2021 Volume 64 Issue 7 Pages 395-401
A 36-year-old male Thai patient visited our hospital because of a high HbA1c level and microcytic hypochromic anemia (RBC 5.56×1012/L, Hb 9.7 g/dL, MCV 65.3 fL). His plasma glucose and HbA1c values as determined by TOSOH HLC-723-G11 were 87 mg/dL and 10.9 %, respectively. The plasma glucose on the 75-g OGTT was 89 mg/dL (before) and 104 mg/dL (after 2 h). The glycoalbumin and 1,5-AG levels were normal at 13.2 % and 25.8 μg/dL, respectively. Thus, the HbA1c value measured in our laboratory seemed to be spuriously elevated. Supravital staining of RBCs with Brilliant crysyl blue demonstrated frequent Hemoglobin H (HbH; β4) inclusion bodies. A gene analysis revealed [--/αTα]-type HbH disease, where non-deletion-type α thalassemia (αT) was Hb Constant Spring [HBA2: c.427T>C, or Codon142 TAA (Stop) →CAA (Gln) ]. A pair of α globin genes deleted in cis [--/] was of Southeast Asian-type α0 thalassemia. The presence of denatured HbH may have given rise to spuriously elevated HbA1c values because of its co-elution with normal HbA1c on high-performance liquid chromatography. αT including Hb Constant Spring is common among Southeast Asians, a population that is relatively large in Japan. Thus, Japanese physicians need to be careful when interpreting the significance of HbA1c findings when they encounter such patients in their clinic.
