Diagnostic Value of IgG Avidity in<i>Toxoplasma</i>Infection: Comparison of 3 Commercial Kits

Barberi, A; Gistri, A.; Cappelletti, Francesca; Giordano, I.

doi:10.1086/323399

Cited by 11 publications

(15 citation statements)

References 9 publications

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“…From the immunological point of view, however, IgG affinity maturation represents a very complex mechanism(s) which may be further modified by hormones developed during pregnancy (Szekeres-Bartho 1993;Malan Borel et al 1991) as well as by treatment with antibiotics (Barberi et al 2001;Pelloux et al 1998). Therefore, the validity of the test cannot be significantly improved only by changing the concentration of urea as done by Beghetto et al (2003).…”

Section: Discussionmentioning

confidence: 99%

Usefulness of Toxoplasma gondii recombinant antigens (GRA1, GRA7 and SAG1) in an immunoglobulin G avidity test for the serodiagnosis of toxoplasmosis

et al. 2006

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The precise diagnosis of an acute and recent Toxoplasma infection in pregnant women and the newborn child is important before treatment. This study describes a new Toxoplasma gondii IgG avidity test based on a combination of recombinant GRA1, GRA7 and SAG1 antigens and shows that this test is useful for diagnostic purposes and may replace the lysed, whole-cell antigens. Although more sera need to be tested, the results obtained here suggest that the IgG avidity test performed with rec-antigens correlated more with the stage of a T. gondii infection than the IgG avidity results obtained with the lysed, whole-cell antigen test, the VIDAS Toxo IgG avidity (bioMérieux).

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Section: Discussionmentioning

confidence: 99%

Usefulness of Toxoplasma gondii recombinant antigens (GRA1, GRA7 and SAG1) in an immunoglobulin G avidity test for the serodiagnosis of toxoplasmosis

et al. 2006

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“…It does not allow us to make a decision regarding interruption of pregnancy, but on the other hand, it permits us to reassure a large number of patients at the beginning of pregnancy when the AI is Ͼ0.3. This test has been developed as a routine test in many European countries (3,11,19) and in South America, where it is commercialized. In addition, it has FIG.…”

Section: Discussionmentioning

confidence: 99%

“…It permits dating (an avidity index [AI] of Ͼ0.3 means that infection occurred more than 4 months ago) and excludes infection that has occurred after the onset of pregnancy (1,8,19). However, some recent studies have shown the limitations and difficulty in interpreting the results of this test (3,18). Different parameters can modify the increase in the AI during the course of seroconversion.…”

mentioning

confidence: 99%

Reliability of Immunoglobulin G Antitoxoplasma Avidity Test and Effects of Treatment on Avidity Indexes of Infants and Pregnant Women

Flori

Tardy

Patural

et al. 2004

Clin Vaccine Immunol

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The immunoglobulin G antitoxoplasma avidity test (Vidas; BioMérieux) is an immunoenzymatic test useful for excluding acute infection after the onset of pregnancy. The avidity index (AI) is the ratio of the signal in a test sample washed with urea, which disrupts low-avidity complexes, to that washed without urea. An AI of >0.3 is taken to mean that infection had occurred more than 4 months ago. The increase of the AI with time and the influence of the different treatments given to pregnant women and their newborns were evaluated. A total of 59 pregnant women (271 sera) and their 60 neonates (199 sera) were tested from 1998 to 2002. There were five groups of women based on the type and duration of treatment given. Thirteen pregnant women (group 1) did not receive any treatment, 15 (group 2), 11 (group 3), and 17 (group 4) women received treatment with spiramycin (9 MIU/day) for 0.5 to 2, 2.5 to 5, and 5.5 to 8 months, respectively, and the last 3 women (group 5) received tritherapy (pyrimethamine-sulfonamide and spiramycin alternatively) for 1.5 to 2.5 months. All of the maternal sera collected in the first 6 months had an AI of <0.30, with a mean of 0.07 (range, 0.01 to 0.21). The increase was slow (0.02/month), and there was no significant difference when comparisons were made between the treatment groups. Neonates with proven maternofetal transmission had an increasing AI, unlike those without transmission. However, long-term therapy with pyrimethamine-sulfonamide, as opposed to treatment with spiramycin alone, was found to slow down the progression of the AI. An AI of >0.2 is sufficient to exclude acute infection in pregnant women. In neonates, it is not of major use to diagnose congenital infection; however, it could be a good indicator of compliance and efficacy of treatment of infected infants.Toxoplasmosis, caused by Toxoplasma gondii, is widespread in humans and warm-blooded animals. Although usually asymptomatic in immunocompetent humans, toxoplasmosis may cause severe disorders in immunocompromised individuals and in pregnant women because of the high risk of transplacental transmission and the occurrence of abortion or multiple congenital lesions in the fetus (7, 9). In France, specific immunoglobulin G (IgG) and IgM antibody evaluation is mandatory in the first trimester of pregnancy. The presence of toxoplasma-specific IgM at the time of the first blood test is a cause for concern. In certain cases it could either be nonspecific IgM (8,10,[16][17]26) or residual IgM from a previous infection (8,12,16,20). In the remaining cases, it could of course be due to an acute infection. To confirm the latter, the presence of an associated elevated IgG level allows a complementary test to be done: the avidity test.The avidity test (Vidas; BioMérieux, Marcy l'Etoile, France) is of major interest when it is done during the first trimester of pregnancy. It permits dating (an avidity index [AI] of Ͼ0.3 means that infection occurred more than 4 months ago) and excludes infection that has occurred after the onset of...

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“…Urea is the common chaotrope used (CAMARGO et al, 1991), an alternative to ammonium thiocyanate (FERREIRA & KATZIN, 1995). Several studies have reported that the avidity of antibody IgG is a good index of the time of the infection, defining if the acute infection has occurred in the past few months despite conflicting results between tests (BARBERI et al, 2001). Recombinant antigens were frequently tested in serology for toxoplasmosis (SUZUKI et al, 2001), usually with adequate but weak screening results compared to whole extracts in ELISA ( VAN GELDER et al, 1993 (BEGHETTO et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…The avidity determination was reliable for each isolated antigen regardless of the chaotrope agent, demonstrating that avidity determination is dependent on each antigen and its preparation for determination of recently acquired infections. This data could explain the conflicting results reported when comparing commercial tests available for avidity determination (BARBERI et al, 2001). Avidity is the summation of the specific antibody affinities after an infection.…”

mentioning

confidence: 99%

Serology using rROP2 antigen in the diagnostic of toxoplasmosis in pregnant women

Macre¹,

Pires²,

Meireles³

et al. 2009

Rev. Inst. Med. trop. S. Paulo

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SUMMARYToxoplasma gondii causes severe fetal disease during acute infection in pregnant women, thus demanding early diagnosis for effective treatment and fetus preservation. Fetal tests are inefficient and risky, and diagnosis is based on maternal IgM serology, which had weak screening ability due to increased sensitivity, with alternative IgG avidity tests. Here, we performed ELISA and avidity assays using a recombinant T. gondii antigen, rROP2, in samples from 160 pregnant women screened from a large public hospital who were referred due to positive IgM assays. IgG serology and avidity assays were compared using whole T. gondii extract or rROP2. ELISA IgG detection with rROP2 showed good agreement with assays performed with T. gondii extract, but rROP2 IgG avidity assays were unrelated to whole extract antigen IgG avidity, regardless of the chaotrope used. These data show that avidity maturation is specific to individual antigen prevalence and immune response during infection. ELISA rROP2 IgG assays may be an alternative serological test for the diagnosis of toxoplasmosis during pregnancy, although our data do not support their use in avidity assays.

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Diagnostic Value of IgG Avidity inToxoplasmaInfection: Comparison of 3 Commercial Kits

Cited by 11 publications

References 9 publications

Usefulness of Toxoplasma gondii recombinant antigens (GRA1, GRA7 and SAG1) in an immunoglobulin G avidity test for the serodiagnosis of toxoplasmosis

Usefulness of Toxoplasma gondii recombinant antigens (GRA1, GRA7 and SAG1) in an immunoglobulin G avidity test for the serodiagnosis of toxoplasmosis

Reliability of Immunoglobulin G Antitoxoplasma Avidity Test and Effects of Treatment on Avidity Indexes of Infants and Pregnant Women

Serology using rROP2 antigen in the diagnostic of toxoplasmosis in pregnant women

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