Reference intervals for HbA2 and HbF and cut-off value of HbA2 for β-thalassemia carrier screening in a Guizhou population of reproductive age

Abstract

Objective: The aims of this study were to establish the reference intervals for HbA2 and HbF in a Guizhou population of reproductive age, and to determine the cut-off value of HbA₂ for β-thalassemia carrier screening.

Methods: Hemoglobin analysis was performed on 832 individuals without hypochromic microcytic anemia to calculate the reference intervals for HbA₂ and HbF. Three hundred and ninety one β-thalassemia carriers and non β-thalassemia individuals were analyzed for their HbA₂ levels followed by detecting β-globin gene mutations, then cut-off value of HbA₂ for β-thalassemia carrier screening was determined using ROC curve analysis.

Results: The reference interval for HbA₂ in overall normal individuals was 2.3%-3.1%, and reference intervals for HbF in normal males and females (including normal females and pregnant women) were 0-0.5% and 0-1.0% respectively. The cut-off values of HbA₂ for β-thalassemia carrier screening in males, non-pregnant women, pregnant women and the overall set were 4.40%, 3.75%, 3.70% and 3.95% respectively.

Conclusion: Gender and pregnancy status had no obvious influence on reference interval for HbA₂. The HbF level was higher in females than in males, but pregnancy status had no obvious influence on HbF level. Cut-off value of HbA₂ for β-thalassemia carrier screening was obviously affected by gender but not by pregnancy status.

Keywords: Cut-off value; HbA(2); HbF; Reference interval; β-thalassemia.