Parasitological diagnosis Only rarely can amastigotes be demonstrated in buffy coat preparations from peripheral blood. Biopsies of spleen (risky!), liver, lymph node or bone marrow (sternum) have to be taken and stained for the detection of amastigote parasites. Biopsies can be put into culture medium in which amastigotes transform to promastigotes and multiply. Molecular diagnosis Highly sensitive and specific nested PCR and real-time PCR methods have been developed to detect DNA in bone marrow or in biopsies. In underlying immunal suppression peripheral blood would be sufficient. Molecular methods are more sensitive than microscopy. Antigen detection No tests developed so far Antibody detection The detection of specific antibodies is a cornerstone of a diagnostic strategy in visceral leishmaniasis. ELISA and IFA tests have been standardized and are commercially available. For the field, a direct agglutination test (DAT) using a freeze-dried antigen, and an immunochromatographic dipstick test with a recombinant antigen (K39) are available. A recent meta-analysis revealed that both tests have high sensitivities (around 95%) but limitations in specificity (approx. 90%). Variations in the sensitivity of the dipstick test in different endemic areas ask for improvements.
Diagnostic strategies
To diagnose a symptomatic case If a case is suspected from clinical findings, the detection of circulating antibodies is the next diagnostic choice. Confirmation of the diagnosis is then done by PCR or if this is not available, by microscopy.
To screen an exposed population For epidemiological studies, the direct agglutination test (DAT) is a convenient choice for screening.
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