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Objective The purpose of the present study is to standardize and evaluate the use of the immunoglobulin G (IgG) antibody avidity test on blood samples from newborns collected on filter paper to perform the heel test aiming at its implementation in ongoing programs. Methods Blood samples from newborns were collected on filter paper simultaneously with the heel prick test. All samples were subjected to immunoglobulin M IgM and IgG enzyme-linked immunosorbent assays (ELISA). Peripheral blood was collected again in the traditional way and on filter paper from newborns with high IgG levels (33). Three types of techniques were performed, the standard for measuring IgG in serum, adapted for filter paper and the technique of IgG avidity in serum and on filter paper. The results of the avidity test were classified according to the Rahbari protocol. Results Among the 177 samples, 17 were collected in duplicate from the same child, 1 of peripheral blood and 1 on filter paper. In this analysis, 1 (5.88%) of the 17 samples collected in duplicate also exhibited low IgG avidity, suggesting congenital infection. In addition, the results obtained from serum and filter paper were in agreement, that is, 16 (94.12%) samples presented high avidity, with 100% agreement between the results obtained from serum and from filter paper. Conclusion The results of the present study indicate that the avidity test may be another valuable method for the diagnosis of congenital toxoplasmosis in newborns. Resumo Objetivo O objetivo do presente estudo é padronizar e avaliar a utilização do teste de avidez de anticorpos imunoglobulina G (IgG) em amostras de sangue de recémnascidos (RNs) coletadas em papel filtro para a realização do teste do pezinho visando a implementação nos programas já vigentes. Métodos Foram coletadas amostras de sangue de recém-nascidos em papel filtro simultaneamente ao teste do pezinho. Em todas as amostras, foram realizados os testes imunoenzimáticos (ELISA) imunoglobulina M (IgM) e IgG. Dos RNs que apresentaram altos índices de IgG (33), foi novamente coletado sangue periférico da forma tradicional e em papel filtro. Foram realizadas técnicas padrão para a dosagem de IgG em soro, adaptadas para papel filtro, e a técnica de avidez de IgG em soro e em papel filtro. Os valores obtidos para o teste de avidez foram classificados de acordo com o protocolo de Rahbari. Resultados Dentre as 177 recoletas, em 17 amostras foi realizada a coleta simultânea de sangue periférico e papel filtro da mesma criança. Nesta análise, 1 (5,88%) das 17 amostras coletadas em duplicata obteve também baixa avidez de IgG, sugerindo infecção congênita da criança, e houve concordância entre os resultados obtidos em soro e em papel filtro: 16 (94,12%) das amostras apresentaram alta avidez, com concordância de 100% entre os resultados obtidos em soro e em papel filtro. Conclusão Os dados do presente trabalho evidenciam que o teste de avidez poderá ser mais um método valioso a ser utilizado no diagnóstico da toxoplasmose congênita em RNs.

This study intended to evaluate the seroprevalence of anti-Toxoplasma IgG and IgM antibodies in the sera of 630 women at childbearing age, and to link the outcomes with some risk factors. The enrolled women visited Zakho Maternity Hospital from July 2018 to July 2019. Their ages ranged from 15 to 45 years. All samples were examined using ELISA to detect immunoglobulin G and M, in addition to performing IgG Avidity test for seropositive pregnant women. The differences between seropositivity and age was significant (p

Objectives The aim of the current study was to assess prevalence of Toxoplasma infection and its associated risk factors in women of childbearing-age in central Iran. Results Of 400 serum samples assessed for anti-T. gondii antibodies, 81 (20.25%) samples were positive for anti-T. gondii antibodies, including 74 positive samples (91.3%) for anti-T. gondii IgG and seven positive samples (8.7%) for IgG and IgM. Of seven IgG and IgM positive samples, five and two samples were high and low in IgG avidity, respectively. Based on PCR analysis, Toxoplasma infection was detected in one sample with anti-T. gondii IgM and low IgG avidity. The Chi-square test showed significant correlations of T. gondii seropositivity with history of undercooked meat consumption and contacts with cats (p T. gondii infection. Furthermore, recently acquired Toxoplasma infection was found using IgG avidity and PCR assays among women of childbearing-age in the study area, which would increase the risk of their fetus becoming infected. Educational program and antenatal screening of childbearing-age women for T. gondii infection may be important primary prevention strategies and help reduce the risk of congenital toxoplasmosis in this population.

Background: When a pregnant woman contracts Toxoplasma gondii ( T. gondii ) infection during pregnancy, it may be vertically transmitted to the foetus. Information on the incidence of congenital toxoplasmosis (CT) in developing countries is scarce. Most studies focus on the seroprevalence of T. gondii infection among pregnant women. This study aimed to determine the seroprevalence of T. gondii infection among pregnant women attending public antenatal care in Windhoek, Namibia, in 2016. Methods: In this descriptive study, 344 urban pregnant women attending public antenatal care were voluntarily enrolled in the study. Seroprevalence of anti- T. gondii Immunoglobulin G (IgG) was determined by automated immunoassay. Samples with a positive T. gondii IgG result were tested for T. gondii Immunoglobulin M (IgM) and specific IgG avidity by using an enzyme-linked immunosorbent assay (ELISA) test. A questionnaire captured demographic data and exposure to risk factors. Data were analysed using Statistical Package for the Social Sciences (SPSS) and R. Results: Anti- T. gondii IgG was found in nine (2.61%) pregnant women. There was no association of anti- T. gondii IgG with demographic characteristics or exposure to risk factors.Anti- T. gondii IgM was positive in one (0.3%) woman, while three (0.9%) women had borderline anti- T. gondii IgM results. Specific IgG avidity was low, equivocal and high in 0%, 33% and 67% of seropositive pregnant women, respectively. Conclusion: Seroprevalence of anti- T. gondii IgG is much lower in Namibia than is reported in other developing countries. Investigation into specific IgM seropositivity and IgG avidity showed that pregnant women in the central region of Namibia are at low risk of vertical transmission and development of CT.

Human parvovirus B19, human cytomegalovirus, and Toxoplasma gondii are ubiquitous pathogens. Their infections are often asymptomatic or mild in the general population yet may be transmitted from mother to fetus during pregnancy. Maternal infections by these pathogens can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the infection time; hence, it is important to determine when a pregnant woman has acquired the infection. In this study, we developed new diagnostic approaches for the timing of infections by three pathogens. All the new assays appeared to be highly sensitive and specific, providing powerful tools for medical diagnosis., Human parvovirus B19 (here B19), human cytomegalovirus (HCMV), and Toxoplasma gondii infections during pregnancy can lead to severe complications. While traditional diagnosis of infections is mostly confined to one pathogen at a time, a multiplex array is a feasible alternative to improve diagnostic management and cost-efficiency. In the present study, for these three pathogens, we developed microsphere-based suspension immunoassays (SIAs) in multiplex and monoplex formats for the detection of antimicrobial IgM antibodies as well as corresponding chaotrope-based IgG avidity SIAs. We determined the diagnostic performances of the SIAs versus in-house and commercial reference assays using a panel of 318 serum samples from well-characterized clinical cohorts. All the newly developed assays exhibited excellent performance compared to the corresponding high-quality reference methods. The positive and negative percent agreements of the IgM SIAs in comparison with reference methods were 95 to 100% and 98 to 100%, and those of the IgG avidity SIAs were 92 to 100% and 95 to 100%, respectively. Kappa efficiency values between the SIAs and the corresponding reference assays were 0.91 to 1. Furthermore, with another panel comprising 391 clinical samples from individuals with primary infection by B19, HCMV, or T. gondii, the IgM SIAs were highly sensitive for the detection of acute infections, and the IgG avidity SIAs were highly specific for the separation of primary infections from past immunity. Altogether, the strategy of IgM multiplex screening followed by IgG avidity reflex testing can provide high-throughput and accurate means for the detection and stage determination of B19, HCMV, and T. gondii infections. IMPORTANCE Human parvovirus B19, human cytomegalovirus, and Toxoplasma gondii are ubiquitous pathogens. Their infections are often asymptomatic or mild in the general population yet may be transmitted from mother to fetus during pregnancy. Maternal infections by these pathogens can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the infection time; hence, it is important to determine when a pregnant woman has acquired the infection. In this study, we developed new diagnostic approaches for the timing of infections by three pathogens. All the new assays appeared to be highly sensitive and specific, providing powerful tools for medical diagnosis.

International audience; 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

Background: We aimed to evaluate the diagnosis of acute toxoplasmosis by IgG avidity test in pregnant women. Methods: In this cross-sectional study, 250 blood samples were collected from pregnant women with the first month of their pregnancy referring to health centers of University in Mashhad during 2016. Samples were centrifuged at 3000 rpm for 5 min for separation of serum and were kept in the -20 until use. To detection of acute and chronic toxoplasmosis, anti-Toxoplasma antibodies (IgG and IgM, and IgG avidity tests were performed using ELISA. Then, data analyzed using SPSS software by Frequency, Pearson Chi-Square, Likelihood Ratio, and Exact tests. And P-value

Objectives Congenital toxoplasmosis (CT) affects one to ten fetuses per 10 000 live newborns in western countries. Without knowing pre-conception serostatus, it is hard to date the infection when anti-Toxoplasma IgG and IgM antibodies are positive at first screening. Although a high IgG avidity index (AI) in the first trimester excludes CT, the same cannot be said of intermediate and low AI. The aim of this study was to estimate the risk of CT when intermediate or low AI is detected in the first trimester of pregnancy. Methods Our observational retrospective study enrolled women with positive anti-Toxoplasma IgG and IgM, and low/intermediate AI in the first trimester of gestation seen at two reference centres in northern Italy between 2006 and 2015. All women received spiramycin. When requested by women, a sample of fluid obtained through amniocentesis was tested with a commercial real-time PCR. CT was defined by positive PCR result confirmed on aborted materials or by newborn follow up. Results Overall, 778 first-trimester pregnant women were included; AI was low in 532/778 (68%) and intermediate in 246/778 (32%). Amniocenteses were performed in 528/778 (67.9%), with no fetal loss. In all, 19/778 (2.4%) miscarriages and 15/778 (1.9%) pregnancy terminations were recorded; 9/778 (1.6%) were lost to follow up. In two women, PCR on amniotic fluid was positive, but CT was confirmed in only 1/747 cases (0.13%, 95% CI 0.02%–0.75%). Conclusion In our study, the risk of CT was much lower than anticipated. These data must be considered when counselling these women.

Background: The aim of this study was to determine the level of knowledge and practices about toxoplasmosis in a sample of clinical laboratory professionals in Mexico. Methods: 192 clinical laboratory professionals were surveyed. They were asked about (1) Toxoplasma gondii; (2) clinical manifestations, diagnosis, treatment, and epidemiology of toxoplasmosis; and (3) their practices with respect to toxoplasmosis. Results: The range of animals infected by T. gondii was known by 44.8% of participants. Clinical aspects of toxoplasmosis were known by up to 44.3% of subjects. Correct answers about the interpretation of serological markers of T. gondii infection were provided by up to 32.8% of participants. A minority (32.2%) of participants knew about a high number of false positive results of anti-T. gondii IgM antibody tests. Most participants (90.1%) did not know what the anti-T. gondii IgG avidity test was. Up to 55.7% of participants provided incorrect answers about the interpretation of serology tests for the treatment of pregnant women. Common routes of T. gondii infection were known by

A maternal Toxoplasma gondii infection during pregnancy is a risk for congenital infection through maternal-fetal transplacental transmission. Estimation of the date of infection is of the utmost importance for management and treatment recommendations. In this setting, IgG avidity has been shown to be useful as high avidity rules out an infection dating less than 4 months. The estimated date of infection can also be obtained by the ratio of T. gondii IgG titers measured by the Vidas (bioMerieux) assay versus T. gondii IgG titers measured by the Architect (Abbott Laboratories) test, together with T. gondii IgM and IgA antibody responses. In this study, using 117 serum samples from pregnant women, we compared the IgG avidity values obtained by Architect and Vidas with the presumed date of T. gondii infection established by the T. gondii IgG ratio of IgG Vidas and IgG Architect plus the IgM and IgA results. To date, IgG avidity Vidas seems to exhibit better performance than Architect. For both assays, gray zone results were most likely obtained from patients infected more than 4 months before sampling. These data should be taken into account for a possible reconsideration of the interpretation of avidity results in the gray zone.

Herein, we determined the seroprevalence, seroconversion, and risk factors associated with Toxoplasma gondii (T. gondii) infection among pregnant women in Taipei, Taiwan. Pregnant women attending antenatal consultation in a Taipei medical center were invited, and 104 women completed a self-administered structured questionnaire. Venous blood samples were collected during the first and third trimester after consent was obtained. Serum IgG and IgM antibodies (Abs) as well as IgG avidity were analyzed using an enzyme-linked fluorescent assay. Of the samples collected in the first trimester, seven were seropositive for IgG Abs and one was seropositive for IgG + IgM Abs with a borderline avidity index, resulting in an overall seroprevalence of 7.7%. No statistically significant association was found between toxoplasmosis and age, pregnancy history, or any risk factors. Seroconversion was not detected from paired sera between the first and third trimesters. Pregnant women with senior high school education level or those who claimed to knowing Toxoplasma exhibited a significantly higher seroprevalence than those with bachelor degree (P = 0.05) or those who claimed not to have this knowledge (P = 0.05). Therefore, failure to understand the importance of T. gondii infection and the prevention measures resulted in the development of toxoplasmosis among these women.

A população estudada foi composta por 2.126 gestantes atendidas em unidades do Sistema Único de Saúde da região noroeste do Estado do Rio Grande do Sul. Após o screening sorológico inicial ocorreu o acompanhamento das gestantes, durante o pré-natal, e de seus bebês. Foram realizadas dosagens de IgG, IgM, IgA, Avidez de IgG, inoculação em camundongos, PCR e coleta de placenta e de cordões umbilicais para realizar a técnica de imuno-histoquímica além de avaliações clínicas. Das gestantes avaliadas, 74,5% eram IgG reagentes e 3,6% IgM reagentes. Nas avaliações oftalmológicas, foi observada lesão em dez gestantes e uma criança apresentou lesões oftalmológicas e calcificações cerebrais. A presença de IgM específico anti- T.gondii, durante toda a gestação não caracterizou a fase aguda recente da infecção, fazendo-se necessária a realização de testes complementares. Ressalta-se a importância do acompanhamento de neonatos de mães com sorologia compatível com a infecção mesmo sem sinais e sintomas sugestivos de toxoplasmose congênita. This study followed up 2,126 pregnant women cared for at SUS day-care clinics (Public Health Insurance System) of the northwest of the State of Rio Grande do Sul, Brazil. After serological screening we performed a follow up of all pregnant women and their babies. Serologic tests included: IgG, IgM, IgA and IgG avidity levels, mice inoculation and polymerase chain reaction (PCR) also placentas and umbilical materials were tested using immunoperoxidase as well as clinical evaluation. Of all the pregnant women screened, 74.5% were reactive to toxoplasmosis, and 3.6% presented IgM seropositivity. At ophthalmic evaluation ten women had ocular lesions and one infant presented eye lesions and brain calcification. The presence of anti-T.gondii specific IgM throughout the entire pregnancy did not characterize acute phase infection, for this, complementary tests were necessary. The importance is underscored for attendance of the newborn of mothers presenting serology compatible with this infection even in the absence of signs and symptoms of congenital toxoplasmosis.

Background: Acute toxoplasmosis in pregnant women presents a high risk of Toxoplasma transmission to the fetus. Early diagnosis is difficult, especially when serological testing for IgG/IgM antibodies fail to differentiate between a recent and a past infection. In this case, we rely on IgG avidity or PCR assays. Objectives: The aim of this study was to compare conventional ELISA and IgG avidity, with PCR using B1 and P30 primers for the early diagnosis of toxoplasmosis in pregnant women. Methods: Sera were collected from 143 pregnant women and measured by ELISA for anti- Toxoplasma IgG, IgM, IgA and IgG avidity. DNA was extracted from 57 peripheral blood and 14 amniotic fluid samples for PCR amplification. Results: A total of 57 out 143 women were seropositive: 30 (52.6%) were IgG+/IgM- and 27 (43.8%) were IgG+/IgM+; IgA antibodies were positive in 7 (12.2%) cases. IgG avidity was low in 9 women suggesting an acute infection; 3 women presented an intermediate avidity. PCR detected Toxoplasma DNA in 9 women presenting low avidity and was negative for the intermediate avidity cases. Conclusion: PCR combined to avidity IgG performed better than ELISA IgG, IgM and/or IgA assays alone. PCR was useful in the case of intermediate avidity. Keywords: Toxoplasmosis, pregnant women, serology, IgG avidity, PCR

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.

A brief report on the nature and epidemiology ofT. gondiiinfection is firstly presented. The importance of the specific IgG avidity test and polymerase chain reaction (PCR) for toxoplasmosis is discussed, along with their significance and importance as auxiliary methods for determining the most likely time for the initial infection by this coccidian and for defining the therapeutic strategy. Lastly, practical comments are made in relation to the classical therapeutic regimens, with special attention to the indications for fetal treatment, when this is necessary.

Serological screening for maternal Toxoplasma infections in pregnancy has been questioned recently. We analyze some diagnostic difficulties for routine laboratories, poor public health guidance of existing screening programs, and their mutual worsening impact on the efficacy of the programs and on toxoplasmosis research. False positive screening tests may be more likely than true maternal Toxoplasma infections and diagnosis often depends on confirmatory testing in experienced reference laboratories. Apart from clear seroconversions, any marker to assign the time point of infection to the ongoing pregnancy (IgM, IgG avidity, etc.) suffers from important limitations. With poor screening compliance, many screening alerts come from first serum samples in pregnancy that are cumbersome to test, while seroconversions are seldom observed due to missing follow-up samples in late pregnancy. From a public health perspective, inadequate epidemiological assessment and research, insufficient quality control for compliance and little consideration of diagnostic peculiarities for the design of more effective preventive programs has resulted in poor performance. These shortcomings have contributed to the present doubts about preventive Toxoplasma screening in pregnancy. We recommend that a team of public health decision makers, epidemiologists and experts from toxoplasmosis reference laboratories reevaluates the existing activities in a given country to build up a well-designed preventive program that avoids these drawbacks.

O objetivo deste estudo foi avaliar o valor preditivo do teste de avidez de IgG no diagnóstico precoce da toxoplasmose congênita (TC) no recém-nascido (RN). O grupo de estudo foi constituído por 68 pares de puérperas e seus RN, sendo 43 com toxoplasmose aguda durante a gravidez e 25 com IgM negativo para Toxoplasma gondii (grupo controle). As pacientes pariram os RN na Maternidade do Hospital das Clínicas da Universidade Federal de Goiás. Foram avaliados os níveis séricos de IgM e IgG anti-T. gondii e avidez de IgG. Os RN do grupo de estudo foram divididos em RN com baixa avidez (BA) e RN com elevada avidez (EA). Foi verificada a concordância do teste de avidez dos RN e das puérperas. A infecção pelo T. gondii foi observada em 94,1% dos RN com BA e 42,3% dos RN com EA. Os níveis de IgG e de IgM dos RN com BA e de suas puérperas infectadas foram elevados e apresentaram diferença quando comparados com os RN com EA (p=0,0001) e os RN não infectados (p=0,0001) e suas respectivas puérperas. A sintomatologia da TC foi observada em 56% dos RN com BA e em 18% dos RN com EA. Nossos dados mostram que RN com BA apresentaram aumento de IgM e IgG e sintomas severos da TC. Assim, o teste de avidez poderia ser utilizado em conjunto com a detecção de IgM e IgG no diagnóstico precoce da TC no RN.

Detection and treatment of acute toxoplasmosis during pregnancy can avoid severe disease of the fetus. In this context, assessment of anti-ToxoplasmaIgG avidity has been shown to exclude recent infection. The Elecsys Toxo IgG and IgM assays (Roche Diagnostics) have been validated for screening pregnant women and a new assay, Elecsys Toxo IgG Avidity, was recently developed. Our aims were to investigate the performance characteristics of this new avidity assay and explore whether additional information can be provided by avidity assays. The Elecsys assay was compared with the Vidas (bioMérieux) and Architect (Abbott) Avidity assays using two sets of serum samples (n= 291 andn= 255). The rate of general agreement between the Elecsys and Vidas assays was 74%, and that between the Elecsys and Architect assays was 83%. For 11% of the serum samples, avidity was high with the Vidas assay and within the gray zone with the Elecsys assay. None of the assays detected high-avidity antibodies in serum taken 90% were exclusively reported in sera taken >9 months after infection by the Elecsys and Architect assays. Almost all avidities of

The seroprevalence of toxoplasmosis in 832 pregnant women in Miracema, Rio de Janeiro, was determined and 75.1% (625) and 2.0% (17) were anti-Toxoplasma gondii IgG and IgM positive, respectively. Out of the 17 IgM positive pregnant women, only one had low avidity IgG corresponding to the acute phase of the infection. All the other women presented with high avidity IgG and also presented with residual IgM anti-T. gondii. Of this sample, 106 received home visits (this includes 11 family nuclei of pregnant women with residual IgM anti-T. gondii, 68 nuclei of only IgG positive pregnant women and 27 nuclei of pregnant women with no antibodies to anti-T. gondii), resulting in 267 individuals visited. Out of these 267 individuals, 21 were positive for IgG and IgM anti-T. gondii and were candidates for the IgG avidity test. All of them presented with high avidity IgG and residual IgM. Five of these IgM+ individuals were (5/238; 2.1%) relatives of IgM negative pregnant women. The other 16 (16/29; 55.2%) were relatives of IgM+ pregnant women who were positive for residual IgM anti-T. gondii. This association was statistically significant (p = 0.0000). The analysis presented herein raises questions regarding the presence of residual IgM anti-T. gondii such as genetic determinants or even constant antigenic stimuli for the same family cluster.

A comparative evaluation of 384 selected sera was performed using the Beckman Coulter Access and Abbott Axsym Toxo-IgG assays. The Axsym assay yields positive early results following infection, while the Access assay gives higher titres during chronic infection. The ratio between the two complementary tests, Axsym Toxo-IgG/Access Toxo-IgG (Ax/Ac), was compared with the Vidas anti-Toxoplasma IgG avidity index (AI). The Ax/Ac ratio decreased progressively as the time between infection and sampling increased. The mean Ax/Ac values (+/-SE) were 2.50 (+/-0.26), 2.14 (+/-0.13), 2.33 (+/-0.22), 1.34 (+/-0.09), 1.32 (+/-0.10), 0.92 (+/-0.08) and 0.74 (+/-0.07) for groups of sera sampled at 1, 2, 3, 4-5, 6-8, 9-12 and 13-24 months, respectively, after infection in pregnant women. These values were much smaller for cases with chronic infection (24 months), i.e., 0.56 (+/-0.03), 0.44 (+/-0.04) and 0.53 (+/-0.04), respectively, for pregnant women and immunodepressed patients with and without reactivation. Taking a ratio of 1 as a threshold for recent infection, the patients in the groups sampled at 1, 2 and 3 months had Ax/Ac ratios1 in 49/50 (98%), 53/55 (96.4%) and 36/36 (100%) cases, respectively. Thus, an Ax/Ac ratio of1 in serum from a pregnant woman allows a recent infection (3 months) to be excluded. This technique has the advantage of yielding positive results that develop much more rapidly than the AI, thereby helping to reassure large numbers of pregnant women and avoiding costly and unnecessary prophylactic treatment and follow-up.

AcuteToxoplasma gondiiinfection in early pregnancy carries the risk of transmitting the infection to the fetus with serious sequelae. However, serological testing for IgG/IgM anti-Toxoplasmaantibodies may fail to differentiate between a recent and past infection. Two hundred and twenty-four Kuwaiti women in their first trimester were screened for IgG/IgM antibodies by the Vitek Immuno Diagnostic Assay System (VIDAS) and VIDAS IgG-avidity tests. On serological screening, 119 (53.1 %) women were positive for IgG antibodies and 31 (13.8 %) for IgM antibodies. Nine of the IgM-positive and 7 IgM-negative women had low-avidity antibodies. However, the IgG-avidity test detected low-avidity antibodies only in 9 (29 %) of the 31 IgM-positive women, suggesting a recent infection; 19 (61.3 %) women had high-avidity antibodies, indicating that the infection was acquired in the distant past. Based on IgM serology alone, at least 31 IgM-positive women may have been wrongly labelled as having acuteToxoplasmainfection thus warranting appropriate therapeutic intervention. All the 19 IgM-positive women with high-avidity antibodies were confirmed negative forToxoplasmaDNA on PCR analysis. Compared with PCR analysis, the VIDAS avidity test was a helpful tool for the diagnosis of recentToxoplasmainfection in IgM-negative women with low-avidity antibodies and IgM-positive women with high-avidity antibodies; the specificity was >85 –100 %. It is concluded that the VIDAS avidity test when used in combination with VIDAS IgG/IgM tests is a valuable assay for the exclusion of ongoing or recently acquiredT. gondiiinfection in pregnant women in their first trimester and that it decreases significantly the necessity for follow-up testing and unnecessary therapeutic intervention.

Traditional serological techniques have some limitations in evaluating the duration of Toxoplasma gondii infection in pregnant women, patients with lymphadenopathy, and older children suspected of having congenital toxoplasmosis. In these three groups of patients, two variants of T. gondii immunoglobulin G (IgG) avidity tests were used: an EIA Kit (Labsystems) and a noncommercial enzyme-linked immunosorbent assay specially elaborated in the laboratory. The avidity of specific IgG in sera from 23 patients with a known recently acquired infection (mainly pregnant women) was low (less than 30%), whereas that in sera from 19 patients with toxoplasmic lymphadenopathy of 3 weeks to 6 months in duration (mean, 8.3 weeks) covered a large range (between 0.2 and 57.8%; mean, 25.7%); high avidity results were observed for 10 of 19 patients (52.6%). The large range of IgG avidity in patients with toxoplasmic lymphadenopathy suggests various durations of infection in these patients, with a tendency for a chronic phase of toxoplasmosis. According to the avidity marker, five patients with lymphadenopathy for less than 3 months did not have a recent Toxoplasma infection. In 6 of 19 patients with lymphadenopathy (31.6%), low IgG avidity values persisted until 5 months after the first serological examination. In all four patients with a documented chronic course of Toxoplasma infection (6 months to 8 years after the first positive serology), high IgG avidity values were observed. Among sera from 10 children and young immunocompetent adults suspected of having ocular reactivation of congenital toxoplasmosis, all had high IgG avidity values (over 40%), suggesting congenitally acquired ocular infection rather than noncongenital infection. In conclusion, the avidity of IgG is a valuable marker of recent toxoplasmosis in pregnant women, suggests the duration of invasion in patients with lymphadenopathy, and may be helpful for differentiation between reactivation of congenital infection and recently acquired ocular toxoplasmosis in immunocompetent patients. A low IgG avidity does not always identify a recent case of toxoplasmosis, but a high IgG avidity can exclude primary infections of less than 5 months’ duration.

AIMS: To verify the perinatal outcomes in pregnant women with acute toxoplasmosis, and to determine if there was association between the results of Toxoplasma gondii-specific IgG avidity test and the presence or absence of fetal/neonatal infection. METHODS: A cross-sectional study included pregnant women with serological diagnosis of acute toxoplasmosis (presenting a positive Toxoplasma gondii-specific IgM test) attended at the outpatient unit for high-risk pregnancy of the Faculty of Medicine, Federal University of Mato Grosso do Sul, Brazil, in the period from November 2002 to November 2007. Test results demonstrating IgG avidity index above 30% were considered high avidity, while values below 30% were considered low avidity. Fetal and/or neonatal infection was defined by positive result for the polymerase chain reaction in amniotic fluid, or by a positive Toxoplasma gondii-specific IgM test in the newborn's serum. RESULTS: Considering all pregnant women referred to the outpatient unit for high-risk pregnancy in the period of study, frequency of pregnant women with positive Toxoplasma gondii-specific IgM was 10.8% (176/1.634). The rate of congenital infection in these patients was 4% (7/176). The IgG avidity test was performed in 162 patients (92% of the 176 pregnant women with positive IgM), and the avidity was high in 144 (88.9%). There was an association (p=0.003) between high avidity and no fetal/neonatal toxoplasmosis in our sample, with a prevalence ratio of 13.4 (confidence interval [CI] 95% 2.2-86.6). The positive predictive value of the avidity test (probability of congenital infection with a low avidity) was 22% (95% 6%-47%), while the negative predictive value (probability of absence of congenital infection with a high avidity) was 98% (95% CI 94% -99%). CONCLUSIONS: In this study the rate of congenital infection in pregnant women diagnosed with acute toxoplasmosis was 4%. In pregnant women with positive Toxoplasma gondii-specific IgM, results of Toxoplasma gondii-specific IgG avidity test were associated with the presence or absence of congenital infection, with a high negative predictive value (no fetal/neonatal infection when avidity was high).