Impact of the detection of ζ-globin chains and hemoglobin Bart's using immunochromatographic strip tests for α0-thalassemia (--SEA) differential diagnosis

alpha(0)-Thalassemia is an inherited hematological disorder caused by the deletion of alpha-globin genes. The Southeast Asian deletion (--(SEA)) is the most common type of alpha(0)-thalassemia observed in Southeast Asian countries. Regarding WHO health policy, an effective alpha(0)-thalassemia screening strategy is needed to control new severe alpha-thalassemia cases. In this study, a monoclonal antibody panel was used to develop immunochromatographic (IC) strip tests for detecting the Hb Bart's and zeta-globin chain. Among 195 samples, all alpha-thalassemia traits (78-thalassemia-thalassemia (--(SEA)) and 4 alpha(0)-thalassemia (--(THAI))) had low MCV or MCH values. The sensitivity, specificity, PPV and NPV of the IC strip tests for zeta-globin and Hb Bart's for screening alpha(0)-thalassemia (--(SEA)) within the low MCV or MCH samples were 100%, 65.2%, 90.7%, 100% and 96.2%, 47.8%, 86.6%, 78.6%, respectively. All 4 alpha(0)-thalassemia (--(THAI)) traits were negative for zeta-globin chains but positive for Hb Bart's using the IC strip tests. These results led to a alpha(0)-thalassemia screening being proposed in which blood samples are first evaluated by MCV, MCH and Hb typing. Samples with high MCV and MCH values are excluded for the presence of the alpha(0)-thalassemia gene. Samples with low MCV or MCH values are assayed using the developed IC strip tests, where only samples testing positive are further assayed for alpha(0)-thalassemia by PCR. Patients with Hb H, EA Bart's or EF Bart's diseases do not need to use this IC strip assay. Thus, in this study, a simple and cost effective alpha(0)-thalassemia point of care test was developed.