Emerging trends and Innovative strategies for the diagnosis of Leishmaniasis: A quantum leap from classical to modern era.

The genus Leishmania comprises a distinct group of species that exhibit distinct clinical features. Interestingly, this clinical variability frequently overlaps or intersects resulting in symptoms that don't follow typical patterns and often resemble those of unrelated diseases. Diagnosing leishmaniasis is challenging as current techniques exhibit several lacunae including cross-reactivity with other protozoal species, inability to discriminate between species, along with differential sensitivity and specificity. Thus, despite multiple methods that can clinically confirm leishmaniasis disease, there are pitfalls present and the diagnostic methods are still far from being ideal. Over the last two decades, the emergence of non-invasive immunological and molecular techniques have played a key role in transforming and advancing the diagnostic approaches used for leishmaniasis. Although antibody-detection diagnostics such as rK39 ELISA, direct agglutination tests, indirect fluorescent antibody tests and immunochromatographic strip tests are very sensitive, they cannot be used to detect prior infections or to distinguish between Leishmania species. Molecular methods such as PCR and LAMP assay have gained popularity because of their extraordinary sensitivity and specificity as well as their versatility in analysing varied samples. However, diagnosing relapses and co-infections associated with leishmaniasis continues to pose significant challenges. Both misdiagnosis and delayed diagnosis can significantly impact a patient's survival. Here, this systematic and comprehensive review provides an overview of both conventional and emerging diagnostic methods for Leishmania, including biosensors and AI-based tools. It highlights innovative strategies to bridge traditional and advanced methods, emphasizing that improved diagnostics are critical for effective disease detection, management and control.