Evaluation of the new Elecsys Toxo IgG avidity assay for toxoplasmosis and new insights into the interpretation of avidity results

Evaluation of different cut-off points for IgG avidity and IgM in the diagnosis of acute toxoplasmosis in pregnant women participating in a congenital toxoplasmosis screening program

The main social impact of toxoplasmosis stems from its ability to be vertically transmitted. Postnatally acquired infection is generally asymptomatic in approximately 70-90% of cases, making diagnosis often dependent on laboratory tests using serological methods to search for anti-T. gondii antibodies. This study aimed to investigate the ability of the VIDAS TOXO IgG avidity and VIDAS TOXO IgM assays to confirm recent toxoplasmosis. In total, 341 pregnant women with suspected acute toxoplasmosis were systematically monitored in the Program for Control of Congenital Toxoplasmosis in Minas Gerais State, Brazil. We conducted an observational analytical-descriptive cross-sectional study and grouped according to clinical and laboratory criteria as having acute or chronic toxoplasmosis. The VIDAS TOXO IgG avidity and VIDAS TOXO IgM assays were evaluated to investigate the capacity to identify acute infection. IgG avidity showed good performance in identifying acute toxoplasmosis when the IgG avidity index was lower than or equal to 0.1. Values greater than or equal to 3.16 according to the TOXO IgM kit were associated with a greater chance of acute infection. These results may contribute to a more adequate diagnosis of acute gestational toxoplasmosis and, consequently, the avoidance of inadequate or unnecessary treatments.

The significance of antigen-antibody-binding avidity in clinical diagnosis

Immunoglobulin G (IgG) and immunoglobulin M (IgM) testing are commonly used to determine infection status. Typically, the detection of IgM indicates an acute or recent infection, while the presence of IgG alone suggests a chronic or past infection. However, relying solely on IgG and IgM antibody positivity may not be sufficient to differentiate acute from chronic infections. This limitation arises from several factors. The prolonged presence of IgM can complicate diagnostic interpretations, and false positive IgM results often arise from antibody cross-reactivity with various antigens. Additionally, IgM may remain undetectable in prematurely collected samples or in individuals who are immunocompromised, further complicating accurate diagnosis. As a result, additional diagnostic tools are required to confirm infection status. Avidity is a measure of the strength of the binding between an antigen and antibody. Avidity-based assays have been developed for various infectious agents, including toxoplasma, cytomegalovirus (CMV), SARS-CoV-2, and avian influenza, and are promising tools in clinical diagnostics. By measuring the strength of antibody binding, they offer critical insights into the maturity of the immune response. These assays are instrumental in distinguishing between acute and chronic or past infections, monitoring disease progression, and guiding treatment decisions. The development of automated platforms has optimized the testing process by enhancing efficiency and minimizing the risk of manual errors. Additionally, the recent advent of real-time biosensor immunoassays, including the label-free immunoassays (LFIA), has further amplified the capabilities of these assays. These advances have expanded the clinical applications of avidity-based assays, making them useful tools for the diagnosis and management of various infectious diseases. This review is structured around several key aspects of IgG avidity in clinical diagnosis, including: (i) a detailed exposition of the IgG affinity maturation process; (ii) a thorough discussion of the IgG avidity assays, including the recently emerged biosensor-based approaches; and (iii) an examination of the applications of IgG avidity in clinical diagnosis. This review is intended to contribute toward the development of enhanced diagnostic tools through critical assessment of the present landscape of avidity-based testing, which allows us to identify the existing knowledge gaps and highlight areas for future investigation.

[Toxoplasmosis in pregnancy: Practical Management]

The burden of congenital toxoplasmosis has become small in France today, in particular as a result of timely therapy for pregnant women, fetuses and newborns. Thus, the French screening and prevention program has been evaluated and recently confirmed despite a decline over time in the incidence of toxoplasmosis. Serological diagnosis of maternal seroconversion is usually simple but can be difficult when the first trimester test shows the presence of IgM, requiring referral to an expert laboratory. Woman with confirmed seroconversion should be referred quickly to an expert center, which will decide with her on treatment and antenatal diagnosis. Although the level of proof is moderate, there is a body of evidence in favor of active prophylactic prenatal treatment started as early as possible (ideally within 3 weeks of seroconversion) to reduce the risk of maternal-fetal transmission, as well as symptoms in children. The recommended therapies to prevent maternal-fetal transmission are: (1) spiramycin in case of maternal infection before 14 gestational weeks; (2) pyrimethamine and sulfadiazine (P-S) with folinic acid in case of maternal infection at 14 WG or more. Amniocentesis is recommended to guide prenatal and neonatal care. If fetal infection is diagnosed by PCR on amniotic fluid, therapy with P-S should be initiated as early as possible or continued in order reduce the risk of damage to the brain or eyes. Further research is required to validate new approaches to preventing congenital toxoplasmosis.

Role of Toxoplasma gondii IgG Avidity Testing in Discriminating between Acute and Chronic Toxoplasmosis in Pregnancy

Risk of mother-to-child transmission of Toxoplasma gondii during pregnancy is much greater in women who are exposed to primary T. gondii infection (toxoplasmosis) after conception compared to those who were exposed to the infection before conception. Therefore, laboratory tests that help classify recent primary toxoplasmosis are important tools for the management of pregnant women suspected to have T. gondii exposure. Detection of Toxoplasma IgM (Toxo IgM) is a sensitive indicator of primary toxoplasmosis, but the indicator specificity is low because sometimes natural IgM antibodies react with Toxoplasma antigens in the absence of the infection. Furthermore, Toxo IgM sometimes persists in blood serum for several months or years following the primary infection. In recent decades, Toxo IgG avidity assay has been used as a standard diagnostic technique for a better estimation of the infection acquisition time and identification of the primary T. gondii infection during pregnancy. Avidity is described as the aggregate strength; by which, a mixture of polyclonal IgG molecules reacts with multiple epitopes of the proteins. This parameter matures gradually within 6 months of the primary infection. A high Toxo IgG avidity index allows a recent infection (less than 4 months) to be excluded, whereas a low Toxo IgG avidity index indicates a probable recent infection with no exclusions of the older infections. This minireview is based on various aspects of T. gondii IgG avidity testing, including (i) description of avidity and basic methods used in primary studies on T. gondii IgG avidity and primary infections; (ii) importance of IgG avidity testing in pregnancy; (iii) result summary of the major studies on the use of T. gondii IgG avidity assay in pregnancy; (iv) brief explanation of the T. gondii IgG avidity values in newborns; (v) result summary of the major studies on T. gondii IgG avidity and PCR; (vi) discussion of commercially available T. gondii IgG avidity assays, including newer automated assays; and (vii) current issues and controversies in diagnosis of primary T. gondii infections in pregnancy.

Toxoplasmosis screening during pregnancy in France: Opinion of an expert panel for the CNGOF

Prenatal screening to prevent congenital toxoplasmosis as performed in France for several decades has been questioned in view of the decreasing incidence of this infection and the cost of testing. The French College of Obstetrics and Gynecology mandated a multidisciplinary panel of experts to perform a reassessment of the screening program in accordance with international good practice. In France, about 70% of pregnant women are not immune to T. gondii, and 0.2-0.25% become infected during pregnancy. The risk of maternal-fetal transmission of infection is on average 25-29% and depends greatly on the gestational age at seroconversion. In case of fetal transmission, the outcome is livebirth in 95% of cases, with latent congenital toxoplasmosis in 90% of cases and symptomatic forms in 10% of cases, of which 1/3 are severe and 2/3 moderate. Biological techniques have satisfactory performance regarding serologies for the diagnosis of maternal infections and PCR on amniotic fluid for the prenatal diagnosis of congenital toxoplasmosis. Primary prevention of toxoplasmosis is based on hygiene measures that are relatively simple, but poorly implemented. In case of maternal seroconversion, there is a strong case for prenatal prophylactic treatment as soon as possible (ideally within 3 weeks of seroconversion), spiramycin before 14 weeks of gestation (WG), and with a tendency to superiority of the pyrimethamine/sulfadiazine association over spiramycin beyond 14 W G, in order to reduce the risk of symptomatic congenital toxoplasmosis. In case of congenital toxoplasmosis, prompt initiation of treatment reduces the occurrence of cerebral signs and symptoms, as well as retinal lesions. Several medico-economic evaluations of the French toxoplasmosis screening program have been conducted including an individual cost-effectiveness approach with decision analysis which concluded on the profitability of prenatal screening as carried out in France (monthly surveillance of seronegative women, prenatal treatment in case of seroconversion, termination of pregnancy in severe forms). Though most international societies do not recommend systematic screening for mainly financial reasons, if congenital toxoplasmosis appears benign in France today, it is probably thanks to screening and the possibility of early treatment of fetuses and/or newborns. Thus, the panel recommends continuing for now the program in France for prevention of congenital toxoplasmosis.

Toxoplasma gondii-specific IgG avidity testing in pregnant women

BACKGROUND

The parasite Toxoplasma gondii can cause congenital toxoplasmosis following primary infection in a pregnant woman. It is therefore important to distinguish between recent and past infection when both T. gondii-specific IgM and IgG are detected in a single serum in pregnant women. Toxoplasma gondii-specific IgG avidity testing is an essential tool to help to date the infection. However, interpretation of its results can be complex.

OBJECTIVES

To review the benefits and limitations of T. gondii-specific avidity testing in pregnant women, to help practitioners to interpret the results and adapt the patient management.

SOURCES

PubMed search with the keywords avidity, toxoplasmosis and Toxoplasma gondii for articles published from 1989 to 2019.

CONTENT

Toxoplasma gondii-specific IgG avidity testing remains a key tool for dating a T. gondii infection in immunocompetent pregnant women. Several commercial assays are available and display comparable performances. A high avidity result obtained on a first-trimester serum sample is indicative of a past infection, which occurred before pregnancy. To date, a low avidity result must still be considered as non-informative to date the infection, although some authors suggest that very low avidity results are highly suggestive of recent infections depending on the assay. Interpretation of low or grey zone avidity results on a first-trimester serum sample, as well as any avidity result on a second-trimester or third-trimester serum sample, is more complex and requires recourse to expert toxoplasmosis laboratories.

IMPLICATIONS

Although used for about 30 years, T. gondii-specific avidity testing has scarcely evolved. The same difficulties in interpretation have persisted over the years. Some authors have proposed additional thresholds to exclude an infection of <9 months, or in contrast to confirm a recent infection. Such thresholds would be of great interest to adapt management of pregnant women and avoid unnecessary treatment; however, they need confirmation and further studies.

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Preliminary multiplex microarray IgG immunoassay for the diagnosis of toxoplasmosis and rubella

BACKGROUND

During pregnancy, toxoplasmosis and rubella can cause serious damage to the mother and the foetus through vertical transmission. Early diagnosis enables implementation of health measures aimed at preventing vertical transmission and minimising damage caused by these diseases.

OBJECTIVE

Here, we report the development of a multiplex assay for simultaneous detection of IgG antibodies produced during toxoplasmosis and rubella infection.

METHODS

This assay is based on xMap technology. Initially, by singleplex assays, we evaluated the following antigens: one Toxoplasma gondii lysate; two antigenic extracts of T. gondii (TOX8131 and TOX8122); fragments of T. gondii antigens [SAG-1 (amino acids 45-198), GRA-7 (24-100), GRA-1 (57-149), ROP-4, and MIC-3 (234-306)]; two chimeric antigens composed of fragments of SAG-1, GRA-7, and P35 (CTOX and CTOXH); and fragments of Rubella virus antigens [E-1 (157-176, 213-239, 374-390), E-2 (31-105), and C (1-123)].

FINDINGS

A multiplex assay to simultaneously diagnose toxoplasmosis and rubella was designed with the best-performing antigens in singleplex and multiplex assays, which included CTOXH, T. gondii lysate, TOX8131, E-1, and E-2. The multiplex assay showed 100% sensitivity and specificity for anti-T. gondii IgG detection and 95.6% sensitivity and 100% specificity for anti-R. virus IgG detection.

MAIN CONCLUSIONS

We found that, despite the difficulties related to developing multiplex systems, different types of antigens (extracts and recombinant proteins) can be used to develop high-performance diagnostic tests. The assay developed is suitable to screen for prior T. gondii and R. virus infections, because it is a rapid, high-throughput, low-cost alternative to the current standard diagnostic tools, which require multiple individual tests.

IgG Avidity Test in Congenital Toxoplasmosis Diagnoses in Newborns

The goal of this study was to investigate the importance of IgG avidity testing in newborns (NBs) diagnosed with early congenital toxoplasmosis. We collected samples from 88 puerperae infected by Toxoplasma gondii (T. gondii) and their NBs (48 acutely-infected puerperae (AIP) and 40 chronically-infected puerperae (CIP)), from two public maternity hospitals in Goiania city, Goias, Brazil, from 2010 to 2015. Specific anti-T. gondii IgM and IgG serum levels and IgG avidity tests were evaluated using chemiluminescence. Congenital toxoplasmosis was observed in 66.66% (n = 32) of NBs with AIP, 94.1% presenting low avidity (LA) and 51.61% presenting high avidity (HA) test results. The IgG and IgM levels of NBs with LA and their puerperae were higher in comparison with HA NBs and puerperae (p = 0.0001). The avidity tests showed 100% specificity and 50% sensitivity (p = 0.0001). NBs with LA had a 15-fold increased risk of developing congenital toxoplasmosis in comparison with HA NBs. The IgG avidity test could be used to assist in early congenital toxoplasmosis diagnoses in NBs and LA, identifying a greater probability of vertical transmission.

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

Background

Primary 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.

Methods

Retrospective 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.

Results

50% (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.

Conclusions

Half 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.

A community-based survey of Toxoplasma gondii infection among pregnant women in rural areas of Taiz governorate, Yemen: the risk of waterborne transmission

Background

Toxoplasma gondii is a zoonotic coccidian parasite causing morbidity and mortality. In Yemen, T. gondii infection has been reported among pregnant women seeking healthcare in the main cities. However, no data are available on the prevalence of T. gondii infection and its associated risk factors among pregnant women in the rural communities of the country. Thus, the present study aimed to determine the seroprevalence of T. gondii and identify its risk factors among pregnant women in the rural communities of Taiz governorate, Yemen.

Methods

A total of 359 pregnant women living in the rural communities of Taiz governorate were enrolled in this study by house-to-house visits. Data were collected using a pre-designed questionnaire, and blood samples were collected and tested for the detection of anti- T. gondii IgM and IgG antibodies by enzyme-linked immunosorbent assay.

Results

The prevalence of T. gondii infection among pregnant women in this study was 46.2% (166/359). Bivariate analysis identified the age of  ≥ 30 years (odds ratio [OR] = 1.7; 95% confidence interval [CI] = 1.09–2.65, P = 0.019) and unimproved water sources (OR = 2.2; 95% CI = 1.10–4.55, P = 0.023) as factors associated with T. gondii infection among pregnant women. The multivariable analysis, however, identified unimproved water sources as an independent risk factor (adjusted OR = 2.4; 95% CI = 1.16–5.0, P = 0.018) associated with T. gondii infection among pregnant women.

Conclusions

Pregnant women in the rural communities of Taiz, Yemen are at high risk of contracting T. gondii infection. Unimproved water sources (wells, water streams and water tanks) are significantly associated with T. gondii infection and should be considered in prevention and control strategies, especially among pregnant women.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0243-0) contains supplementary material, which is available to authorized users.

Relevance of and New Developments in Serology for Toxoplasmosis

Toxoplasmosis is a widespread parasitic disease caused by the intracellular parasite Toxoplasma gondii with a wide spectrum of clinical outcomes. The biological diagnosis of toxoplasmosis is often difficult and of paramount importance because clinical features are not sufficient to discriminate between toxoplasmosis and other illnesses. Serological tests are the most widely used biological tools for the diagnosis of toxoplasmosis worldwide. This review focuses on the crucial role of serology in providing answers to the most important questions related to the epidemiology and diagnosis of toxoplasmosis in human pathology. Notwithstanding their undeniable importance, serological tools need to be continuously improved and the interpretation of the ensuing results remains complex in many circumstances.

Persistent Low Toxoplasma IgG Avidity Is Common in Pregnancy: Experience from Antenatal Testing in Norway

The parasite Toxoplasma gondii might harm the fetus if a woman is infected during pregnancy. IgG seroconversion and significant increase in IgG antibody amount in pregnancy indicates maternal infection. Presence of toxoplasma immunoglobulin M (IgM), immunoglobulin G (IgG) and low IgG avidity in a single serum sample indicates possible maternal infection, but positive toxoplasma IgM and low IgG avidity may persist for months and even years. We aimed to evaluate avidity development during pregnancy in a retrospective study. Serial blood samples from 176 pregnant women admitted to Oslo University Hospital 1993–2013 for amniocentesis because of suspected toxoplasma infection were included. Data were obtained from journals and laboratory records. The avidity method used was based on Platelia Toxo IgG assay. Mean maternal age at first serology was 29.9 years (SD 5.2, range 18–42). In 37 (21%) women only the avidity increased from low to high in < 3 months. In 139 (79%) the IgG avidity remained below the high threshold ≥ 3 months and within this group 74 (42%) women had stable low IgG avidity during the observation period. Median gestational age at first test was 10.6 weeks (range 4.6–28.7). Fetal infection was detected in four children, but none among children whose mother had stable low IgG avidity. The first antenatal toxoplasma serology should ideally be collected in early pregnancy and if stable values of toxoplasma IgM and low IgG-avidity are detected in a second sample after three to four weeks, the need for amniocentesis can be questioned.

Multicenter evaluation of the Elecsys Toxo IgG and IgM tests for the diagnosis of infection with Toxoplasma gondii

Detection of IgG and IgM antibodies is commonly performed for the diagnosis of infection with Toxoplasma gondii. We determined the accuracy of the Elecsys Toxo IgG and IgM test at four European laboratories compared to local reference methods. Coefficients of variation for reproducibility ranged from 1.0 to 6.5% for IgG and from 0.8 to 3.2% for IgM. Seroconversion panels revealed high overall concordance with the reference tests. The Elecsys test detected IgG antibodies earlier than the Cobas Core IgG test in 19 of 47 panels; persisting IgM antibodies were observed in the VIDAS but not the Elecsys test in five of 47 panels. In 31.4% of latent stage sera with persistent IgM antibodies (positive LIASON IgM), the Elecsys IgM test gave negative results indicating increased "clinical" specificity. Sensitivity and specificity of the Elecsys IgG assay ranged from 99.45 to 100% and 87.50-99.80%, respectively, and 91.11-95.74 and 98.45-99.79% for the Elecsys IgM assay, respectively. In conclusion, excellent reproducibility and accuracy make the Elecsys Toxo G and M tests highly suitable for the detection of anti-T. gondii IgG and IgM antibodies. The lower detection rates for persistent IgM in the Elecsys IgM test increase "clinical" specificity and decrease the need for follow-up testing.

Seroprevalence of Toxoplasma, Rubella, and Cytomegalovirus among pregnant women in Van

OBJECTIVE

To determine the seroprevalence of anti-Toxoplasma, anti-Rubella, and anti-Cytomegalovirus (CMV) antibodies among pregnant women receiving prenatal care at Van Training and Research Hospital.

MATERIALS AND METHODS

In developing countries, various infectious agents encountered in the gestational period are important because they influence both maternal and fetal health. Among these, Toxoplasma gondii, Rubella and CMV are quite prevalent. In the present study, anti-Toxoplasma, anti-Rubella and anti-CMV antibodies were analyzed in the serum samples obtained from women receiving prenatal care at Van Training and Research Hospital between June 2012 and July 2013, and positive serum samples were retrospectively evaluated. Anti-Toxoplasma, anti-Rubella and anti-CMV antibodies were analyzed using ELISA with Cobas 4000 e411 (Roche, Germany) and Architect i2000SR (Abbott Diagnostics, Germany) analyzers.

RESULTS

Over the course of the study period, the results of a total of 9809 patients were investigated in terms of anti-Toxoplasma, anti-Rubella, and anti-CMV antibodies. Anti-Toxoplasma, anti-Rubella, and anti-CMV IgM and IgG antibody positivity rates were 1.1%, 0.5% and 2.6%, and 37.6%, 86.5% and 100%, respectively.

CONCLUSION

Anti-Toxoplasma IgG antibody positivity rates determined in the present study were lower as compared with the results of the other studies reported from Turkey. However, CMV IgM and IgG antibody positivity rates were be higher as compared with those reported in the literature.

Efficient duplex solid-phase fluorescent assay (dFISA) for the simultaneous detection of specific anti-T. gondii IgG and IgM due to refined conjugates

Toxoplasma gondii infections are very common, causing occasional central nervous system and eye diseases, and must be screened in prenatal care for efficient therapy. Here, we developed a duplex solid-phase fluorescent assay (dFISA) for the simultaneous detection of anti-T. gondii IgG and IgM antibodies in prenatal care screening for toxoplasmosis. Assays using commercially available ion-exchange purified conjugates yielded poor results and high background fluorescence. Same-well IgG/IgM dFISA with refined conjugates was used to test 140 samples from university students, 120 samples from pregnant women and 24 samples from adult volunteers at a large public hospital. We found that dFISA offers high concordance, specificity and reproducibility for IgG (Kappa=0.883) and IgM (Kappa=0.918), which is useful in high-throughput applications for antenatal care.

Comparison of the Vidas system and two recent fully automated assays for diagnosis and follow-up of toxoplasmosis in pregnant women and newborns

Serological testing to detect toxoplasmosis is of major importance to avoid the possible effects of the disease in newborns. This study assessed anti-Toxoplasma IgG and IgM with the Vidas (bioMérieux), Architect (Abbott), and Liaison (DiaSorin) systems in 631 sera from pregnant women and newborns as well as anti-Toxoplasma IgG avidity with these three systems on 54 sera from pregnant women with positive IgG and IgM. The IgG and IgM results were in agreement in, respectively, 95.2% and 98.3% (Vidas versus Architect) and 96.9% and 95.3% (Vidas versus Liaison) of the samples. Specificities were excellent for all the assays, while Vidas sensitivities ranged (depending on the classification of gray zone results) from 93.8 to 98.4% for IgG (Architect, 84.4 to 93.8%; Liaison, 93.8%) and from 81.8 to 90.9% for IgM (Architect, 63.6%; Liaison, 81.8 to 90.9%). In seroconversion sequences, IgMs were generally detected simultaneously by the three assays, while Architect was the earliest assay to detect IgG. In noninfected children, maternally transmitted IgGs were detected for a longer time with Architect than with the other systems. IgMs were positive in only one infected child with the Vidas and Liaison systems. Significantly more sera were classified in the high-avidity category with Vidas than with Architect. This evaluation shows similar performances for Vidas and more recent systems. The Vidas system adequately detects toxoplasmosis in pregnant women and newborns. This system fits the needs of laboratories working on small routine series for first-line testing as well as expert laboratories, due to a high specificity and a powerful avidity test.