Efficiency Assessment of EE Score for Differentiation of Homozygous HbE and β0-thalassemia/HbE

Abstract

β0-thalassemia/HbE and homozygous HbE are inherited disorders caused by an abnor- mal β-globin gene that impairs hemoglobin (Hb) synthesis in red blood cells. Diagnosis of both β0-thalassemia/HbE and homozygous HbE, in which patients having HbA2/E levels of >75% and

HbF levels of 5.1% to 19.9%, must be confirmed by DNA analysis. However, it is noted that the

use of the EE score can predict and classify β0-thalassemia/HbE. Therefore, this study aimed to evaluate the efficiency of EE score in identifying homozygous HbE and β0-thalassemia/HbE through a cross-sectional study. Blood samples of pregnant women and their husbands were collected for thalassemia screening in community hospitals in Health Area 9 and confirmatory

tests including levels and types of HbA2, HbE, HbF, and hemoglobinopathies were determined using capillary electrophoresis at Regional Health Promotion Center 9, Nakhon Ratchasima. A dataset of 142 subjects who were not interpretable for homozygous HbE and β0-thalassemia/

HbE, was used in this study. The values of HbA2 and HbF were used to calculate EE score. It was found that EE score ≤ 60 indicated homozygous HbE in 129 subjects, and EE score > 60 indicated β0-thalassemia/HbE in 13 subjects. The genotypes of thalassemia were examined using

real-time polymerase chain reaction (real-time PCR) as the standard method. The results showed that the EE score ≤ 60 group were 125 subjects with homozygous HbE and four subjects with homozygous HbE with α0-thalassemia trait, while the EE score > 60 group consisted of four subjects with homozygous HbE, one subject with homozygous HbE with α0-thalassemia trait, six subjects with β0-thalassemia/HbE, and two subjects with β0-thalassemia/HbE with α0- thalassemia trait. The EE score > 60 can be used to select samples for further DNA analysis with statistical quality of sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 96.3%, 61.5%, 100% and 96.5% respectively. The results indicated that

 the application of EE score showed high accuracy in predicting homozygous HbE and β0-thalassemia/HbE as well as exhibited a significant reduction of 90.8% in the number of samples for DNA analysis. Therefore, the EE score could be helpful in diagnosis for thalassemia prevention and control program.