The effect of Sebia’s CZE IFCC-converted results on carbohydrate-deficient transferrin (CDT) interpretation in driver’s license assessments

OBJECTIVES: using HPLC. This study evaluates the impact of implementing Sebia's conversion equation on CDT measurements by capillary zone electrophoresis (CZE) for IFCC-alignment. METHODS: 8,309 serum samples from a driver's license regranting program and 226 samples from patients tested for congenital disorders of glycosylation (negative controls) were analyzed. Deming regression compared the original Sebia method with IFCC-aligned results following conversion. The upper limit of normal (ULN) was determined using control and population-based analyses. Age- and sex-dependent 0-sialo-Tf breakpoints were also evaluated. RESULTS: Sebia's conversion equation resulted in an upward shift in CDT within the 0-4 % range, increasing the proportion of positive samples by ∼80 % compared with the original Sebia method using a 2.3 % cut-off; applying the IFCC 2.0 % threshold still yielded a ∼50 % increase. The ULN was consistently 1.6 %, biological and analytical uncertainty correction supported the 2.0 % threshold. Although age- and sex-dependent 0-sialo-Tf breakpoints were statistically significant, exclusion of 0-sialo-Tf did not affect positivity, supporting 2-sialo-Tf as standalone marker. Longitudinal iQC monitoring confirmed reproducible quantification but revealed calibration-related positive shifts attributable to the conversion equation. CONCLUSIONS: Sebia's conversion equation increases the proportion of positive CDT results irrespective of the applied cut-off. However, our study demonstrates that Sebia's converted CDT, at a 2.0 % cut-off, is a robust marker for CDT measurement and achieves more harmonized CDT reporting.