Value of 2 IgG avidity commercial tests used alone or in association to date toxoplasmosis contamination

Lachaud, Laurence; Calas, Olivier; Picot, Marie Christine; Albaba, Sahar; Bourgeois, Nathalie; Pratlong, Francine

doi:10.1016/j.diagmicrobio.2009.02.014

Cited by 23 publications

(18 citation statements)

References 26 publications

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“…The cut-off values for low IgG avidity in our study were in accordance with the manufacturer’s recommendations and similar to values used in previous studies [ 19 , 22 , 23 ]. However, the cut-off values may have been too high, resulting in unnecessary amniocenteses in women with latent infection.…”

Section: Discussionsupporting

confidence: 69%

Management of suspected primary Toxoplasma gondii infection in pregnant women in Norway: twenty years of experience of amniocentesis in a low-prevalence population

Findal

Helbig

Haugen

et al. 2017

BMC Pregnancy Childbirth

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BackgroundPrimary infection with Toxoplasma gondii during pregnancy may pose a threat to the fetus. Women infected prior to conception are unlikely to transmit the parasite to the fetus. If maternal serology indicates a possible primary infection, amniocentesis for toxoplasma PCR analysis is performed and antiparasitic treatment given. However, discriminating between primary and latent infection is challenging and unnecessary amniocenteses may occur. Procedure-related fetal loss after amniocentesis is of concern. The aim of the present study was to determine whether amniocentesis is performed on the correct patients and whether the procedure is safe for this indication.MethodsRetrospective study analysing data from all singleton pregnancies (n = 346) at Oslo University Hospital undergoing amniocentesis due to suspected maternal primary toxoplasma infection during 1993–2013. Maternal, neonatal and infant data were obtained from clinical hospital records, laboratory records and pregnancy charts. All serum samples were analysed at the Norwegian Institute of Public Health or at the Toxoplasma Reference Laboratory at Oslo University Hospital. The amniocenteses were performed at Oslo University Hospital by experienced personnel. Time of maternal infection was evaluated retrospectively based on serology results.Results50% (173) of the women were infected before pregnancy, 23% (80) possibly in pregnancy and 27% (93) were certainly infected during pregnancy. Forty-nine (14%) women seroconverted, 42 (12%) had IgG antibody increase and 255 (74%) women had IgM positivity and low IgG avidity/high dye test titre. Fifteen offspring were infected with toxoplasma, one of them with negative PCR in the amniotic fluid. Median gestational age at amniocentesis was 16.7 gestational weeks (GWs) (Q1 = 15, Q3 = 22), with median sample volume 4 ml (Q1 = 3, Q3 = 7). Two miscarriages occurred 4 weeks after the procedure, both performed in GW 13. One of these had severe fetal toxoplasma infection.ConclusionsHalf of our study population were infected before pregnancy. In order to reduce the unnecessary amniocenteses we advise confirmatory serology 3 weeks after a suspect result and suggest that the serology is interpreted by dedicated multidisciplinary staff. Amniocentesis is safe and useful as a diagnostic procedure in diagnosing congenital toxoplasma infection when performed after 15 GW.

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Section: Discussionsupporting

confidence: 69%

Management of suspected primary Toxoplasma gondii infection in pregnant women in Norway: twenty years of experience of amniocentesis in a low-prevalence population

Findal

Helbig

Haugen

et al. 2017

BMC Pregnancy Childbirth

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“…The resulting titer of detectable IgG is used to calculate a ratio of titers obtained from treated and untreated samples; a highavidity index allows the exclusion of a recent infection with an accuracy of time which is technique dependent. This test was initially developed through "in-house" methods (200) but has been commercially available in Europe for about 10 years and has been evaluated in numerous studies (138,196,304). In the United States, the first FDA-approved test (Vidas Toxo IgG avidity assay; bioMérieux) was approved in 2011.…”

Section: Serologic Techniques and Interpretation (I) A Wide Range Ofmentioning

confidence: 99%

Epidemiology of and Diagnostic Strategies for Toxoplasmosis

2012

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SUMMARY The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.

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“…incorporated in decision algorithms used in national recommendations (4). Today, several commercial IgG avidity assays are available, although few cross-evaluations of their diagnostic performance have been published (11,(16)(17)(18). One of the primary goals of the French National Center for Toxoplasmosis was to evaluate the performance of the commercialized assays used in the French national screening program for congenital toxoplasmosis (19).…”

Section: Discussionmentioning

confidence: 99%

Comparison of Four Commercially Available Avidity Tests for Toxoplasma gondii-Specific IgG Antibodies

Villard

Breit

Cimon

et al. 2013

Clin Vaccine Immunol

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Toxoplasma infection in pregnant women may cause congenital toxoplasmosis. Diagnosis of infection is based on serological tests aimed at detecting IgM and IgG antibodies against Toxoplasma gondii. However, IgM antibodies are not an accurate marker for discriminating between acute and latent infection. Detection of residual or persistent IgM may occur months or even years after primary infection, while the IgG avidity test is a rapid means of identifying latent infections in pregnant women who exhibit both IgG and IgM anti-Toxoplasma antibodies on initial testing during pregnancy. In this study, we assessed and compared the performances of four commercially available Toxoplasma IgG avidity tests in immunocompetent and immunocompromised patients with acute and latent toxoplasmosis. The positive predictive value of high avidity to confirm latent toxoplasmosis was 100% for all the assays, indicating that high avidity is a hallmark of latent infection. However, the negative predictive value of high avidity ranged from 99.2% (bioMérieux) to 95.3% (Abbott), indicating that acute toxoplasmosis could not be reliably diagnosed based on low IgG avidity alone. Thus, the avidity test provides a rapid means for identifying latent Toxoplasma infection in immunocompetent pregnant women presenting both IgG and IgM anti-Toxoplasma antibodies on initial testing. In terms of cost-effectiveness, avidity testing is a powerful tool that optimizes screening and follow-up of pregnant women while minimizing the costs of screening by avoiding subsequent costly maternal and fetal investigation and unnecessary treatment. The cheapest assay, Vidas Toxo IgG Avidity, also had the best performance for the diagnosis of latent toxoplasmosis.

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Value of 2 IgG avidity commercial tests used alone or in association to date toxoplasmosis contamination

Cited by 23 publications

References 26 publications

Management of suspected primary Toxoplasma gondii infection in pregnant women in Norway: twenty years of experience of amniocentesis in a low-prevalence population

Management of suspected primary Toxoplasma gondii infection in pregnant women in Norway: twenty years of experience of amniocentesis in a low-prevalence population

Epidemiology of and Diagnostic Strategies for Toxoplasmosis

Comparison of Four Commercially Available Avidity Tests for Toxoplasma gondii-Specific IgG Antibodies

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