Red Cell Exchange Transfusion in Sickle Cell Anaemia Patients at the University College Hospital, Ibadan, Nigeria

Abstract

Level of HbA2 more than 4% is the reliable parameter to identify β-thalassemia carrier. However, in some cases the level is not typically increased hence leading to diagnostic dilemma. Thus the objectives of this study were to evaluate the existence of β-thalassemia among borderline HbA2 sample. Out of 11,790 samples received for thalassemia screening, 405 (3.4%) were found to have borderline HbA2 level. Out of this, 117(28.9%) samples were selected by simple random sampling for PCR. Multiplex ARMS-PCR was used to detect β-globin gene mutation and multiplex gap PCR for α-globin genes deletion. The result revealed 36 (30.8%) had β-globin gene mutations, 8 (6.8%) had α-globin gene deletions and 1 (0.9%) had coexistence of α and β-globin gene defects.The commonest gene mutation detected were CD 19 (A-G), detected from 17 (45.9%) samples, followed by 9 (24.3%) with IVS 1-1 (G-A) mutation, 5 (13.5%) with Poly A mutation and 1 (2.7%) showed CAP +1 (A-C) mutation. Two samples (5.4%) showed mutations of Poly A and CD19, 2 (5.4%) showed mutation of IVS 1-1 and CD 19 while 1 (2.7%) showed IVS 1-5 and CD 19 mutations. This study showed 10 (27.0%) positive molecular results even though the HbA2 level was at only 3.0%. There was significant number of people with HbA2 between 3.0% and 3.9% and confirmed as thalassemia carriers by PCR. This data may suggest the level of HbA2 need to be revised to ensure the success of thalassemia screening programme in our population.