Performance validation of a third-generation allergen-specific IgE assay in the clinical laboratory: interlaboratory and intermethod comparison.
BACKGROUND
Allergen-specific IgE (sIgE) measurements are used to help identify causative allergenic agents and to determine the degree of sensitization to facilitate treatment decisions. We examined the performance of a new third-generation chemiluminescent enzyme immunoassay for allergen-specific IgE (sIgE) on the continuous random access Immulite 2000 system.


METHODS
Detection limit and dilutional linearity were determined. Within-run and total precision were assessed according to the NCCLS EP5 guideline. Interlaboratory comparison of the new Immulite 2000 third-generation allergen-specific IgE assay was performed, as well as intermethod comparison against the Pharmacia FEIA, a second-generation assay.


RESULTS
The detection limit was <0.1 kU/l. Dilutional linearity held from 100 down to 0.2 kU/l. Regression analysis of the interlaboratory comparison results yielded: Immulite 2000(Laboratory 1)=1.07 Immulite 2000(Laboratory 2)+0.18 kU/l; r=0.98, n=3588 results. Intermethod comparison showed the following: Immulite 2000=0.83 (Pharmacia FEIA)+0.42 kU/l; r=0.79, n=512 results. Bland-Altman analysis of the interlaboratory and intermethod comparisons indicated no systematic bias.


CONCLUSIONS
We confirmed the reported performance characteristics of the third-generation sIgE assay and found reasonably good interlaboratory and intermethod agreement. The extended range capability of the third-generation assay provides a new tool for investigating cutoffs and trends in childhood allergy disease progression at concentrations <0.35 kU/l.
Invitrogen, 1610 Faraday Avenue, Carlsbad, CA 92008, USA. thomas.li@invitrogen.com
Thomas M
TM
Li
Paul
P
Fu
Vlasta
V
Zic
D000485:Allergens / Q000276:immunology*; D000918:Antibody Specificity; D003876:Dermatitis, Atopic / Q000097:blood / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007073:Immunoglobulin E / Q000097:blood* / Q000276:immunology*; D015203:Reproducibility of Results
D000485:Allergens; D007073:Immunoglobulin E