Desenvolvimento de um ensaio de citometria de fluxo utilizando microesferas para o diagnóstico de Plasmodium vivax

Abstract

Malaria is an infectious-parasitic disease of great importance in global public health, related to high rates of morbidity and mortality, especially in tropical and subtropical regions. In Brazil, the Amazon region is the most affected, with the prevalence of infections caused by the species Plasmodium vivax, which is responsible for 85% of cases in the country, and Plasmodium falciparum. The development of new diagnostic methods continues to be of great importance for fighting this disease in search of its eradication. In the first chapter of this dissertation we present a review article, in which we highlight the main applications of flow cytometry tests based on microspheres for the detection of infectious and non-infectious diseases. In the second chapter, an original article was prepared in the format of a short communication, based on the development of a flow cytometry test using latex microspheres, aiming at the detection of the P. vivax lactate dehydrogenase antigen (PvLDH). Cytometry tests were performed on 50 samples from patients diagnosed with malaria caused by P. vivax and 40 samples from healthy individuals. When analyzed by the percentage of fluorescence labeling, the assay had a sensitivity of 64%, specificity of 97%, positive predictive value of 97%, and negative predictive value of 57%. By analyzing the mean fluorescence intensity (MFI), the assay sensitivity was 53%, specificity 89%, positive predictive value 95% and negative predictive value 33%. In both methods of analysis, there was a statistically significant difference between the groups analyzed (p-value < 0.0001). A high correlation (0.60) between the two methods and a low correlation between PvLDH concentration and parasite density were observed. The test showed more promising results when analyzed by the percentage of fluorescence labeling, being able to detect the PvLDH protein with high specificity. However, sensitivity still needs to be optimized, which would make it possible, among other applications, to use the test in serological assays to detect asymptomatic patients and to confirm the results of immunochromatographic tests.