BACKGROUND: Carbohydrate-deficient transferrin (CDT) is used for the laboratorydiagnosis of chronic alcohol abuse. Non-optimal preanalysis can cause an increase in CDT and false positiveresults. The aim of our study was to determine whether CDT results change over time between collectionof the blood sample and centrifugation, and whether shipment of whole blood samples is a potential sourceof false positive CDT reports. MATERIAL/METHODS: 152 blood samples were drawn from 38 persons (4 tubesper person, one venipuncture) and randomly assigned to 4 groups with different time intervals betweenblood 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: Themeans and medians of CDT increased with the time of whole blood storage. ANOVA analysis of between-groupdifferences 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 ofhemolysis with CDT measurement can be excluded as the main cause of increased CDT results with wholeblood storage time. Whether an in vitro degradation of the transferrin N-glycan chains causes the CDTincrease 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 borderlineand borderline to pathological CDT results.

Keywords: Blood, Centrifugation, False Positive Reactions, Phlebotomy, Specimen Handling, Time Factors, Transferrin