A reassessment of o-toluidine for determination of xylose in serum and urine.

Therefore, it was somewhat surprising to find a normal, rather than very above-normal, concentration of glycosylated hemoglobin associated with a highly negatively charged fast hemoglobin variant. This patient was heterozygous for a fast hemoglobin variant; the high proportion of the variant hemoglobin (50%) and the lack of an abnormal HbA2 by cellulose acetate electrophoresis suggest a mutation at a fl-chain locus. In the case of a black patient, the most likely choice is HbN Baltimore (a2fl295 LYsGlu) (7,8). The normal glycosylated hemoglobin concentration here, as opposed to the decreased glycosylated hemoglobin concentrations associated with HbS and HbC (5), strongly suggests that the glycosylated fast variant hemoglobin and glycosylated HbA co-eluted. This is consistent with an increased isoelectric point secondary to glycosylation (6). This result, then,indicates thatglycosylated hemoglobin can be accurately assessed by cation-exchange chromatography in the presence of a fast (anodal at basic pH) hemoglobin variant.