Background: Carbohydrate-deficient transferrin (CDT) is used for the laboratory diagnosis of chronic alcohol abuse. Non-optimal preanalysis can cause an increase in CDT and false positive results. The aim of our study was to determine whether CDT results change over time between collection of the blood sample and centrifugation, and whether shipment of whole blood samples is a potential source of false positive CDT reports.
Material/methods: 152 blood samples were drawn from 38 persons (4 tubes per person, one venipuncture) and randomly assigned to 4 groups with different time intervals between blood sample collection and centrifugation (1h, 24h, 48h, 144h). CDT analysis was done using the ChronAlcoI.D. assay. The statistical analysis was based on box-plots, ANOVA and Kruskal-Wallis ANOVA.
Results: The means and medians of CDT increased with the time of whole blood storage. ANOVA analysis of between-group differences was significant for mean CDT concentrations between 1 and 144 hours of whole blood storage. There was no correlation between CDT and free hemoglobin as a measure of hemolysis. An interference of hemolysis with CDT measurement can be excluded as the main cause of increased CDT results with whole blood storage time. Whether an in vitro degradation of the transferrin N-glycan chains causes the CDT increase should be evaluated by isoelectric focusing of the transferrin isoforms in a further study.
Conclusions: Storage or shipment of whole blood samples can shift initially normal CDT values to borderline and borderline to pathological CDT results.