Study of Axis-Shield new %CDT immunoassay for quantification of carbohydrate-deficient transferrin (CDT) in serum

Carbohydrate-deficient transferrin (CDT) in serum has emerged as a useful biochemical marker for identifying current alcohol misuse and monitoring abstinence. This study evaluated the performance of Axis-Shield new %CDT turbidimetric immunoassay (TIA; microtitre and Cobas Mira applications). Comparison was made with the previous Axis %CDT-TIA immunoassay (reference value <5.5%) and %CDT with the high-performance liquid chromatography (HPLC) technique (reference value <1.2%). The new %CDT assay measures primarily the asialo, monosialo and disialo transferrin isoforms, and the result is expressed as the amount relative to total transferrin. The analytical precision (coefficient of variation: CV) of the %CDT assay ranged between 3.1 and 8.5% for kit controls and serum samples. The %CDT values in serum from healthy social drinkers [i.e. Alcohol Use Disorders Identification Test (AUDIT) score 1-7 for men, and 1-5 for women] were 2.07 +/- 0.37% (mean +/- SD, range 1.4-3.3%, n = 100) and this was not significantly different from healthy non-drinkers (1.88 +/- 0.43%, 1.3-2.9%, n = 14), whereas abstinent alcohol patients showed slightly higher values (2.26 +/- 0.41, 1.7-3.4, n = 25). In chronic heavy drinkers (mean daily intake 225 +/- 137 g ethanol according to self-report), the %CDT values were markedly increased (6.33 +/- 4.01%, 1.2-18.0%, n = 107). There was no significant difference in %CDT values between male and female social drinkers. The reference value of the new %CDT assay to be used in clinical practice was tentatively set at <3.0%, which is slightly higher than that obtained by receiver operating characteristics (ROC) curve analysis (<2.8%) and that proposed by the manufacturer in the Instruction Manual (<2.6%). The %CDT assay showed good overall correlation with %CDT-TIA (r = 0.986, P < 0.0001) and %CDT-HPLC (r = 0.978, P < 0.0001). The specificity of the %CDT assay in healthy social drinkers was 98% (%CDT-TIA 100%, %CDT-HPLC 99%) and the sensitivity for any drinking during last week in the alcohol patients was 75% (%CDT-TIA 71%, %CDT-HPLC 80%). The new Axis-Shield %CDT assay can be recommended for routine use. However, whenever a positive immunoassay test result could lead to serious consequences for the individual, it is recommended to confirm the CDT result by the HPLC technique.