Multicenter evaluation of strategies for serodiagnosis of primary infection with Toxoplasma gondii.

The diagnostic performance of single-serum assays for toxoplasma-specific immunoglobulin (Ig)M. IgA. IgG, and IgE antibodies and of different combinations of such antibody assays in 20 European reference centers was assessed. A panel of 276 sera, of which 73 came from patients who seroconverted within 3 months (acute infection), 49 from patients who had seroconverted 3-12 months earlier (convalescence), and 154 from subjects who had two IgG-positive samples obtained 12 months apart (past infection), was tested with 20 toxoplasma-antibody assays and 195 combinations. In general, every assay with high diagnostic sensitivity showed low diagnostic specificity, i.e. no assay performed alone could reliably distinguish acute from past infection. Furthermore, no single assay (or combination) could separate convalescence from the other stages of toxoplasma infection. However, excellent diagnostic performances were reached by sequential use of highly sensitive IgM assays and methods examining IgG avidity or stage specificity. IgA or IgM assays were less suitable for confirmation of toxoplasma-IgM positivity. This study documents the strength of test combinations in assessing the stage of toxoplasma infection.

Strategy for diagnosis of congenital toxoplasmosis: evaluation of methods comparing mothers and newborns and standard methods for postnatal detection of immunoglobulin G, M, and A antibodies.

In a study involving 14 laboratories supported by the European Community Biomed 2 program, we evaluated immunologic methods for the postnatal diagnosis of congenital toxoplasmosis (CT). Among babies born to mothers who seroconverted to positivity for toxoplasmosis during pregnancy, we analyzed 55 babies with CT on the basis of persistent anti-Toxoplasma immunoglobulin G (IgG) at 1 year of life and 50 control babies without anti-Toxoplasma IgG at 1 year of life in the absence of curative treatment with pyrimethamine-sulfonamides. We tested in-house methods such as the enzyme-linked immunofiltration assay (ELIFA) or Immunoblotting (IB) for the detection of IgG or IgM; these methods allowed comparison of the immunologic profiles of the mothers and the infants. We compared ELIFA and IB with a commercial enzyme immunoassay (EIA) or in-house immunosorbent agglutination assay (ISAGA) for the detection of IgM or IgA. The performances of combinations of methods were also assessed. A cumulative sensitivity of 98% during a 1-year follow-up was obtained with the ELIFA plus ISAGA combination. Only one case of CT was missed by the ELIFA plus ISAGA combination, whereas three cases were missed by the IB plus ISAGA combination, even though 48% of patients with CT were treated with pyrimethamine-sulfonamides, which are known to inhibit antibody neosynthesis. A similar performance was obtained with either ELIFA or IB in combination with EIA. The difference in performance between ELIFA plus ISAGA and IB plus ISAGA was not statistically significant (P = 0.31), and we conclude that both combinations of tests can be used for the diagnosis of CT in newborns.

Bicentric evaluation of Access Toxo immunoglobulin M (IgM) and IgG assays and IMx toxo IgM and IgG assays and comparison with Platelia Toxo IgM and IgG assays.

The recent Access immunoanalysis system (Sanofi Diagnostics Pasteur) for the serological diagnosis of toxoplasmosis was compared with the Abbott Toxo IMx EIA system, taking the Platelia Toxo immunoglobulin G (IgG) and Platelia Toxo IgM systems as references and using as confirmation methods an indirect fluorescence assay or a dye test for IgG and an immunosorbent agglutination assay (ISAGA) for IgM. A total of 1,461 serum samples were studied, of which 128 were collected from 42 recently seroconverted patients. Sensitivity and specificity rates of the Access system were 97.7 and 99.5%, respectively, for IgM and 98.6 and 100%, respectively, for IgG. Sensitivity and specificity rates of the Abbott IMx EIA system were 91 and 100%, respectively, for IgM and 92.5 and 100%, respectively, for IgG. The Access Toxo IgG and IgM EIA systems were found to be more sensitive than the Abbott Toxo IgG and IgM IMx EIA systems.

Predictive value of fetal serum beta 2-microglobulin for neonatal renal function.

When fetal urinary-tract malformations (UTM) are discovered, management is based on the prediction of postnatal renal function, currently made by fetal urinary biochemistry and sonography. Serum beta 2-microglobulin has been used postnatally to estimate renal function and does not cross the placenta. We investigated the relation between fetal serum beta 2-microglobulin and renal function by comparing 64 unaffected fetuses and 15 fetuses with UTM. A beta 2-microglobulin above a 5.6 mg/L cut-off gave cross-validated sensitivity of 80.0%, specificity of 98.6%, a positive predictive value of 88.9%, and a negative predictive value of 97.1% for our cohort study.

[Prenatal diagnosis of homozygous pyruvate kinase deficiency]. / Déficit homozygote en pyruvate kinase à révélation anténatale.

Two consecutive cases of severe neonatal anaemia due to severe deficiency in pyruvate kinase were observed in the same sibhood. The first child died one hour after birth and the second required major transfusion support. Pyruvate kinase deficiency is a rare cause of congenital anaemia with recessive autosomic inheritance. Clinically, this deficiency has a very variable expression, and neonatal forms are not always very severe. Several variant molecules in pyruvate kinase deficiency have been described. Recent progress in our understanding of the gene would suggest the possibility of new diagnostic and prognostic approaches.

Prenatal identification of an isochromosome for the short arm of the Y i(Yp), by cytogenetic and molecular analyses.

A case of 45,X/46,X,+mar mosaicism was detected in a male fetus (27 weeks' gestation) referred for karyotype analysis following the observation of a short femur at the ultrasound scan. Analysis of 12 Y-chromosome loci by fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) demonstrated that the marker chromosome is of Y origin and corresponds to an authentic isochromosome for the short arm of the Y chromosome, i(Yp). The breakpoint on this marker is in YQ11.1 close to the centromere. The present report illustrates the importance of FISH and PCR techniques as a complement to cytogenetic methods for accurate identification and characterization of chromosome rearrangements in prenatal diagnosis.

[Value of the study of IgG avidity for the diagnosis of toxoplasmosis]. / Intérêt de l'étude de l'avidité des IgG pour le diagnostic de la toxoplasmose.

The usefulness of IgG avidity analysis for dating acquired toxoplasmosis was documented by a study of 145 serial sera from 39 patients with acute toxoplasmosis and 104 sera from patients with chronic toxoplasmosis. ELISA measurement of IgG avidity involved comparison, for each serum at limit dilution, of optical densities obtained with and without washing with a urea solution to disrupt antigen-antibody bonds. A significant correlation was found between time since onset of toxoplasmosis and IgG avidity. Furthermore, comparison of IgG avidity of sera from patient with chronic infection or with acute infection monitored serologically for less than 20 weeks showed that an avidity index of 0.5 or more was inconsistent with toxoplasmosis of less than 20 weeks duration.

Radiographic, haematological, and biochemical findings in a fetus with Caffey disease.

An early case of prenatal Caffey disease is reported. Ultrasound examination performed at 20 weeks showed major angulations of long bones, but both ultrasound scan and X-rays failed to make the differential diagnosis between Caffey disease and lethal osteogenesis imperfecta. A cordocentesis allowed us to find important biological abnormalities. The pregnancy was terminated after the rapid development of hydrops fetalis. The definitive diagnosis of Caffey disease was obtained by special X-ray and pathological study.

Anti-P30 IgA antibodies as prenatal markers of congenital toxoplasma infection.

This study extends a previous study and confirms that the detection of anti-P30 IgA antibodies is very helpful in the diagnosis of acute acquired or congenital toxoplasmosis. Moreover, we demonstrate that an anti-P30 IgA response can be mounted in the fetuses infected by Toxoplasma gondii during their intra-uterine life as early as week 23 of gestation. A double-sandwich ELISA described in our previous work was used to detect anti-P30 IgA antibodies in 1378 human serum samples collected from 551 patients, including 162 fetuses whose mothers had been infected by T. gondii during pregnancy, 46 congenitally infected and 90 uninfected newborns and 253 women suspected of having been infected during pregnancy, including the mothers of fetuses and newborns previously described. Anti-P30 IgA antibodies were detected in all cases of acute toxoplasmosis but in no case of chronic toxoplasmosis: in the majority of cases, the IgA antibody titre fell below cut-off in 3-9 months. Among the 46 congenitally infected newborns, anti-P30 IgA antibodies were detected in sera of 41 infected newborns (38 at birth, two in the first months of life, one in the seventh month of life), while anti-P30 IgM antibodies were detected in only 30 cases at birth and in one case during the first month of life. Among 162 fetuses, anti-P30 IgA response was observed in five infected fetuses, but was not detected in either 152 uninfected fetuses or in five fetuses considered as infected. The absence or presence of anti-P30 IgA antibodies in the fetus is discussed in relation to the date of maternal infection and collection of the fetal blood. It clearly appears from our study that the combined testing of both IgM and IgA in the fetus and the newborn is essential for a more efficient diagnosis of infection.

[The difficulty of diagnosing Caffey's disease in utero. Apropos of a case simulating lethal osteogenesis imperfecta]. / La difficulté du diagnostic de la maladie de Caffey in utero. A propos d'un cas simulant l'ostéogenèse imparfaite létale.

A very early case of infantile cortical hyperplasia (Caffey disease) is reported. The ultrasound examination performed at 22 weeks gestational age evidenced angulations of the long bones, leading to the diagnosis of lethal osteogenesis imperfecta. Hydrops fetalis developed and the pregnancy was terminated. The roentgenographic study of the fetus and results of pathological studies led to the correct diagnosis of Caffey disease. The difficulty of the diagnosis of these early forms of infantile cortical hyperostosis should be pointed out.

[Inconvenience of planned prophylaxis of transfusion-induced alloimmunization to red cells in chronic renal insufficiency]. / Inopportunité de la prophylaxie élaborée de l'allo-immunisation transfusionnelle contre les globules rouges dans l'insuffisance rénale chronique.

Records from 506 hemodialysis multitransfused patients were reviewed to evaluate the incidence of transfusion induced red cell allo-immunization. Out of 405 patients having received a total of 6 608 red cell transfusions compatible for A, B and D antigens, only 7 patients (1.72%) developed allo-antibodies which may be attributed to such transfusions. Elaborate red cell phenotyping in un-immunized recipients and selection of blood units compatible for other antigens than A, B and D in an effort to prevent red cell allo-immunization to other blood group antigens in such potentially multitransfused patients does not accordingly appear to be justified and cost-effective.

[Limited indications for phenotyped blood in the prevention of transfusion-induced anti-red blood cell alloimmunization in chronic kidney failure]. / Limite des indications du sang phénotypé pour la prévention de l'alloimmunisation transfusionnelle anti-globules rouges dans l'insuffisance rénale chronique.

Records from 506 multitransfused patients on a program of hemodialysis were reviewed to evaluate the incidence of transfusion-induced red cell alloimmunization. Out of 405 patients having received a total of 6608 red cell transfusions compatible for A, B and D antigens, only 7 patients (1.72%) developed allo-antibodies which may be attributed to such transfusions. Elaborate red cell phenotyping in non-immunized patients and selection of blood units compatible for other antigens than D does not accordingly appear to be justified and cost-effective.