Hb Riesa or β93 (F9) Cys→Ser, a new electrophoretically silent haemoglobin variant interfering with haemoglobin A1c measurement.

A new β variant was found in a German diabetic patient whose blood samples appeared to contain 45% Hb A1c using Bio-Rad Variant V-II A1c-analyzer but 7.6% on boronate affinity chromatography. Structural studies using, HPLC, mass spectrometry, and the genomic DNA analysis revealed a new substitution in which the cysteine residue at position β93 was replaced by serine. The variant was named Hb Riesa or β93 (F9) Cys→Ser and accounted for 54.3% of the total haemoglobin. This suggests that the protein-synthesis processes for the mutant could be slightly more promoted than those of the wild-type. Hb Riesa is clinically and electrophoretically silent.