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Master Thesis

Diagnostic sérologique de Toxoplasma gondii : analyse des IgG faux positifs et implications

Abstract : Introduction: Primary infection by Toxoplasma gondii in pregnant women can result in serious outcomes for the fetus. A false-positive IgG result during pregnancy can lead to a misdiagnosis of past infection and to stopping preventive measures.
Methods: We collected 189 sera with positive Architect® Toxo IgG assay (Abbott Laboratories) and negative IgG results with at least two other serological tests, in order to find an explanation for the suspected false-positive IgG results. We used the recomLine Toxoplasma IgG® immunoblot (Mikrogen Diagnostik) to search for specific antigenic reactivities of the sera, and the LDBio Toxo II IgG® immunoblot (LDBio Diagnostics) as a confirmatory test.
Results: The bands GRA8 and/or GRA7 were positive for 148 samples (78.3%). GRA8 was the most frequent band, appearing in 133 patterns (70.4%), whereas GRA7 was present for 49 samples (25.9%). Of the 81 samples tested with LDBio®, 23 (28.4%) turned out to be positive. Of the 58 negative LDBio® tests (71.6%) (real false-positive Architect® IgG), 23 samples (39.6%) did not show either a GRA8 or p30 band by recomLine®. Their false positivity with Architect® remains unexplained since Abbott uses these two recombinant antigens for their assay.
Conclusion: The Architect® IgG false positivity for T. gondii seems to be due to reactivity against GRA8 for the majority of the sera and GRA7 to a lesser extent. The hypothesis of past contact with parasites genetically close to T. gondii such as Hammondia hammondi or Neospora caninum seems promising and should be assessed further.
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Master Thesis
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Contributor : Bibliothèque Universitaire de Médecine Nice <>
Submitted on : Friday, October 16, 2020 - 3:53:51 PM
Last modification on : Thursday, April 22, 2021 - 3:12:30 AM


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  • HAL Id : dumas-02969431, version 1


Loïc Simon. Diagnostic sérologique de Toxoplasma gondii : analyse des IgG faux positifs et implications. Médecine humaine et pathologie. 2020. ⟨dumas-02969431⟩



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