Abstract
The purpose of the present study is to standardize and evaluate the use of the immunoglobulin G (IgG) antibody avidity test on blood samples from newborns collected on filter paper to perform the heel test aiming at its implementation in ongoing programs. Blood samples from newborns were collected on filter paper simultaneously with the heel prick test. All samples were subjected to immunoglobulin M IgM and IgG enzyme-linked immunosorbent assays (ELISA). Peripheral blood was collected again in the traditional way and on filter paper from newborns with high IgG levels (33). Three types of techniques were performed, the standard for measuring IgG in serum, adapted for filter paper and the technique of IgG avidity in serum and on filter paper. The results of the avidity test were classified according to the Rahbari protocol. Among the 177 samples, 17 were collected in duplicate from the same child, 1 of peripheral blood and 1 on filter paper. In this analysis, 1 (5.88%) of the 17 samples collected in duplicate also exhibited low IgG avidity, suggesting congenital infection. In addition, the results obtained from serum and filter paper were in agreement, that is, 16 (94.12%) samples presented high avidity, with 100% agreement between the results obtained from serum and from filter paper. The results of the present study indicate that the avidity test may be another valuable method for the diagnosis of congenital toxoplasmosis in newborns.
Highlights
Congenital toxoplasmosis is an infectious disease caused by the transplacental transfer of Toxoplasma gondii tachyzoites from the primary infection of the mother, by reinfection, or by resurgence of a previous infection, and is relevant because of the damage inflicted on the developing fetus.[1]Toxoplasmosis is one of the most harmful diseases for the fetus, when the mother becomes infected in the 1st 2 trimesters of pregnancy.[2]
The results of the present study indicate that the avidity test may be another valuable method for the diagnosis of congenital toxoplasmosis in newborns
In the routine laboratory tests offered by the Brazilian Unified Health System (SUS, in the Portuguese acronym), toxoplasmosis is diagnosed by means of serological tests based on the detection of specific antibodies of the classes of immunoglobulin M (IgM) and immunoglobulin G (IgG), mainly by means of the enzyme-linked immunosorbent assay (ELISA) method.[10]
Summary
Congenital toxoplasmosis is an infectious disease caused by the transplacental transfer of Toxoplasma gondii tachyzoites from the primary infection of the mother, by reinfection, or by resurgence of a previous infection, and is relevant because of the damage inflicted on the developing fetus.[1]Toxoplasmosis is one of the most harmful diseases for the fetus, when the mother becomes infected in the 1st 2 trimesters of pregnancy.[2]. Congenital toxoplasmosis is an infectious disease caused by the transplacental transfer of Toxoplasma gondii tachyzoites from the primary infection of the mother, by reinfection, or by resurgence of a previous infection, and is relevant because of the damage inflicted on the developing fetus.[1]. Pregnant women often have access to exams only in the last month of pregnancy, when prenatal tests are performed in programs that use filter paper for serological screening. This situation is one of the main factors that limit the control and the prevention of infection, of confirmation of risk, and of congenital transmission.[11]
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