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Congenital toxoplasmosis: systematic review of evidence of efficacy of treatment in pregnancy
- Elio Castagnola, Giuliana Carrega (16 June 1999)
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Elio Castagnola (1) G.Gaslini Children's Hospital, Genoa (2) Ospedale S.Corona, Pietra Ligure - ITALY, Giuliana Carrega
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Sir, we red with great interest the paper from Wallon and Co-workers (1) about efficacy of treatment of toxoplasmosis during pregnancy. However we have some question about the conclusions. First it is our opinion that selected studies are not adequate to give an answer the study-question for different reasons: 1) the papers’ selection process decision does not take into any account if the administered treatment was appropriate in dosage and duration. These are well known important variables for determine the result of anti-infective therapies. Women becoming infected after inappropriate therapy could not be considered a “failure” of the screening system, but a failure of the medical practice! 2) the date of maternal infection was taken into account in only one of the selected papers (2).Since time of infection is an important varible in determining the risk of congenital toxoplasmosis (3), we lack of another important information to evaluate efficacy of treatment; 3) many of the selected studies do not seem to be numerically appropriate to give an answer regarding the primary question: 7 of them involved few patients (in 2 patients were “very” few) and 2 only have a number of cases and controls with more than 100 patients in each arm. If we consider the only 2 studies (4,5) with large (probaby adequate) patient samples (6) (with a quality score of 3 and 4 according with Authors’ definitions) the infection rate is 24% (229/952) for women who received treatment and 40% (111/279) for women who did not receive any treatment In the wake of these observations, the selected studies do not support any comment about efficacy of anti-Toxoplasma treatment during pregnancy and, by consequence, do not allow any conclusion about the utility of screening for toxoplasmosis during pregnancy. Treatment of toxoplasmosis during pregnancy is administered in the attempt to reduce both incidence and severity of congenital disease. The treatment of women with a recently aquired infection (detected by a screening program) could prevent spreading of Toxoplasma to the fetus, since there is a significant lag period between maternal infection and infection of the fetus (3). The cost saved by reducing the incidence of early or late disease (remember chorioretinitis in the adults!) (3) due to congenital toxoplasmosis justify the use of a screening test. Bibliography 1. Martine Wallon, Christiane Liou, Paul Garner, François Peyron Congenital toxoplasmosis: systematic review of evidence of efficacy of treatment in pregnancy BMJ 1999;318:1511–4 2. Excler JL, Piens MA, Maisonneuve H, Pujol E, Garin JP. Dépistage de la toxoplasmose acquise chez la femme enceinte et de la toxoplasmose congénitale chez le nouveau.né. Lyon Med 1985;253:33-8. 3. Remington JS, MCLeod R, Desmonts G. Toxoplasmosis. In: Remington JS, Klein JO (Eds): Infectious diseases of the fetus and newborn infant. WB Saunders CO: London 1995; pp:140-267. 4. Wallon M, Peyron F, Lebech M, Petersen E, Gilbert R, Dunn D. Prenatal treatment and the risk of congenital toxoplasmosis: preliminary findings from two cohort studies [abstract No 94.] European Society for Research in Pediatrics annual meeting, Szedeg, Hungary 1997. Pediatr Res 1997;42:400. 5. Desmonts G, Couvreur J. Toxoplasmose congénitale. Ann de Pediatr (Paris) 1984;31:805-9. 6. Bailar JC III, Mosteller F, Eds: Medical uses of statistics NEJM Books: Boston MA 1992; pp: 5-449 |
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