Development and assessment of loop-mediated isothermal amplification [LAMP] assay for the diagnosis of human visceral leishmaniasis in Iran

ABSTRACT

Parasitological methods for the diagnosis of Visceral leishmaniasis [VL] require invasive procedures, so serological and molecular approaches have been developed but are not generally applicable in the field. We evaluated a loop mediated isothermal amplification [LAMP] assay using blood from VL patients and compared it to nested PCR. Forty-seven subjects with clinical features [fever, hepatosplenomegaly and anemia] were confirmed positive for VL by the direct agglutination test [DAT] at titers >3200. Forty DAT negative individuals from non-endemic areas with no clinical signs or symptoms of VL served as controls. A LAMP assay was performed using a set of six primers targeting leishmania infantum kinetoplast DNA [kDNA] minicircle gene under isothermal [64 degree C] conditions. For nested PCR we used primers targeting the kDNA minicircle gene. The LAMP assay provided a detection limit of 1 parasite in 1 ml of j peripheral blood and detected L. infantum DNA in 44 of 47 DAT-confirmed VL cases, with diagnostic sensitivity of 93.6% [95% CI]. No L. infantum DNA was amplified in controls, indicating a specificity of 100%. The nested PCR yielded sensitivity of 96% [95% CI] and a specificity of 100% [95% CI]. The LAMP assay gave results similar to those of nested PCR but in a shorter time. The LAMP method is simple; requires no sophisticated equipment; has a short reaction time; and results, indicated by turbidity of the reaction mixture, are observable with the naked eye