Utility of smear examination, culture, and serological tests in the diagnosis of visceral leishmaniasis/post-kala-azar dermal leishmaniasis at National Centre for Disease Control, Delhi.

A range of assays have been developed to detect specific antileishmanial antibody, such as rK 39 immunochromatographic test (ICT), KE 16 ICT, ELISA test, and indirect immunofluorescent antibody test (IFAT), which play a crucial role in serological diagnosis of visceral leishmaniasis (VL). However, limited published reports are available on the utility of serological test (IFAT test/rk 39), smear examination, and culture in the diagnosis of VL and post-kala-azar dermal leishmaniasis (PKDL) in our country. We present utility of serological test (IFAT test/rK 39), smear examination for Leishmania donovani (LD) bodies, and culture in 2589 samples from 2294 VL/PKDL suspected patients (January 2009-December 2019) tested in Centre for Arboviral and Zoonotic diseases, National Centre for Disease Control, New Delhi, India, for laboratory diagnosis of VL/PKDL. A total of 80/553 (14.4%) cases were confirmed of VL (74/522 cases by demonstration of LD bodies in bone marrow smear examination, 5/12 in splenic smear examination 1/19 by culture) and 4/21 (19.0%) cases were confirmed of PKDL (demonstration of LD bodies in slit skin smear examination. In our study 197/1368 (14.4%) cases were diagnosed positive by IFAT, 34/646 (5.2%) cases by rk 39 ICT for VL/PKDL by demonstration of specific antileishmanial antibodies. As the goal of elimination of VL as a public health problem is approaching, apart from serological tests such as rk 39 and IFAT, direct methods of detection such as (parasitic demonstration in BM smear, culture, and molecular tests) for Leishmania may play a crucial role for achieving a correct diagnosis and treatment. We also concluded that IFAT though not field-friendly, its optimal use as an adjunct test with BM smear in all stages of infections may be required. Further rk39 is a simple, reliable, noninvasive, and field-friendly test for diagnosis VL, especially in endemic areas.