Leishmania antibodies are detected using serologic tests on blood or serum: rapid rK39 immunochromatographic tests, direct agglutination (DAT), ELISA, and indirect immunofluorescence (IFAT). These assays are most useful for visceral leishmaniasis, with sensitivity varying by test and region. When serology is inconclusive, diagnosis can be confirmed by microscopy or PCR on bone marrow, spleen, skin, or blood samples.

Confirmatory diagnosis of kala-azar (visceral leishmaniasis) requires demonstration of Leishmania parasites in tissue aspirates—most commonly bone marrow, splenic or lymph‑node smears—by microscopy or culture. PCR on blood or tissue provides high sensitivity and can confirm infection. rK39 rapid tests help screening, but parasite visualization or PCR is needed for a definitive diagnosis.

The main antibody used in leishmaniasis diagnostics is anti‑rK39 (IgG), detected by rapid tests for visceral leishmaniasis. Other serologic assays — direct agglutination test (DAT) and ELISA — also detect anti‑Leishmania IgG. Serology is helpful for visceral disease but less reliable for cutaneous leishmaniasis; results should be interpreted alongside clinical and parasitological findings.

Kala-azar (visceral leishmaniasis) is caused by protozoa of the Leishmania donovani complex. In South Asia and East Africa the main species is Leishmania donovani; in the Mediterranean, Middle East and the Americas the disease is usually due to Leishmania infantum (formerly L. chagasi). The parasites are transmitted to humans by infected female sandflies.

The first signs of leishmaniasis depend on the form. Cutaneous disease typically begins as a small red papule at the sandfly bite that slowly enlarges into a painless ulcer with raised edges; nearby lymph nodes may swell. Visceral leishmaniasis starts with prolonged fever, weight loss, fatigue, night sweats and progressive enlargement of the spleen and liver. Mucocutaneous infection causes nasal or oral mucosal congestion and ulceration.

Costs vary widely by country and test. rK39 rapid tests in endemic areas typically cost about $1–10 (≈₹100–800 in India) in private settings. Serology (ELISA/DAT) or PCR ranges ≈$10–60 (≈₹500–2,500). Invasive confirmation (bone‑marrow/splenic aspiration with microscopy) and hospital fees can be $25–150 (≈₹2,000–10,000). Public health programs often provide testing free or subsidized.