Hemoglobin (Hb) A2′ is a hematologically silent variant of HbA2 that is detected easily by high-performance liquid chromatography (HPLC), where it elutes in the S window. Our purposes were to define diagnostic criteria for the HbA2′ trait using the Variant II (Bio-Rad, Hercules, CA) and to determine the prevalence of HbA 2′ in a metropolitan patient population. All Hb screens (N = 5,862) performed during a 26-month period were reviewed for new hemoglobinopathies. We identified 57 cases of HbA2′ trait, making it the fourth most prevalent Hb variant detected in this population after HbS, HbC, and β-thalassemia minor. For HbA2′ trait cases, the mean HbA2 level was 1.7% (SD, 0.17%), and the mean HbA 2′ level was 1.3% (SD, 0.18%). Six possible HbA 2′/β-thalassemia double heterozygotes were identified, for whom the sum of the HbA2 and HbA2′ exceeded 4% of total Hb. Hb variants that might interfere with detection of HbA 2′ include HbS, glycosylated HbC, and HbG2. Diagnostic criteria proposed for the HbA2′ trait by HPLC are HbA2 of 2% or less, S window peak of 1% to 2%, no previous diagnosis of HbS, and absence of HbG and HbC.
- Hemoglobin electrophoresis
- High-performance liquid chromatography
- Isoelectric focusing
ASJC Scopus subject areas
- Pathology and Forensic Medicine