A novel means of identifying hemoglobin Tacoma utilizing capillary electrophoresis with a hemoglobin A1c software platform

Abstract Hemoglobin Tacoma (Hb Tacoma) results from the substitution of serine for arginine at position 30 in the β-globin chain resulting in instability in vitro, and has been identified with gel electrophoresis, isoelectric focusing and high-performance liquid chromatography (HPLC), but the role of capillary electrophoresis (CE) has never been reported. Whole blood samples were received from 4 patients for HbA1c testing at McMaster University Medical Centre (MUMC) in Hamilton, Canada, and initially analyzed via CE with Sebia Capillarys 2 Flex Piercing instrument using the Hb A1c platform. Specimens were then run on the hemoglobin variant platform and HPLC with additional studies including Hemoglobin H (Hb H) body staining, instability testing and β-globin gene sequencing. Hemoglobin concentrations were within normal reference intervals and mean corpuscular volume (MCV) was normal in most cases. Capillary electropherograms produced on the Hb A1c platform demonstrated a small double peak at the 271–273 mark area running past Hb A2 in all samples. On the variant hemoglobin program, Hb A2 percentage was mildly elevated, and a variant hemoglobin (Hb X) peak at 127–128 marks was identified and quantified at 35–37%, yielding a ratio of Hb A: Hb X of 1.7 to 1. Genetic confirmation was performed in 2 of the 4 cases. This series supports that Hb Tacoma heterozygosity is associated with in vitro instability without significant phenotypic consequences. We report identification of Hb Tacoma using CE and propose that CE with Hb A1c and variant hemoglobin platforms is an effective screening tool for Hb Tacoma.