Evaluation of the new Vidia^® toxoplasmosis IgG and IgM assays in women of childbearing age

Abstract number: 1733_53

Zufferey J., Di Mito C., Auckenthaler R.

Objectives: The aim of the present study was to evaluate the performance of the new VIDIA^® Toxoplasmosis IgG and IgM assays (bioMérieux, France), using the VIDIA^® system easy to use with a high level of traceability, with clinical specimens prospectively collected in women of childbearing age.

Methods: A total of 1000 fresh serum samples consecutively obtained from 1000 women aged 18–44 years (median 30) during a period of 4 weeks were tested with ADVIA^® Centaur^TM Toxoplasma IgG and IgM assays according to routine conditions. Serum aliquots stored at + 4°C were blindly rechecked within 24 hours with the VIDIA system for the same parameters. Discrepancies of results between both methods were resolved considering avidity test, direct agglutination (Toxo-Screen DA, bioMérieux), ISAGA (bioMérieux) and when available, the analysis of previous drawn serum samples.

Results: Among the 1000 women screened with VIDIA, 89.4% had non detectable IgG and IgM (T. gondii seronegative) and 8.2% had a pattern of past acquired infection (positive IgG and no detectable IgM). Positive IgM were detected in 1.1% of them with VIDIA system versus 2% with ADVIA Centaur. Equivocal rate was 0.9% for VIDIA TOXO IgG and 0.5% for VIDIA TOXO IgM (versus 0.9% and 1.1%, respectively for the compared method).

For VIDIA TOXO IgG the relative sensitivity and specificity were 96.7% and 99.7%, respectively. After the resolution of discrepancies, the sensitivity as well as the specificity was 100%.

For VIDIA TOXO IgM the initial relative sensitivity and specificity were 64.7% and 100%, respectively. In fact, 4 of the 6 negative samples with VIDIA and positive with the compared method were found with high avidity index and the remaining two samples were negative with the reference test (ISAGA-IgM). Taking this into account, the absolute sensitivity was found 100%.

Conclusion: The two evaluated assays VIDIA TOXO IgG and TOXO IgM have shown an excellent sensitivity and specificity and are well adapted to the routine screening of toxoplasmosis in pregnant women.