Evaluation of the performance of rapid tests based on recombinant antigens for the diagnosis of human visceral leishmaniasis

Introduction:Early diagnosis of Human Visceral Leishmaniasis (HVL) is the main pillar for adequate clinical management and epidemiological control of the disease.In Brazil, the Ministry of Health has recommended, since 2011, the use of rapid tests (RT) based on the rK39 antigen in the public health network.However, the constant emergence of new diagnostic inputs and the variability in the performance of different recombinant antigens make it essential to evaluate these tools alongside conventional serological methods. Objectives:The objective of this study was to evaluate the diagnostic agreement of five rapid tests (TR A, B, C, D, and E), based on different recombinant antigens, comparing them to the enzyme-linked immunosorbent assay with soluble Leishmania major antigen (EIE Lm).Methodology: A total of 103 human serum samples previously characterized by EIE Lm were selected, 79 of which were reactive and 24 were non-reactive.The analyses followed the manufacturers' protocols, allowing the calculation of sensitivity, specificity, global agrment, and the Kappa coefficient. Results:The results revealed significant variations in performance: TR A presented the best overall performance, with an agreement index of 93% and a Kappa of 0.80, demonstrating high sensitivity (97%) and specificity (79.2%).The RT D stood out for its maximum sensitivity (100%), with a Kappa of 0.78 and an overall agreement of 93%.Tests B and C showed good agreement (Kappa = 0.74; 90% overall), while RT E showed the weakest performance, with moderate agreement (Kappa = 0.48) and low specificity (54%), which increases the risk of false-positive results. Conclusion:The partial conclusions indicate that the nature of the recombinant antigen employed directly impacts the diagnostic accuracy.While the TR A is more suitable for confirmatory purposes due to its balance between parameters, the TR D is a superior screening tool due to its absolute sensitivity.The strategic need to adopt protocols with complementary tests to increase diagnostic safety is emphasized.Although the study has a limitation of the small number of negative samples, the data reinforce the importance of continuous validation of new technologies for the improvement of public health policies to combat HVL.