Visceral leishmaniasis (VL) or kala-azar is one of the most important parasitic tropical diseases. Untreated, VL is fatal; hence early and accurate diagnosis is essential. Two methods are commonly used in the routine diagnosis of the disease: parasitology and serology.

Parasitology
Parasitological testing comprises microscopical examination of tissue smears/aspirates and parasite culture. The latter method may be more sensitive and reliable than microscopy in diagnosis of VL, especially when there are few parasites present. Culture may give information on the viability of the parasite, which can be important in evaluating VL chemotherapy. The parasitological methods are highly specific, but their sensitivity can be as low as 50–60% depending on the type of tissue and method employed. Therefore, serology is often used in the diagnosis of VL.

Serology
The direct agglutination test (DAT) remains the first-line diagnostic tool in Sudan as it appears to be a simple and economical test with high sensitivity and specificity. The test is very suitable for use in the field. The development of a freeze-dried (FD) antigen increased the applicability of the test under rural conditions as, in contrast to liquid antigen, a cold chain for preserving the antigen is not necessary.

Many studies have been conducted towards the sensitivity and specificity of the test and in general it is accepted that the DAT is the most robust of currently available tests for use in clinical settings in disease endemic countries. Furthermore, cost-effectiveness analysis of VL diagnostic-therapeutic strategies demonstrated DAT as the most effective test when used after screening of patients based on clinical case definition.