Evaluation of capillary electrophoresis assay for CDT on SEBIA's Capillarys System: intra and inter laboratory precision, reference interval and cut-off.
BACKGROUND
Carbohydrate-deficient transferrin (CDT) measurement on the multicapillary system Capillarys™ is characterized by high throughput and an on-line sample pre-treatment. This study evaluates the linearity and the precision of this technique, the correlation with the candidate reference method and the effect of genetic transferrin variants. Upper reference limit and cut-off values were calculated.


METHODS
The precision study was carried out following CLSI EP5-A protocol. The between laboratory variation was calculated from an eight-site study. The upper reference limit (URL) was conventionally calculated from a reference population of 225 samples and verified by a Bhattacharya analysis in a large (n=19,129) population. A population of 314 heavy consumers was used for calculation of the cut-off limit. Additionally the measurement uncertainty was calculated according to EDMA (European Diagnostic Manufacturers Association) and IRMM.


RESULTS
The imprecision found was less than 5%, linearity was excellent for CDT values ranging from 2% to 20%. The between site variation around the cut-off value (CDT ranging from 1.68% to 1.79%) was clinically not significant. The upper reference limit (95th percentile) was calculated at 1.3% by the conventional IFCC method and confirmed by Bhattacharya calculations. The optimum cut-off for this CZE method was 1.6%, taken into account the measurement uncertainty. The regression equation with the candidate reference method was Disialotransferrin(Capillarys2)=Disialotransferrin(HPLC)∗0.968-0.248. Genetic variants and abnormal profiles were well recognized.


CONCLUSIONS
These results demonstrate that the Capillarys CDT method is robust and reliable in routine use with a high degree of homogeneity from one system to another and is highly correlated with the candidate HPLC reference method.
Schellenberg
François
F
Laboratory of Biochemistry, hôpital Trousseau, CHRU de Tours, 37044 Tours, France. f.schellenberg@chu-tours.fr
Wielders
Jos P M
JP
D000293:Adolescent; D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D019411:Clinical Laboratory Techniques; D019075:Electrophoresis, Capillary / Q000379:methods* / Q000592:standards*; D005260:Female; D014644:Genetic Variation; D006801:Humans; D038622:Internationality; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014168:Transferrin / Q000031:analogs & derivatives* / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification; D035501:Uncertainty; D055815:Young Adult
D014168:Transferrin; C056759:carbohydrate-deficient transferrin