Evaluation of diagnostic tests for Wuchereria bancrofti infection in Brazilian schoolchildren

Introduction Since the launch of the Global Programme to Eliminate Lymphatic Filariasis, more than 70% of the endemic countries have implemented mass drug administration (MDA) to interrupt disease transmission. The monitoring of filarial infection in sentinel populations, particularly schoolchildren, is recommended to assess the impact of MDA. A key issue is choosing the appropriate tools for these initial assessments (to define the best intervention) and for monitoring transmission. Methods This study compared the pre-MDA performance of five diagnostic methods, namely, thick film test, Knott's technique, filtration, Og4C3-ELISA, and the AD12-ICT card test, in schoolchildren from Brazil. Venous and capillary blood samples were collected between 11 pm and 1 am. The microfilarial loads were analyzed with a negative binomial regression, and the prevalence and associated 95% confidence intervals were estimated for all methods. The accuracies of the AD12-ICT card and Og4C3-ELISA tests were assessed against the combination of parasitological test results. Results A total of 805 schoolchildren were examined. The overall and stratified prevalence by age group and gender detected by Og4C3-ELISA and AD12-ICT were markedly higher than the prevalence estimated by the parasitological methods. The sensitivity of the AD12-ICT card and Og4C3-ELISA tests was approximately 100%, and the positive likelihood ratios were above 6. The specificity of the Og4C3-ELISA was higher than that of the AD12-ICT at different prevalence levels. Conclusions The ICT card test should be the recommended tool for monitoring school-age populations living in areas with ongoing or completed MDA. .

Avaliação da especificidade dos primers RV1 e RV2 para o diagnóstico molecular da leishimaniose visceral / Evaluation of the specificity of the primers RV1 and RV2 for the molecular diagnosis of visceral leishimaniose

A Leishmaniose Visceral (LV) é uma endemia de grande expansão geográfica e, na maioria das áreas endêmicas, co-existe com outras doenças. No Brasil há descrição, em vários municípios, de co-endemias tais como esquistossomose, tuberculose, doença de chagas e leishmaniose tegumentar americana, e estas apresentam manifestações clínicas semelhantes à LV, o que pode interferir na especificidade dos métodos diagnósticos convencionais. O minicírculo do kDNA é o alvo mais estudado e aplicado nas pesquisas da leishmaniose humana. Dentre os primers que tem o kDNA como alvo estão o RV1 e RV2, que já foram aplicados com sucesso em diversas amostras biológicas. Este trabalho teve como objetivo estudar a especificidade dos primers RV1 e RV2, através da técnica de PCR, utilizando DNA de diferentes organismos. Para isto, utilizou-se a ferramenta Primer-BLAST (NCBI), para observar, teoricamente, quais os organismos que possuem regiões para o anelamento dos primers; e, em laboratório, foram testados DNA genômico purificado de diversos organismos. A sensibilidade dos primers foi testada através de uma curva de diluição seriada utilizando o DNA genômico de Leishmania (Leishmania) chagasi para dois sistemas de volumes diferentes. O Sistema de PCR 2, com 50 ?L, apresentou uma sensibilidade de 0,1fg, enquanto que o Sistema de PCR 1, com 25 ?L, alcançou apenas 1 pg. Testando os primers dos sistemas de forma teórica (Primer-BLAST), estes mostraram-se específicos para Leishmania (Leishmania) major, Leishmania (Leishmania) donovani e Leishmania. (Leishmania) infantum. Porém ao testar, em laboratório, o DNA dos organismos com o sistema de PCR 2, observou-se inespecificidade dos primers, que se anelaram frente ao DNA de Schistosoma mansoni e Trypanosoma cruzi, para as mesmas condições de ciclagem. Os resultados encontrados demonstram que os primers RV1 e RV2 não devem ser utilizados em regiões onde estes parasitos estão presentes, pois podem levar a resultados falso-positivos.

The Visceral Leishmaniasis (VL) is endemic to a large geographic spread and, in most endemic areas, co-exist with other diseases. In Brazil there are descriptions, in various municipalities, of co-endemic diseases such as schistosomiasis, tuberculosis, chagas disease and american tegumentary leishmaniasis, and those with clinical symptoms similar to VL, which can interfere with the specificity of conventional diagnostic methods.The minicircle kDNA is the target most studied and applied in research of human leishmaniasis. Among the primers that target the kDNA, are RV1 and RV2, which has already been successfully applied in various biological samples. This work aimed to study the specificity of the primers RV1 and RV2, by PCR, using DNA from different organisms. For this, we used the Primer-BLAST tool (NCBI), to observe, theoretically, which organisms have regions for annealing ofprimers, and in the laboratory were tested purified genomic DNA of various organisms. The sensitivity of primers was tested by a serial dilution curve using genomic DNA from Leishmania (Leishmania) chagasi for two systems with different volumes. The PCR System2, with 50 ìL, showed a sensitivity of 0.1 fg, whereas the PCR System 1, with 25 ìL, reached only 1 pg. Testing primers in a theoretical way (Primer-BLAST), they showed specificity forLeishmania (Leishmania) major, Leishmania (Leishmania) donovani and Leishmania (Leishmania) infantum. But when testing, in laboratory, the DNA of the organisms using the PCR system 2, was observed inspecificity of the primers, which showed amplification against the DNA of Schistosoma mansoni and Trypanosoma cruzi, using the same cycling conditions. The results show that the primers RV1 and RV2 must not be used in regions where theseparasites are present, because they may lead to false positive results.