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Evaluation of qualitative agreement and quantitative correlation between the new ARCHITECT Toxo IgG assay and 4 commercially available Toxo IgG assays

Abstract number: P1885

Braun H.B., Sickinger E., Koch C., Birkenbach C., Stenzel I., Smith D., Schultess J., Hausmann M., Dhein J.

Objectives: Determination of Toxo IgG antibodies to Toxoplasma gondii is mainly important in pregnant women and immunocompromised patients to evaluate their serological status. Commercially available Toxo IgG assays are standardised against International standard preparations and report IU/ml concentrations. However, there were at least three different standard preparations available for standardisation of currently used Toxo IgG immunoassays, which might impact the quantitative correlation and slope between methods.

In this study we describe the qualitative agreement and quantitative correlation of the new ARCHITECT Toxo IgG assay, which is standardised against the WHO First International Standard (01/600) and utilizes recombinant antigens, and 4 other Toxo IgG assays standardised against earlier WHO standard preparations.

Methods: 100 pre-characterized Toxo IgG positive and 100 pre-characterized negative specimens were evaluated on the Vidas, Access, Enzygnost and AxSYM Toxo IgG assays in comparison to ARCHITECT Toxo IgG. Qualitative agreement and quantitative correlation was assessed.

Results: Qualitative agreement between the methods ranged from 98.9 to 100% without grey zone specimens and from 95.5 to 98.4% with grey zone specimens. Slope of linear regression between methods was very variable. The slopes and the correlation coefficient r versus Architect ranged from 0.8 to 3.0 and from 0.81 to 0.96, respectively.

Conclusion: Good qualitative agreement could be observed between all assays evaluated. Nevertheless, the differences in quantitative determination of concentrations were considerable. Quantitative differences can be attributed to differing standardisation, assay format and technology. This underlines the necessity to perform quantitative comparison of Toxo IgG levels within one method only.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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