compound heterozygous.
Among the patients, the following genotypes were found: -α3.7/αα (15.4 %), -α4.2/αα (3.7 %), --SEA/αα (7.4 %), αCSα/αα (10.3 %), αAdanaα/αα (0.7 %), αQuong Szeα/αα (1.5 %),
-α3.7/-α3.7 (0.7 %), αCSα/αCSα (0.7 %), -α4.2/αCSα (0.7 %), –SEA/αCSα (1.5 %), –SEA/αQuong
Szeα (0.7 %), -α3.7/αAdanaα (0.7 %), --SEA/-α3.7 (2.2 %) and αCSα/αAdanaα (0.7 %).
Statistical analysis of RBC parameters according to the mutations was performed. A
few indicators, such as Hb (p=0.020), mean corpuscular volume (p=0.008), mean
corpuscular haemoglobin (p=0.018), RBC (p=0.029) and haematocrit (p=0.049),
showed significant changes among patients with deletional mutations, but there were
no significant differences between patients with non-deletional mutations. patients
with single gene deletional and non-deletional mutations shows only significant
differences for HbA2 (p=0.028). A wide range of RBC parameters were observed
among the patients, including those with the same genotypes. Thus, based on RBC
parameters alone, they are not sufficient to describe the specific mutations of α-
thalassaemia.
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