IgG and IgM western blot assay for diagnosis of congenital toxoplasmosis

The aim of this study was to evaluate the utility of western blot (WB) analysis as a diagnostic tool for congenital toxoplasmosis in 215 newborn infants. The children were submitted to clinical examinations to assess macular, neurological and hearing signals. The WB results obtained were compared to the persistence of IgG antibodies at the end of 12 months, which is regarded as the "gold standard" diagnosis of congenital toxoplasmosis. Association between the WB results and the clinical signs presented by the infants was also assessed. Of the 215 children, 177 had a confirmed congenital toxoplasmosis diagnosis and 38 were uninfected. IgG-WB showed a sensitivity of 73.5 percent and a specificity of 97.4 percent. IgM-WB showed a sensitivity of 54.8 percent and a specificity of 94.7 percent. The IgG-WB and IgM-WB combination increased the sensitivity to 86.5 percent. The IgM-WB-positive children had a 1.4-fold greater risk of presenting active macular lesions than did those that were IgM-WB-negative. This study showed that the WB assay is a useful tool to confirm a diagnosis of congenital toxoplasmosis and that the IgM-WB-positive results can indicate active macular lesions in newborn infants.

Toxoplasmose congênita em filho de mãe cronicamente infectada com reativação de retinocoroidite na gestação / Congenital toxoplasmosis from a chronically infected woman with reactivation of retinochoroiditis during pregnancy an underestimated event?

Objetivo: Apresentar um caso raro de toxoplasmose congênita de uma mãe imunocompetente com infecção crônica que teve reativação da doença ocular durante a gestação. Descrição: O recém-nascido estava assintomático no nascimento e foi identificado através de triagem neonatal (IgM anti-Toxoplasma gondii em sangue seco) entre outros 190 bebês com toxoplasmose congênita durante um período de 7 meses. Sua mãe tinha tido um episódio não tratado de reativação de retinocoroidite toxoplásmica durante a gestação, com títulos de IgG estáveis e resultados negativos para IgM. Os resultados de IgM e IgG no soro do recém-nascido e o teste de immunoblotting para IgG foram positivos, e detectou-se lesões retinocoroideanas ativas na periferia da retina. O recém-nascido foi tratado com sulfadiazina, pirimetamina e ácido folínico. Aos 14 meses de vida, a criança permanecia assintomática, com regressão das lesões retinocoroideanas e persistência de IgG. Comentários: É possível que a triagem neonatal sistemática em áreas com alta prevalência de infecção possa identificar esses casos.

Objectives: To report a rare case of congenital toxoplasmosis from an immunocompetent mother with chronic infection who had reactivation of ocular disease during pregnancy. Descriptions:The newborn was asymptomatic at birth and identified by neonatal screening (IgM anti-Toxoplasma gondii in dried blood) among other 190 infants with congenital toxoplasmosis during a 7-month period. His mother had had a non-treated episode of reactivation of toxoplasmic retinochoroiditis during pregnancy, with stable IgG titers and negative IgM results. Results of IgM and IgG in the newborn’s serum, as well as IgG immunoblotting were positive and active retinochoroidal lesions were detected in his peripheral retina. The neonate was treated with sulfadiazine, pyrimethamine and folinic acid. At 14 months of life, the child remained asymptomatic, with regression of retinochoroidal lesions and persistence of IgG. Comments: It is possible that systematic neonatal screening in areas with high prevalence of infection may identify these cases.