**10.1 Pitfalls in screening tests for β-thalassemia and HbE carriers**


### **10.2 Pitfalls in confirmatory tests for β-thalassemia and HbE**

Normal hemoglobin type depends on age of the patients. Thus, reading and interpreting the hemoglobin typing results by all methodologies, age of the patients must be taken into account. In addition, transfused blood interferes the real

hemoglobin typing results of the patients. If the patients of β-thalassemia disease (βO/βO) have just received blood transfusion, their hemoglobin types will be A2AF, instead of A2F which is the real hemoglobin type of the βO/βO. If patients of HbE/ βO-thalassemia (β<sup>E</sup> /βO) have recent blood transfusion, their hemoglobin types will be EFA, instead of EF which is the real hemoglobin type of βO/β<sup>E</sup> . Therefore, recent blood transfusion should always be taken into account when reading and interpreting the hemoglobin typing results.

Co-existence of α-thalassemia 1 in β-thalassemia carrier and in HbE carrier can be found some regions. This is called double α-thalassemia 1/β-thalassemia carriers and double α-thalassemia 1 and HbE carriers. Results of one-tube osmotic fragility test are always positive in double α-thalassemia 1/β-thalassemia carriers, being the same as that of the single β-thalassemia carrier. However, MCV/MCH in double α-thalassemia 1/β-thalassemia carriers are slightly higher than those in the single β-thalassemia carriers (70.7 ± 2.6 vs. 68.4 ± 2.7 for MCV, 21.0 ± 1.2 vs. 20.7 ± 0.9 for MCH) [83]. HbA2 level in double α-thalassemia 1/β-thalassemia carriers is lower than that in single β-thalassemia carrier (5.27 ± 0.77% vs. 5.65 ± 0.78%) [29]. In contrast, the results of one-tube osmotic fragility test of double α-thalassemia 1/ HbE carrier are usually positive, being different from those of single HbE which can be either positive or negative. The MCV/MCH in double α-thalassemia 1/ HbE carrier are lower than those of the single HbE carrier (68.7 ± 8.9 fL vs. 75.7 ± 7.5 fL for MCV, 22.5 ± 3.1 pg vs. 24.9 ± 2.8 pg for MCH). HbE level in double α-thalassemia 1/HbE carrier are lower than those of the single HbE carrier (22.8 ± 4.4% vs. 27.6 ± 3.3%) [84]. Therefore, if HbE carriers have low HbE levels as well as MCV/MCH, further identification of α-thalassemia 1 genotype must be done.
