In 44 heterozygous a1-thalassemia (2a/aa), posi- tive reactivity was observed in 6 samples (14%) with different intensity. Among the positives, 2 samples were from patients who have also b-thalassemia/Hb E diseases (Table I). Moreover, of 6 nondeletion a-thalas- semia heterozygotes, 3 heterozygous Hb Constant
Spring (CS) showed positive results, and 2 nondeletion a-thalassemias with mutation on the a2-globin gene (codon 94, A / G) showed the weakly positive results, whereas 1 sample with mutation on the a1-globin gene (codon 95, G / A) showed a negative reaction.
Among the 180 samples with normal a-globin geno- typing, the IC strip test revealed 97.8% negative reac- tivity. Four positive results, 2 each of normal and heterozygous for Hb E, were identified as the falsely positive. Given the high sensitivity (97.4%) and speci- ficity (93%) of the IC strip test for a0-thalassemia car- riers and its ease of use, a rapid screening method is considered as a valuable tool. A diagram showing how to interpret the results from the IC strip test is shown in Fig 1.