Background: Congenital disorders of glycosylation (CDG) are usually diagnosed by isoelectric focusing (IEF) of serum transferrin (Tf). The aim of this study was to evaluate capillary zone electrophoresis (CZE) as a diagnostic alternative to IEF. Methods: We performed 792 CZE analyses of Tf, using the CEofix TM -CDT (carbohydrate-deficient transferrin) assay. Peak identification was based on relative migration times (RMTs) to reduce migration variability. Results: Tf profiles comprised three main groups (A-C).Groups A and B were characterized by one or two dominant tetrasialo-Tf peaks, whereas group C showed a widely variable Tf isoform composition. Group A was composed of four subgroups: a major group with a typical Tf profile (considered as reference group), two minor groups with decreased or moderately increased trisialo-Tf isoform, and a group showing the presence of unknown compounds with RMTs similar to mono-and disialo-Tf. However, these compounds were absent on IEF. Group C contained all profiles from patients with confirmed as well as putative CDG. From the reference group, 99% confidence intervals were calculated for the RMTs of the Tf isoforms, and percentiles representing the Tf isoform distributions were defined. Conclusions: All patients with abnormal IEF results and confirmed CDG were identified by CZE; thus, this method can be used as a diagnostic alternative to IEF in a manner suitable for automation. Because whole serum is analyzed, it should be kept in mind that CZE profiles can show substances other than Tf.

A modified agarose electrophoretic system for the separation of alkaline phosphatase (ALP, EC 3.1.3.1) isoenzymes is described. Bone, liver, high-molecular-mass, and intestinal ALP are separated with high reproducibility. The sensitivity of the agarose system is superior to cellulose acetate in detecting high-Mr ALP. Correlation is good between bone ALP fractions scanned before and after treatment with neuraminidase. Immunoglobulin-bound ALPs, the ALP-lipoprotein-X complex, and the additional ALP fraction observed in transient hyperphosphatasemia in children are detected by their peculiar electrophoretic mobility in the proposed system. Approximately 25% of the samples contained an additional fraction of intestinal-type ALP, as evidenced by neuraminidase treatment and use of polyclonal and monoclonal antibodies. Because the electrophoretic mobilities of this "intestinal variant" and of some immunoglobulin-bound ALP fractions are identical to those of bone and intestinal ALP, respectively, treatment of the samples with a polyclonal antibody that reacts with intestinal ALP is advised.

No abstract