[Evaluation of prevention strategies for congenital toxoplasmosis: a critical review of medico-economic studies]. / Evaluation de stratégies de prévention de la toxoplasmose congénitale: revue critique des études médico-économiques.

BACKGROUND: Congenital toxoplasmosis (CT) may lead to serious neurological or sensory consequences. A serological screening of women at risk of acquiring toxoplasmosis became mandatory in France, first during the visit before wedding (1978), then during the visit for pregnancy declaration (1985) and at last with a monthly follow-up during pregnancy since 1992. The efficacy and the profitability of the program was never assessed, in spite of the modification of the epidemiological context. However medico-economical studies were conducted in countries in which no prevention program for CT was available to determine the interest of an antenatal screening similar to the French one or of other prevention strategies. METHODS: Eight studies comparing at least two strategies were selected. Methodologies used in those studies were analyzed by two independent readers with the help of a standardized scale. A score was calculated for each study. RESULTS: Each study analyzed suffered from methodological limitations, in particular concerning the estimation of antenatal treatment efficacy, which could lead to invalidate their conclusion. The most reliable studies in regard to methodological guidelines, that is with the higher score, concluded that antenatal screening was not contributive. However, they could not be transposed directly in the present French situation, because of the difference of the epidemiological and economical context. CONCLUSIONS: Given the difficulty to obtain a clear conclusion, it seems necessary to perform a rigorous decision analysis to identify the more effective and acceptable program in terms of human and financial costs for preventing congenital toxoplasmosis.

[Decision analysis of congenital toxoplasmosis in the absence of exact knowledge of the treatment benefits and secondary effects]. / Analyse de décision dans la toxoplasmose congénitale en l'absence de connaissance exacte des bénéfices et effets secondaires de la thérapeutique.

Decision analysis seemed the appropriate method to bring out the interest of toxoplasmosis serology in children born from mothers who seroconverted during pregnancy. In particular it provides the possibility to choose between IgA serology, recently introduced in hospital practice, and IgM serology that is the reference test. We study a series of 96 children suspected of having congenital toxoplasmosis who were followed up until the age of one. A decision analysis is thereafter conducted by synthesizing data about clinical efficacy with the RBNCN ratio that is the net benefit of treating an affected person divided by the net cost of treating an unaffected person; these costs and benefits are clinical. The effectiveness of the treatment (sulphonamides in most cases) was not quantified. Therefore, we used the fact that the RBNCN ratio is equal to the number of healthy children likely to be treated unnecessarily in order not to leave untreated a contaminated child. Although data available in the literature and data from our study still remain insufficient to draw a final conclusion, IgA antibodies are significantly more sensitive than IgM antibodies (p < 0.01). Conversely, IgA antibodies are significantly less specific than IgM antibodies (p < 0.001). The sensitivity analysis shows that the IgA test is preferred to the IgM test if the mother is contaminated during the third trimester. On the other hand, for low prevalences, as observed in the first trimester, the IgM serology is more useful.