Serological diagnosis of<i>Toxoplasma gondii</i>: analysis of false-positive IgG results and implications

Simon, Loïc; Fillaux, Judith; Guigon, Aurélie; Lavergne, Rose‐Anne; Villard, Odile; Villena, Isabelle; Marty, Pierre; Pomarès, Christelle

doi:10.1051/parasite/2020006

Cited by 23 publications

(21 citation statements)

References 47 publications

(49 reference statements)

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“…For all EIAs except Bioplex and TGS/TA, the specificity exceeded 99%, which is not surprising, as these assays usually rely on immunocapture methods. However, Simon et al recently explored the question of false-positive results obtained with Architect Toxo IgG Ò , and found that 60% were due to cross-reaction with the parasite recombinant proteins GRA7 and GRA8; they suggest that exposure to closely related parasites, such as Hammondia hammondi or Neospora caninum, could explain these false-positive results [22]. Interfering immunoglobulins are mainly IgM, thus IgG EIAs infrequently suffer from non-specific reactions.…”

Section: Discussionmentioning

confidence: 99%

Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Robert‐Gangneux

Guegan

2021

Parasite

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Chronic infection with Toxoplasma gondii is attested by the detection of specific anti-Toxoplasma IgG. A wide panel of serologic methods is currently marketed, and the most suitable method should be chosen according to the laboratory resources and the screened population. This systematic review of evaluation studies aimed at establishing an overview of the performances, i.e. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of marketed anti-Toxoplasma IgG assays, and discussing their technical characteristics to guide further choice for routine diagnostic use. According to PRISMA guidelines, the search performed in PubMed and Web of Science databases recovered 826 studies, of which 17 were ultimately included. Twenty commercial anti-Toxoplasma IgG assays were evaluated, in comparison with an accepted reference method. Most of them were enzyme-immunoassays (EIAs, n = 12), followed by agglutination tests (n = 4), immunochromatographic tests (n = 3), and a Western-Blot assay (WB, n = 1). The mean sensitivity of IgG assays ranged from 89.7% to 100% for standard titers and from 13.4% to 99.2% for low IgG titers. A few studies pointed out the ability of some methods, especially WB to detect IgG early after primary infection. The specificity of IgG assays was generally high, ranging from 91.3% to 100%; and higher than 99% for most EIA assays. The PPV was not a discriminant indicator among methods, whereas significant disparities (87.5%–100%) were reported among NPVs, a key-parameter assessing the ability to definitively rule out a Toxoplasma infection in patients at-risk for opportunistic infections.

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Section: Discussionmentioning

confidence: 99%

Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Robert‐Gangneux

Guegan

2021

Parasite

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“…These should prove the absence of antigen recognition by sera from animals infected with tissue cysts [62,64] as well as absence of cross reactivity with closely related apicomplexan parasites. False positive results with a commercial test due to the likely presence of cross-reacting antibodies directed against GRA8 and GRA7 proteins from a previous exposure to other Sarcocystidae parasites have been reported [149]. In sheep, false positive results due to cross-reactions with N. caninum SAG1 and the chimeric SAG1-GRA8 as antigens were documented [150].…”

Section: Verification Of Protein Candidates To Identify Oocyst-driven T Gondii Infections: the Rationale Under A Proposed Workflow For Fumentioning

confidence: 99%

Identification of Oocyst-Driven Toxoplasma gondii Infections in Humans and Animals through Stage-Specific Serology—Current Status and Future Perspectives

et al. 2021

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The apicomplexan zoonotic parasite Toxoplasma gondii has three infective stages: sporozoites in sporulated oocysts, which are shed in unsporulated form into the environment by infected felids; tissue cysts containing bradyzoites, and fast replicating tachyzoites that are responsible for acute toxoplasmosis. The contribution of oocysts to infections in both humans and animals is understudied despite being highly relevant. Only a few diagnostic antigens have been described to be capable of discriminating which parasite stage has caused an infection. Here we provide an extensive overview of the antigens and serological assays used to detect oocyst-driven infections in humans and animals according to the literature. In addition, we critically discuss the possibility to exploit the increasing knowledge of the T. gondii genome and the various ‘omics datasets available, by applying predictive algorithms, for the identification of new oocyst-specific proteins for diagnostic purposes. Finally, we propose a workflow for how such antigens and assays based on them should be evaluated to ensure reproducible and robust results.

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“…Sometimes, conventional assays may require complementary testing in reference laboratories where sophisticated techniques and experienced personals are available [5,6] . Moreover, false positive, negative, and discrepant results between different commercial kits were recorded [7][8][9] .…”

Section: Serodiagnosismentioning

confidence: 99%

Performance of quantum dot nanobeads-based immunoassay in diagnosis of toxoplasmosis

El-Ghani

Abdelsalam

Ali

et al. 2021

Parasitologists United Journal

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Background: Diagnosis of toxoplasmosis relies mainly on determination of IgG and IgM using ELISA. However, inter-laboratory evaluation of performance of many commercial kits gave unsatisfactory agreements. Merging the innovative use of quantum dots nanobeads (QDNBs) immunoassay may yield higher sensitivity and specificity than the conventional used methods. Objective: The present study aims to evaluate the performance of QDNBs based immunoassay in serodiagnosis of human toxoplasmosis. Subjects and Methods: The study included 175 subjects divided into three categories; 122 patients with clinical manifestations suggestive of toxoplasmosis; 32 patients proved positive for other parasitic infections, and 21 healthy control subjects. In comparison to Sabin Feldman dye test (SFDT), as a gold standard test, serum samples were examined in an immunoassay utilizing QDNBs for detection of T. gondii specific IgG and IgM antibodies. Results: Compared to SFDT, combined QDNBs-IgG/IgM immunoassay exhibited sensitivity of 95.4%, specificity of 98.9%, positive predictive value (PPV) of 98.8%, and negative predictive value (NPV) of 95.6%, with relative agreement, validity, and accuracy of almost 97%. Conclusion:It was concluded that QDNBs-based immunoassay improves the performance of ELISA particularly sensitivity as well as shorten the assay time. QDNBs for diagnosis of toxoplasmosisAbd El-Ghani et al.,

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Serological diagnosis ofToxoplasma gondii: analysis of false-positive IgG results and implications

Cited by 23 publications

References 47 publications

Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Identification of Oocyst-Driven Toxoplasma gondii Infections in Humans and Animals through Stage-Specific Serology—Current Status and Future Perspectives

Performance of quantum dot nanobeads-based immunoassay in diagnosis of toxoplasmosis

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