Evaluation of efficiencies of MCV, HbH inclusion body test and Gap-PCR in the screening of α-thalassemia: A case study of Lampang Hospital

Abstract

α-thalassemia is characterized by quantitive abnormality of α-globin chain commonly occur in Thailand. Heterozygote of α-thalassemia is clinically asymtomatic, but with modest alteration of hematologic parameters. This report aimed to evaluate the routine thalassemia screening methods (MCV, HbH inclusion bodies; HbH-IB) in diagnosis of α-thalassemia diagnosis and to determine whether the single molecular protocol was able to detect the molecular defect causing α-thalassemia in Thais. The study was conducted in 29 students of Lampang Sport School. Full blood count was analyzed by using automated blood cell analyzer. HbH-IB was determined after incubating blood sample in 1% Brilliant Cresyl Blue in 37 ^OC waterbath for 1 hour. Hb identification was performed by LPLC technique. The results showed that all samples analyzed were non-anemic with hemoglobin concentration ranging 11.0-14.6 g/dL, normal Hb typing with normal HbA2 level (1.9-3.3 %) and lower-than-80 fL MCV value. Four samples were positive for HbH-IB. Based on these results, all samples were initially categorized to be α-thalassemia heterozygote. However, after Gap-PCR analysis for α-thalassemia 1, 5 samples with MCV lower than 70 fL were positive and the other 24 were negative. The fingding in this study indicated that the thalassemia screening parameters including MCV, HbH-IB and HbA2 level routinely employed in most routine laboratories might not be of sufficient capability to detect α-thalassemia heterozygote. The additional molecular analysis was required to complete the diagnostic process. This study also indicated that the molecular background of α-thalassemia in Thais is more heterogeneous and only the Gap-PCR for SEA deletion could not cover all the causative molecular defects causing α-thalassemia. Bull Chiang Mai Assoc Med Sci 2009; 42: 94-101.