No One-Size-Fits-All for Serological Tests for Human Visceral Leishmaniasis

By Reuters Staff

July 26, 2019

NEW YORK (Reuters Health) - The accuracy of serological tests for human visceral leishmaniasis varies by methodology, manufacturer, and patient group, researchers from Brazil report.

The gold standard for diagnosis of human visceral leishmaniasis (VL) is the demonstration of Leishmania parasites in bone marrow aspirate or in other biological specimens. A wide range of serological tests are used for the diagnosis of VL, but no study has compared the performance of these tests under the same conditions and in the same population.

Dr. Mariana Lourenco Freire from Instituto Rene Rachou, Fundacao Oswaldo Cruz, in Belo Horizonte, and colleagues compared the performance of six commercial kits (three enzyme-linked immunosorbent assays, or ELISAs, two immunofluorescence antibody tests, or IFATs, and one immunochromatographic test, or ICT), one ICT not commercially available in Brazil and one in-house direct agglutination test (DAT-LPC) not yet marketed.

Accuracy rates differed by HIV status and by age group, the team reports in PLoS Neglected Tropical Diseases, online July 18.

Among individuals without HIV infection, the greatest accuracy was obtained with the French-manufactured ICT IT LEISH (96.2%) and with the in-house DAT-LPC (95.6%). For people infected with HIV, DAT-LPC (89.6%) and the German-manufactured ELISA Ridascreen Leishmania Ab (84.4%) worked best.

Most tests provided similar sensitivity, specificity and accuracy across age groups, but the U.S.-manufactured ICT Kalazar Detect had significantly lower sensitivity among children under 3 (86.2%) than among older children (96.1%).

Test sensitivities varied widely within and across methodologies, especially among HIV-infected patients.

"These results have direct implication in public health care policies in Brazil," the researchers conclude. "In addition to confirming the high performance of rapid immunochromatographic tests in general, the results show important exceptions, people living with HIV and children younger than 3 years old, specific groups in which a rapid test cannot be used to rule out the VL diagnosis safely. For these groups, a specific algorithm is required, and DAT-LPC emerges as the best performing serological test, which adds to its advantage in terms of national autonomy in production."

"In addition, these results suggest the presence of significant differences in the performance of tests from different manufacturers using the same methodology, which reinforces the need for local validations of the different tests before their use in large scale," they note.

"Our findings highlight the need for more stringent criteria for the registration of diagnostic products in Brazil, including the requirement to carry out validation studies before marketing," the authors add. "In a future, broader analysis, in addition to performance, other aspects of these tests should be considered before a diagnostic strategy is defined, such as cost-effectiveness, national production/autonomy and accessibility."

The study did not have commercial funding, and the researchers declared no conflicts of interest

Dr. Freire did not respond to a request for comments.


PLoS Negl Trop Dis 2019.