Although all cases with a0-thalassemia gene gave positive results, the developed IC strip test also showed
positive reaction with homozygous a1-thalassemia and heterozygous Hb CS. The results are similar to those reported by Prayalaw et al.20 It is possible that there are certain amounts of Hb Bart’s in RBCs of these dis- orders because there are 2 a-globin gene deletions in homozygous a1-thalassemia and the Hb-CS mutation occurs on the more active a2-globin gene. In this
case DNA analysis is required to confirm the presence of a0-thalassemia, as homozygous a1-thalassemia will not lead to Hb Bart’s hydrops fetalis on interaction with a0-thalassemia gene. In the previous study, the so- called false positive test result was reported with a high percentage (83%) in a1-thalassemia heterozy- gote.20 However, in this study, only 13.6% of blood samples from a1-thalassemia heterozygote showed the positive IC strip test result. The weakly positive result also appeared in some b-thalassemia samples, especially in b-thalassemia/Hb E, but the interpretation for b-thalassemia disease is usually based on the clin- ical phenotype and Hb analysis. The positive result in these samples might suggest the presence of minute amount of Hb Bart’s (g4) because of the lack of a- and b-globin chains, indicating a high sensitivity of the test. Thus, the developed IC strip test in combina- tion with PCR among the positive cases can be used for detecting and ruling out of a0-thalassemia carriers (Fig 1). These results suggest that in combination with RBC indices, the IC strip test could rule out mass populations for further a0-thalassemia detection by PCR-based analysis. The established IC strip test has an advantage because it does not require sophisti- cated equipments, is easy to perform, and the result can be visually interpreted without expert. It is also less-time consuming and can be done with a large num- ber of samples. We, therefore, suggest that the IC strip test can be applied in screening program for thalas- semia, which will reduce the need of expensive PCR methods in the inappropriate cases for diagnosis of a0-thalassemia carriers.