[Characteristics of Silent Alpha Thalassemia Gene in Child-Bearing Adults in Guangdong].

Objective: To investigate characteristics of silent alpha thalassemia genes in child-bearing adults in Guangdong, in order to provide data for the prevention and control of hemoglobin H disease.

Methods: A total of 8 752 cases were collected from January 2016 to December 2020. Gap-PCR was used to detect the deletional of α-thalassemia mutations (-α, -α), while PCR reverse dot blot hybridization assay (RDB) was used to detect the non-deletional α-thalassemia mutations (Hb CS, Hb QS and Hb Westmead).

Results: Among 8 752 subjects, 717 cases of silent α-thalassemia were detected, the detection rate was 8.19%, including 555 cases of deletional α-thalassemia (77.41%) and 162 cases of non-deletional α-thalassemia 22.59%. The mean corpuscular volume (MCV) of deletional silent α-thalassemia was (82.09±4.10) fl, and mean corpuscular hemoglobin (MCH) was (27.03±1.37) pg, which both were over the diagnostic cut-off value for thalassemia. The MCV of non-deletional silent α-thalassemia was (81.07±4.93) fl, and MCH was (26.77±2.20) pg. According to the diagnostic criteria, if using MCV<82 fl or (and) MCH<27 pg as a positive criteria for screening thalassemia in the childbearing age, the screening sensitivity was 53.14% and different in different genotype, among which αα/αα was 100%, -α/αα, -α/αα, αα/αα and αα/αα was 62.15%, 63.41%, 44.83% and 39.62%, respectively. Namely, nearly half the carriers of such mutations might have escaped detection as a result of their screening strategy.

Conclusion: When a couple is preparing for pregnancy, if one of them has been determined to be mild α-thalassemia or hemoglobin H disease, other half is necessary to carry out silent α thalassemia detection to prevent the birth of children with hemoglobin H disease even if MCV>82 fl and MCH>27 pg.