The Hb E (HBB: c.79G>A), Mean Corpuscular Volume, Mean Corpuscular Hemoglobin Cutoff Points in Double Heterozygous Hb E/- -SEA α-Thalassemia-1 Carriers are Dependent on Hemoglobin Levels.

Identifying double heterozygosities in Hb E (HBB: c.79 G>A)/- -SEA (Southeast Asian) (α-thalassemia-1) (α-thal-1) in patients first diagnosed as carrying Hb E is important in thalassemia control. Low Hb E, mean corpuscular volume (MCV) and mean corpuscular hemoglobin (Hb) (MCH) levels have been observed in this double heterozygosity. However, the cutoff points of these parameters have never been systematically established. Here, we analyzed Hb E and red blood cell (RBC) parameters in 372 Hb E patients grouped by Hb levels, by the status of - -SEA and -α3.7 (α-thal-2; rightward) deletions, to establish the cutoff points. Then, the established cutoff points were evaluated in 184 Hb E patients. It was found that the cutoff points of Hb E, MCV, MCH were significantly dependent on the Hb levels. In the group having Hb levels <10.0 g/dL, the cutoff points of Hb E, MCV and MCH were 21.2%, 64.9 fL and 21.0 pg, respectively, and were 25.6%, 72.8 fL and 23.9 pg, respectively, in the group having Hb levels 10.0-11.9 g/dL. Finally, in the group having Hb levels ≥12.0 g/dL, the cutoff points of Hb E, MCV and MCH were 27.1%, 76.7 fL and 25.3 pg, respectively. Thus, to screen for the double heterozygous Hb E/- -SEA anomaly in patients initially diagnosed as carrying Hb E, the Hb levels must be taken into account in choosing the suitable cutoff points of these three parameters.