Diagnosis of congenital toxoplasmosis at birth: what is the value of testing for IgM and IgA?

UNLABELLED: Recommendations vary on the best combination of tests to use for the diagnosis of subclinical congenital toxoplasmosis at birth. The diagnostic accuracy of IgM and IgA tests was assessed in the context of routine clinical practice on 233 newborns with congenital toxoplasmosis and 661 healthy controls. IgM/IgA sensibility and specificity were compared in cord and postnatal samples. Both tests were considerably more specific in neonatal blood (IgM: 98%; IgA: 100%) than in cordblood (IgM: 85%; IgA: 88%). Sensitivity for IgM and IgA was not significantly different in neonatal blood (61% and 60%, respectively) and cord blood (67% and 54%, respectively). Combining IgM and IgA increased the overall sensitivity to 73% without any significant loss in specificity (98%). The influence of the date of maternal infection on the sensitivity and negative predictive value was also clearly demonstrated. CONCLUSION: Because of their relatively low cost compared to more sophisticated methods, IgM and IgA tests should remain the main method for the routine diagnosis of congenital toxoplasmosis although follow up is essential to identify the Ca. 25% of infected children who are missed at birth on the basis of these tests.

[Importance of antiproteases in the treatment of microsporidia and/or cryptosporidia infections in HIV-seropositive patients]. / Intérêt des antiprotéases dans le traitement des infections à microsporidies et/ou cryptosporidies chez des patients VIH-séropositifs.

Diarrhea due to infection with Microsporidium (M) or Cryptosporidium (C) raises significant therapeutic challenges in HIV-infected patients. The usefulness of protease inhibitor therapy was evaluated in 20 HIV-positive patients with positive tests for M and/or C. There were 17 men and three women with a mean age of 42.5 years (range, 26-64 years). Two patients had category B disease and 18 category C disease according to the 1993 CDC classification scheme (CD4 count before therapy, 72/mm3; mean viral burden, 4.6 log). Seventeen patients had chronic diarrhea (due to M in 12 cases and to C in five), and the remaining three patients were asymptomatic M carriers. Clinical symptoms resolved after addition to the antiretroviral regimen of indinavir (n = 17) or saquinavir (n = 3). Mean weight gain was 10.5 kg. Karnofsky's index improved. Twelve patients, including one of the three who were asymptomatic at baseline, had negative follow-up stool cultures. The mean CD4 count increase was 125/mm3, and the mean viral burden decrease was 1.285 log. These data suggest that protease inhibitors may be capable of eradicating M and/or C infection refractory to other treatments. The reason for this effect may involve partial restoration of immune function due to inhibition of HIV replication.

A second European collaborative study on polymerase chain reaction for Toxoplasma gondii, involving 15 teams.

In order to investigate the accuracy and practicability of the polymerase chain reaction (PCR) in the antenatal diagnosis of congenital toxoplasmosis, a collaborative study involving 15 European laboratories was performed under the auspices of the Biomed 2 Programme of the European Community. Each team received 12 aliquots (four negative, eight positive) of 'artificial samples' made of amniotic fluid spiked with tachyzoites of the RH strain of Toxoplasma gondii. Each team performed its own PCR protocol (all were different). Nine of the 15 laboratories were able to detect a single parasite, but two of the 15 found all samples negative. Four of the 15 laboratories found one or more control samples to be falsely positive. This study highlights the lack of homogeneity between PCR protocols and performance and underlines the need for an external quality assurance scheme which could provide 'reference' samples that could be used by any laboratory wanting to establish and maintain an accurate diagnostic test based on PCR.

Value of cerebrospinal fluid cytochemical examination for the diagnosis of congenital toxoplasmosis at birth in France.

BACKGROUND: Because of routine screening and treatment of pregnant women for Toxoplasma infection in France, most neonates born to mothers who seroconverted during pregnancy are either not infected or asymptomatic. Early diagnosis relies mainly on radiologic, ophthalmologic and biologic tests. Cerebrospinal fluid (CSF) cytochemical evaluation is one of several tests performed in parallel to increase the overall sensitivity of the diagnostic evaluation. Our goal was to assess the value of cytochemical examination and to confirm whether using a portion of available CSF for this analysis is legitimate. METHODS: The individual performance of each of the two cytochemical tests and their combined value when used in parallel were assessed. These findings were then compared with the anti-Toxoplasma IgM and IgA serum titers and the clinical, ophthalmologic and radiologic findings at birth. RESULTS: CSF cytochemical analysis was possible in only 52% of the 233 children in the study. Our results in 112 children indicated poor sensitivity estimates. There was no significant change in the posttest probability of infection compared with the pretest estimation of risk in cases of a negative finding. After a mean follow-up of 80 months there was no evidence that CSF cytochemistry helped predict the risk of sequelae. CONCLUSION: In our setting cytochemical examination did not significantly contribute to the diagnosis of congenital infection at birth. Because of the limited quantity of CSF available, we suggest the use of other methods with higher yield.

Identification of Encephalitozoon intestinalis in travelers with chronic diarrhea by specific PCR amplification.

With the use of Weber's modified trichrome and Uvitex 2B techniques, spores of microsporidia were detected in the stools of four travelers presenting clinically with chronic diarrhea. The general health of these patients was not impaired, and human immunodeficiency virus screening was negative. Immune evaluation, including the study of lymphocytic subpopulations, assay of serum immunoglobulins, and an intradermal multitest, showed normal results. Molecular identification of microsporidian species was based on the PCR amplification of a small-subunit rRNA sequence followed by HinfI endonuclease restriction. Encephalitozoon intestinalis microsporidiosis was thus shown in two of the four patients examined. In two patients, therapy based on albendazole made stools devoid of microsporidian spores without influence on the intestinal disorders. The pathogenic role of E. intestinalis in immunocompetent individuals remains to be demonstrated.

[HBV-DNA assay by hybridization in solution. Value of low levels measured with the Abbott-Genostics device]. / Dosage de l'ADN du VHB par hybridation en milieu liquide. Valeur des taux faibles mesurés avec la trousse Abbott-Genostics.

Quantitation of HBV-DNA is the most precise test for measuring viral replication. A commercial liquid phase hybridation test (Abbott) is now commonly used for diagnosis and monitoring of chronic hepatitis B. Interpretation of weak positive results obtained with this test are often difficult. Fifty-four sera with a concentration lower than 12 pg/ml with the Abbott HBV-DNA assay were tested with another commercial hybridation assay (Digene-Murex) and with an in-house PCR test. PCR is positive in 24 sera among the 35 HBs antigen positive sera, but is always negative in HBs Antigene negative sera. All the HBe Antigen positive sera were positive with the PCR test. A positive result was obtained with the Digene test in only 14 sera, 13 of them were confirmed by PCR. Ten sera among the remaining 11 PCR positive sera had a low HBV-DNA concentration but under the Digene cut-off level (10 pg/ml). The sensitivity could be greatly enforced with a lower cut-off level without any lack of specificity. The PCR test remains very helpful for sera with low concentration of HBV-DNA.