Abstract. The aim of this study was to evaluate the accuracy of invasive and non-invasive tests for diagnosis of visceral leishmaniasis (VL) in a large series of human immunodeficiency virus (HIV)-infected patients. In this delayedtype cross-sectional study, 113 HIV-infected symptomatic patients were evaluated by an adjudication committee after clinical follow-up to establish the presence or absence of VL as the target condition (reference test). The index tests were recombinant K39 antigen-based immunochromatographic test (rK39), indirect fluorescent antibody test (IFAT), prototype kit of direct agglutination test (DAT-LPC), and real-time polymerase chain reaction (qPCR) in peripheral blood. Compared with parasitological test and adjudication committee diagnosis or latent class model analyses, IFAT and rk39 dipstick test presented the lowest sensitivity. DAT-LPC exhibited good overall performance, and there was no statistical difference between DAT-LPC and qPCR diagnosis accuracy. Real-time PCR emerges as a less invasive alternative to parasitological examination for confirmation of cases not identified by DAT.
Peripheral blood samples of 138 co-habitants from 25 families with recently diagnosed cases of visceral leishmaniasis in the Metropolitan Region of Belo Horizonte, Minas Gerais, Brazil, were analyzed by indirect fluorescent antibody test (IFAT), rK39 and Leishmania chagasi Enzyme Linked Immunosorbent Assay (ELISA), intradermal skin-test and Polymerase Chain Reaction (PCR) over a 12-month period. The cumulative positivity was significantly higher by PCR (29.7%) than by IFAT, rK39 ELISA, L. chagasi ELISA and intradermal skin-test (5.1%, 6.5%, 14.5% and 2.9%, respectively). In addition, the cytokine profile was measured in 16 of the 138 volunteers, of whom eight were asymptomatic carriers and eight were non-infected co-habitants. The innate immunity cells from asymptomatic carriers displayed, upon in vitro antigenic stimulation, a modulated increase in cytokine synthesis that was distinct from that observed in non-infected volunteers. This study suggests that the identification of a large proportion of asymptomatic carriers is facilitated when more than one diagnostic method is applied and that a mixed pattern of immune response is correlated with clinical status of asymptomatic individuals. These observations suggest also that asymptomatic infection by L. chagasi is a frequent event and that control programs could benefit by including this indicator in their interventions.
The diagnosis of visceral leishmaniasis (VL) is still a major problem in Brazil and several other countries where the disease is endemic. The use of an easy-to-use and interpret, sensitive, and specific method that requires no complex infrastructure or specialized professionals, such as direct agglutination test (DAT) and the rK39-based rapid immunochromatographic test may enhance the diagnosis of disease. This study evaluated the performance of a rapid test (DiaMed- IT-LEISH®) and the DAT for the diagnosis of VL in 213 parasitologically confirmed cases and 119 controls with clinical suspicion of VL and confirmation of another etiology. The sensitivities and specificities of the rapid test were 93% and 97%, respectively and those of the DAT were 90% and 96%, respectively. The positive predictive values of the rapid test and the DAT were 98% and 97%, respectively and the negative predictive values were 89% and 84%, respectively. The Kappa index showed agreement between both methods classified as substantial (0.77). This study showed that the DAT and the rapid test can be used to diagnose VL in Brazil, following a pilot study for implementation of the rapid test in the health services.
In order to estimate the magnitude of Leishmania/HIV co-infection, patients with HIV/AIDS at the Brasilia University Hospital, DF, Brazil were used as subjects in a cross-sectional study. One hundred and sixty-three patients were enrolled, seven of whom had visceral leishmaniasis (VL). One hundred and twelve patients (68.7%) were men; 155 (95.1%) had been exposed to HIV infection through unprotected sex. The median age was 37 years (range: 20-74) and the median CD4+ lymphocyte count was 314 cells/microl (range: 2-1600). Symptomatic patients underwent bone marrow evaluations through direct examination of Giemsa-stained films, parasite culture and PCR assay. Blood samples were evaluated by means of an indirect immunofluorescent antibody test (IFAT), an ELISA using a soluble antigen of L. chagasi (ELISA), an ELISA with the rK39 antigen (ELISA-rK39) and a PCR targeted to the kDNA region and to the internal transcribed spacer 1 of the rDNA gene. The proportion of positive results was 2.4% for the IFAT, 12.3% for the ELISA and 4.9% for the rK39 tests. The estimated prevalence was 16%. The PCR in the blood was positive in three patients (1.8%). The prevalence of Leishmania spp. infection is high among HIV patients attending this Brazilian center suggesting that they should be routinely investigated for VL infection.
Abstractobjective To estimate the sensitivities and specificities of different diagnostic tests for visceral leishmaniasis (VL) using latent class analysis (LCA). conclusions Considering the lack of an adequate reference standard, LCA proved to be a useful tool in validating diagnostic methods for VL. The DAT and the rK39 rapid test showed better performance. Thus, clinically suspected cases of VL in a Brazilian endemic area could be treated based on the positivity of one of these tests.
These results highlight the need for the revision of algorithm for VL diagnostic in Brazil. Replacements of IFAT with DAT-LPC, Kalazar Detect with IT LEISH and bone marrow aspirate performed in a hospital setting with PCR are cost-effective public health measures.
O teste imunocromatográfico rápido IT-LEISH® (DiaMed IT-LEISH®) foi validado para o diagnóstico da leishmaniose visceral (LV) em quatro áreas endêmicas do Brasil. O desempenho do IT-LEISH® foi comparado ao da reação de imunofluorescência indireta; e ao da reação imunoenzimática, usando-se antígeno solúvel de Leishmania chagasi e recombinante K39 (rK39). O estudo incluiu 332 pacientes com quadro clínico sugestivo de LV: 213 casos de LV confirmados parasitologicamente; e 119 não-casos, com confirmação de outra etiologia. O teste IT-LEISH® apresentou sensibilidade de 93% e especificidade de 97%. As técnicas RIFI (imunofluorescência indireta), ELISA L. chagasi e ELISA rK39 apresentaram sensibilidade de 88%, 92% e 97% e especificidades de 81%, 77% e 84%, respectivamente. Os resultados confirmam a validade do teste IT-LEISH® para o diagnóstico da LV no Brasil.
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