Development and multicenter evaluation of the N latex CDT direct immunonephelometric assay for serum carbohydrate-deficient transferrin.
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 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 (r(2) = 0.862) and an HPLC candidate reference method (r(2) = 0.978).


CONCLUSIONS
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.
Delanghe
Joris R
JR
Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium. joris.delanghe@ugent.be
Helander
Anders
A
Wielders
Jos P M
JP
Pekelharing
J Maurits
JM
Roth
Heinz J
HJ
Schellenberg
François
F
Born
Catherine
C
Yagmur
Eray
E
Gentzer
Wolfgang
W
Althaus
Harald
H
D000293:Adolescent; D000437:Alcoholism / Q000175:diagnosis; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D001322:Autoanalysis; D015415:Biomarkers / Q000097:blood; D002648:Child; D018981:Congenital Disorders of Glycosylation / Q000175:diagnosis; D005189:False Positive Reactions; D005260:Female; D014644:Genetic Variation; D006031:Glycosylation; D006801:Humans; D007118:Immunoassay; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009391:Nephelometry and Turbidimetry; D012016:Reference Values; D012680:Sensitivity and Specificity; D014168:Transferrin / Q000031:analogs & derivatives* / Q000032:analysis / Q000235:genetics / Q000276:immunology
D000911:Antibodies, Monoclonal; D015415:Biomarkers; D014168:Transferrin; C056759:carbohydrate-deficient transferrin