Infectious etiology and indicators of malabsorption or intestinal injury in childhood diarrhea. / Etiología infecciosa e indicadores de malabsorción o daño intestinal en diarrea infantil

INTRODUCTION: The multifactorial etiology of gastroenteritis emphasizes the need for different laboratory methods to identify or exclude infectious agents and evaluate the severity of diarrheal disease. OBJECTIVE: To diagnose the infectious etiology in diarrheic children and to evaluate some fecal markers associated with intestinal integrity. MATERIALS AND METHODS: The study group comprised 45 children with diarrheal disease, tested for enteropathogens and malabsorption markers, and 76 children whose feces were used for fat evaluation by the traditional and acid steatocrit tests. RESULTS: We observed acute diarrhea in 80% of the children and persistent diarrhea in 20%. Of the diarrheic individuals analyzed, 40% were positive for enteropathogens, with rotavirus (13.3%) and Giardia duodenalis (11.1%) the most frequently diagnosed. Among the infected patients, occult blood was more evident in those carrying pathogenic bacteria (40%) and enteroviruses (40%), while steatorrhea was observed in infections by the protozoa G. duodenalis (35.7%). Children with diarrhea excreted significantly more lipids in feces than non-diarrheic children, as determined by the traditional (p<0.0003) and acid steatocrit (p<0.0001) methods. Moreover, the acid steatocrit method detected 16.7% more fecal fat than the traditional method. CONCLUSIONS: Childhood diarrhea can lead to increasingly severe nutrient deficiencies. Steatorrhea is the hallmark of malabsorption, and a stool test, such as the acid steatocrit, can be routinely used as a laboratory tool for the semi-quantitative evaluation of fat malabsorption in diarrheic children.

Introducción. La etiología multifactorial de la gastroenteritis enfatiza la necesidad de usar diferentes métodos de laboratorio para identificar o excluir agentes infecciosos y evaluar la gravedad de la enfermedad diarreica. Objetivo. Diagnosticar la etiología infecciosa de la diarrea en niños y evaluar algunos marcadores fecales asociados con la integridad intestinal. Materiales y métodos. Se estudiaron 45 niños con enfermedad diarreica, en los cuales se evaluaron la presencia de enteropatógenos y los marcadores de malabsorción. Se analizaron las muestras fecales de 76 niños, mediante las pruebas de esteatocrito tradicional y esteatocrito ácido, para la cuantificación de la grasa. Resultados. Se observó diarrea aguda en el 80 % de los niños y diarrea persistente en el 20 %. De los individuos con diarrea, el 40 % fue positivo para enteropatógenos; los más diagnosticados fueron rotavirus (13,3 %) y Giardia duodenalis (11,1 %). Entre los pacientes infectados, la sangre oculta fue más evidente en aquellos portadores de bacterias patógenas (40 %) o enterovirus (40%), mientras que la esteatorrea se observó en infecciones por el protozoo G. duodenalis (35,7 %). Los niños con diarrea excretaron significativamente más lípidos en las heces que aquellos sin diarrea, según lo determinado por los métodos de esteatocrito tradicional (p<0,0003) y esteatocrito ácido (p<0,0001). Conclusiones. La diarrea infantil puede provocar deficiencias graves de nutrientes. La esteatorrea es distintiva de la malabsorción intestinal y puede detectarse mediante la estimación del esteatocrito ácido. Esta prueba podría utilizarse de forma rutinaria como una herramienta de laboratorio para la evaluación semicuantitativa de la malabsorción de grasas en niños con diarrea.

Detection of IgG Anti-Giardia duodenalis Antibodies in Sera by Indirect Immunofluorescence and Western Blotting Assays.

INTRODUCTION: Serological assays are alternative laboratory tools for the diagnosis of parasitic infections. The aim of this work was to evaluate the performance of the indirect fluorescent antibody test (IFAT) and Western blotting (WB) for the detection of IgG anti-Giardia antibodies in human sera. METHODOLOGY: Sera from individuals infected with Giardia duodenalis, other parasites or non-parasitized were selected for serological assays. Ninety-seven sera were tested by IFAT at 1:20 and 1:40 dilutions and of these, 40 samples were also analyzed by WB. RESULTS: The sensitivity and specificity of the IFAT was 97% and 46.9% at 1:20 sera dilution, and 39.4% and 59.4% at 1:40 sera dilution. The low molecular weight polypeptides fractions of 25 kDa, 27-31 kDa and 45-55 kDa were the most frequently identified by the sera of individuals infected with G. duodenalis, along with low cross-reactivity, presenting an individual sensitivity of 42.8%, 50.0% and 57.1%, and specificity of 83.3%, 83.3% and 91.7%, respectively. The highest overall sensitivity of WB (85.7%) was based on the immunoreactivity of sera with at least one of those proteins. The concordance between the detection of G. duodenalis in feces by microscopy and the WB results was considered substantial (Kappa = 0.61). CONCLUSION: Constant exposure to Giardia infection throughout a lifetime can maintain high levels of specific antibodies in serum, even without active infection. Moreover, proteins found in intestinal amoebas may hinder the serological diagnosis of giardiasis in endemic areas due to cross-reactivity, which can be partially solved using Giardia low molecular weight proteins.

Specific IgG and IgA Antibody Reactivities in Sera of Children by Enzyme-Linked Immunoassay and Comparison With Giardia duodenalis Diagnosis in Feces.

BACKGROUND: Giardia duodenalis is conventionally diagnosed in fecal samples using parasitological methods. However, sensitivity is poor when only a single sample is analyzed, due to intermittent excretion of cysts in feces. Alternatively, the serum antibodies to G. duodenalis can be used for parasite diagnosis and epidemiological studies to determine previous exposure. We compared the rate of G. duodenalis infection between serum anti-Giardia IgG and IgA antibodies and fecal examination in Brazilian children. METHODS: Fecal and serum samples were tested from 287 children at a clinical laboratory and from 187 children at daycare centers. Fecal samples were processed using conventional parasitological methods and coproantigen detection for Giardia diagnosis. Serum samples were tested using an in-house ELISA for detection of anti-Giardia IgG and IgA. RESULTS: G. duodenalis was found in 8.2% (N=39) of the 474 children analyzed. The sensitivity and specificity of ELISA were 80.0% and 90.0% for IgG and 80.0% and 83.3% for IgA, respectively. The total positivity rate of anti-Giardia IgG and IgA in the sera was 13.9% (N=66) and 23.6% (N=112). The agreement between the positivity of specific antibodies and the detection of G. duodenalis in feces was moderate for ELISA-IgG, kappa index (95% CI)=0.543 (0.422-0.664), and mild for ELISA-IgA, kappa index (95% CI)=0.283 (0.162-0.404). Among the children infected with other enteroparasites, 11.6% (N=10) and 24.4% (N=21) showed reactivity to anti-Giardia IgG and to IgA, respectively. This cross-reactivity was more frequent in samples from children infected with Endolimax nana and Entamoeba coli. CONCLUSIONS: The higher frequency of specific antibody reactivity compared with G. duodenalis diagnosis in feces could reflect continuous exposure of children to G. duodenalis infection, resulting in long-lasting immunological memory and/or cross-reactivity with other intestinal amoebas.