Insufficient Standardization of a Direct Carbohydrate-Deficient Transferrin Immunoassay

Abstract

Measurement of carbohydrate-deficient transferrin (CDT) can reveal alcohol-related changes in the serum transferrin glycosylation pattern. CDT is a more alcohol-specific indicator than liver-function tests and is used for identification and follow-up of chronic high alcohol consumption(1). Therefore stable calibration of the assays is very important. Comparison of CDT results between methods has often been hindered by method-dependent discrepancies in the definition of the measurand (the transferrin glycoforms covered) and the way results are expressed. With some methods there has been an increased risk for false-positive results(2). The lack of CDT standardization prompted initiation of a working group under the International Federation of Clinical Chemistry and Laboratory Medicine, whose aim was to define the measurand, select and validate a reference method, and work out procedures for the production of reference materials. The first recommendation was that the fraction of disialotransferrin to total transferrin (%disialotransferrin) should be the primary target for CDT testing, with HPLC as the candidate reference method(3). The performance of individual laboratories and agreement of different methods can be determined through external quality assessment (EQA). A Swedish EQA scheme for CDT has been run by EQUALIS (External …