Abnormal isoelectric focusing of serum transferrin Human serum transferrin has two N-glycosylation sites, which are normally both fully occupied by disialylated biantennary glycans to generate tetrasialotransferrin. HP:0003160 Abnormal isoelectric focusing of transferrin Glycosylated transferrin concentrations can be measured in serum as a marker of N-linked glycosylation fidelity. In the traditional nomenclature for congenital disorders of glycosylation, absence of entire glycans was designated type I, and loss of one or more monosaccharides as type II. These terms are retained for historical reasons but for new annotations the precise glycosylation defect should be recorded. Abnormal transferrin isoelectric focusing UMLS:C2749688 Abnormal protein N-linked glycosylation