Diagnostic performance of hemoglobin A2 and hemoglobin E for thalassemia screening in a Southern Chinese population

Background: Hemoglobin A2 (HbA2) is an established laboratory biomarker for thalassemia screening; however, its diagnostic performance may be influenced by demographic characteristics and hemoglobin variants. Hemoglobin E (HbE), a common structural hemoglobin variant in Southern China, may affect the interpretation of HbA2 results and reduce screening accuracy when conventional cut-off values are applied. This study aimed to evaluate the clinical utility of HbA2 and HbE in thalassemia screening and to establish optimized HbA2 cut-off values for improving diagnostic performance in a Southern Chinese population. Methods: A total of 1,352 individuals were retrospectively enrolled, including 355 a-thalassemia carriers, 174 b-thalassemia carriers, and 823 genetically normal controls. Complete blood count parameters, capillary electrophoresis (CE) results, and thalassemia genotypes determined by polymerase chain reaction-reverse dot blot (PCR-RDB) analysis were collected. Receiver operating characteristic (ROC) curve analysis was performed to determine optimal HbA2 cut-off values for thalassemia screening in men, non-pregnant women, and pregnant women. Results: Thirteen a-thalassemia genotypes and ten b-thalassemia genotypes were identified. For a-thalassemia screening, the optimal HbA2 cut-off values were <2.5%, <2.4%, and <2.6% in men, non-pregnant women, and pregnant women, respectively. HbE carriers exhibited significantly lower HbA2 levels than other b-thalassemia carriers, indicating that HbE should be interpreted as an independent laboratory marker during screening. After exclusion of bE (GAG>AAG)/bN individuals, the optimal HbA2 cut-off values for b-thalassemia screening were >4.0%, >4.1%, and >4.7% in men, non-pregnant women, and pregnant women, respectively. The optimized screening model demonstrated improved positive and negative predictive values compared with conventional HbA2-based criteria. Conclusion: HbA2 demonstrates good diagnostic accuracy for thalassemia screening when population-specific thresholds are applied. Combined assessment of HbA2 and CE-detected HbE improves screening performance and enhances the identification of both aand b-thalassemia carriers. These findings support the clinical application of individualized laboratory screening strategies and provide evidence for optimizing thalassemia screening protocols in high-prevalence populations.