Received on December 11, 2006
Accepted on March 8, 2007

Automation and Analytical Techniques

Development and Multicenter Evaluation of the N Latex CDT Direct Immunonephelometric Assay for Serum Carbohydrate-Deficient Transferrin

¹ Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium
² Alcohol Laboratory, Karolinska Institute and Karolinska University Hospital, Stockholm, Sweden
³ Department of Clinical Chemistry, Meander Medical Center, Amersfoort, The Netherlands
⁴ Reinier de Graaf Groep, Diagnostic Center SSDZ, Delft, The Netherlands
⁵ Limbach Laboratories, Heidelberg, Germany
⁶ Laboratory of Clinical Chemistry, Hopital Trousseau, Centre Hospitalier Régional Universitaire, Tours, Tours, France
⁷ Institut Regional pour la Sante, La Riche, France
⁸ Central Laboratory, University Hospital, Rheinisch Westfälische Technische Hochschule, Aachen, Germany
⁹ Research Laboratories, Dade Behring Marburg GmbH, Marburg, Germany

^* To whom correspondence should be addressed. E-mail: joris.delanghe{at}ugent.be.

Background: Carbohydrate-deficient transferrin (CDT) is a promising biomarker of alcohol abuse. We describe the development and multicenter evaluation of N Latex CDT (Dade Behring), an automated, particle-enhanced, homogeneous immunonephelometric assay for directly determining CDT.

Methods: N Latex CDT uses a monoclonal antibody that recognizes the structure of transferrin glycoforms lacking 1 or 2 complete N-glycans [i.e., disialo-, monosialo-, and asialotransferrins (CDT glycoforms)] in combination with a simultaneous assay for total transferrin. The Dade Behring BN II^TM and BN ProSpec^® systems automatically calculate the CDT value as a percentage of total transferrin (%CDT). No preanalytical sample treatment is used.

Results: Total imprecision values for serum pools containing 1.8%-8.7% CDT were 3.4%-10.4% (mean, 6.8%). The mean (SD) %CDT for 561 serum samples from healthy control individuals was 1.76% (0.27%; range, 1.01%-2.85%). No marked sex or age differences were noted. The 97.5th percentile was at 2.35%. Transferrin genetic variants did not interfere with measurements. High transferrin concentrations did not falsely increase %CDT values, but increased %CDT values were noted for some samples with transferrin concentrations <1.1 g/L. N Latex CDT results correlated with those of a commercial CDT immunoassay involving column separation (r² = 0.862) and an HPLC candidate reference method (r² = 0.978).

Conclusion: N Latex CDT is the first direct immunoassay for quantifying %CDT in serum. The specificity of N Latex CDT for identifying alcohol abuse may be higher than for immunoassays that use column separation, because transferrin genetic variants do not interfere with measurements.