Question

Visceral leishmaniasis has a very high case fatality rate but is difficult to diagnose: bone marrow biopsy, one of the best diagnostic methods, is expensive and is often associated with serious side effects. If you were developing a new diagnostic for this disease, would you be more interested in maximizing sensitivity or specificity? Why?

Answer 1

Sensitivity = Ability to detect minute quantities of a substance

Specificity = Ability to distinguish a signle substance from a mixture.

Viral leishmaniasis is difficult to detect due to low viral count in the lesion. The infection symptoms are also not highly specific to leishmaniasis (Symptoms such as loss of weight, fever, diarrhoea and cough are common to many infections such as malaria, typhoid and tuberculosis)

Leishmania is very rarely found in the peripheral blood.

The infection is directly confirmed only by microscopic observation of spleen, bone marrow and lymph node aspirates.

Hence, the new technique must be aimed to improving the sensitivity of detecting molecular markers even at very low concentrations.