Valor diagnostico de la inmunofluorescencia indirecta con anti-IgM para Enfermedad de Chagas, en adultos y recién nacidos

Abstract

Diagnostic value of the IgM Immunofluorescence test for chagas' disease in infants andadults.The IFAT-IgM with Trypanosoma cruzi antigen was applied in a double blind study of 242 serum samples previously examined by the IFAT-IgG for Chagas' disease. The sensitivity of the test was enhanced by prolonged incubation at 4°C. The specificity of the IgM reaction in normal sera, was checked repeting the test in alliquots, absorbed with IgG. The results were tabulated according to the origin of the samples and the presence, or absence, of IgG antibodies for Chagas' disease. 84 of die samples belonged to infants and 158 to adults,131 had IgG antibodies against T. cruzi and the remaining 111 served as negative controls in both groups.In was demonstrated that a high proportion of positive IgM-results obtained in normal sera, of infants (15,5%) and adults (28,5%), were due to otfier factors: Elimination of nonspecific IgM antibodies, by absorbtion, reduced the reactions of IgM, at liters of 1/10 and 1/20, to three samples in the infant's group. However, in the sera of adults, positive IgM results remained after absorbtion, at titers up to 1/20, in the infected individuals as well as in controls. Only one serum gaveatiterof 1/40, suggesting specificity.The three samples of the infant's group, in which IgM antibodies to T. cruzi were demonstrated, belonged to a child with Chagas' disease demonstrated by xeno-diagnosis. The specimen oi the adult in which a positive IFAT-IgM-Chagas was obtained at a titer of 1/40, corresponded to a women with recently acquired infection, as jugdedbyaseroconversion(from(-)to( + ) 1/40) in the IFAT-IgG for Chagas' disease.The results indicate that the test yields specific results, if it is applied in sera previously absorbed with IgG and confirm that low titers are of diagnostic value in sera of infants. However, in sera of adults, only titers from 1/40 onward are considered to be specific for Chagas's disease.El empleo de la reacci6n de inmunofluorescencia Indirecta (RIFI), ha permitido ampliar el estudio serologico en diferentes enfermedades inlecciosas. Dicha tecnica, de ejecuci6n relativamente simple y rapida, ofrece la doble ventaja de ser aplicable tanto en la pesquisa de diferentes agentes infecciosos, lo que depende del microorganismo que se emplee como antigeno, conio en la demostraci6n de diferentes tipos de anticuerpos, de acuerdo con la antigammaglobulina que se utilice como reactivo. La RIFI practicada con antigammaglobulina de tipo IgG y antigeno de Trypanosoma cruzi {RIFI-IgG-Chagas), ha tenido gran aceptacion en el estudio de la enfermedad de Chagas, recomendandose su empleo para el diagnostico del caso individual y para los estudios epidemiol6gicos. longada, incluso indefinida, diagnostica la infecci6n y permite establecer su prevalencia. Sin embargo, esta informaci6n puede ampliarse, si en los sueros positives se practica ademas, una RIFIIgM. Los anticuerpos de este tipo, debido a su aparicion precoz y duracion limitada, caracterizan la fase aguda de la infecci6n; de modo que l...

Chagas disease: an overview of diagnosis

“…44 The detection of antibodies (IgG) against T. cruzi and the parasite's presence for prolonged periods, stimulates the prevalence of this disease. 66,67 In addition to the use of IgG antibodies, is possible to use IgM antibodies. These types of immunoglobulins are the first to appear during an adaptive response and are of limited duration.…”

“…Because of the latter, the use of specific IgM antibodies against T. cruzi indicates an acute phase of Chagas disease, even in urine samples (80-kilodalton Trypanosoma cruzi antigen). [67][68][69] In addition to the use of immunofluorescence and IgM as an early marker of infection, its main application is in the detection of congenital infections. The pentameric nature of IgM prevents it from traversing the intact placenta.…”

“…70 In addition, the fetus is capable of generating IgM antibodies by itself in response to foreign agents. 67 Therefore, the detection of IgM antibodies against T. cruzi detected in the blood of newborns is an indicator of a transplacental infection. 67,68 Nevertheless, false positives have been observed due contamination of IgM antibodies from the mother to the fetus, coming from damage to the integrity of the placenta and through maternal blood during childbirth.…”

“…67 Therefore, the detection of IgM antibodies against T. cruzi detected in the blood of newborns is an indicator of a transplacental infection. 67,68 Nevertheless, false positives have been observed due contamination of IgM antibodies from the mother to the fetus, coming from damage to the integrity of the placenta and through maternal blood during childbirth. 67,71,72 Despite the diagnostic advances and the fact that serological methods are in many cases sensitive and specific, it's necessary to perform complementary tests (xenodiagnostic, PCR, electrocardiogram, echocardiogram, etc.)…”

El Estudio de las Infecciones Congénitas por Toxoplasma Gondii y Trypanosoma Cruzi

“…La RIFI-IgM constituye un aporte util al diagnostico de la infeccion congenita cuando resulta positiva; sin embargo, una RIFI-IgM negativa no descarta el diagnostico 23 . 3a.…”