Performance of rK39 immunochromatography and freeze-dried direct agglutination tests in the diagnosis of imported visceral leishmaniasis

Abstract

Visceral leishmaniasis (VL) is one of the neglected tropical diseases that require a global policy for integrated control programs. The disease is fatal if untreated, affects ∼500,000 persons/year, and is most prevalent in poor countries. Treatment is expensive and carries a risk of toxicity. Therefore, sensitive and specific diagnosis of VL is crucial to avoid under- or overdiagnosis. Selecting an appropriate serological diagnostic test is an issue of controversy and depends on geographic location. The study aimed to evaluate the performance of two serological techniques: recombinant antigen K39 (rK39)-immunochromatographic (IC) lateral flow assay (InBios, USA) that uses a recombinant Leishmania antigen K39 and the specific IgG detection by direct agglutination test (DAT, for the diagnosis of imported VL in non-endemic region (Saudi Arabia). The diagnostic accuracy of the two assays was assessed using bone marrow aspiration, direct microscopic examination, and culture on NNN agar as the "gold standard". The bone marrow specimens from Indian, Sudanese, and Bengali patients (n = 98) with suspected VL features were cultured. Thirty-five specimens were positive (36%). The sensitivity and specificity of rK39-IC test were 89% (95% CI 78-99) and 92% (95% CI 85-99), respectively. DAT (with cutoff ≥1:1,600) showed comparable results (sensitivity 94%; 95% CI 87-101 and specificity 95%; 95% CI 90-100). To conclude, the performance of rK39-IC test and DAT is comparable. Both tests are moderately sensitive and specific and could be used to facilitate the global drive to eliminate this disease. The rK39-IC test is a rapid, easy-to-perform test and can be used as a point-of-care diagnostic method.

Cross-Sectional Study to Assess Risk Factors for Leishmaniasis in an Endemic Region in Sri Lanka

“…The rK39 rapid diagnostic test (RDT) (InBios Corporation, Seattle, WA), which was used for diagnosis of VL, is a rapid immunochromatographic strip assay used to qualitatively detect antibodies against L. donovani to the K39 antigen in human serum. 1,25,33,34 The test kit is prepared with recombinant rK39 Leishmania sp. antigen and is used widely in VL-endemic countries in community surveys to determine the subclinical VL case incidence and the presence of antibodies against the K39 antigen of Leishmania spp.…”

“…in the population. 1,33,34 Blood (1.0 mL) was obtained by venipuncture from participants more than 12 years of age and 3-5 drops of blood was obtained by finger prick from persons 2-12 years of age by a doctor or a trained nurse under aseptic conditions using sterile equipment. Serum was separated by centrifugation.…”

The Diagnostic Accuracy of Direct Agglutination Test for Serodiagnosis of Human Visceral Leishmaniasis: A Systematic Review with Meta-analysis

“…The reference method for diagnosis of VL in all studies was a positive result on microscopic examination and/or culture of lymph node, bone marrow, or spleen aspirates. Diagnosis was con rmed by detection of parasites in culture (14)(15)(16)(17).…”

The Diagnostic Accuracy of Direct Agglutination Test for Serodiagnosis of Human Visceral Leishmaniasis: A Systematic Review with Meta-analysis

“…The reference method for diagnosis of VL in all studies was a positive result on microscopic examination and/or culture of lymph node, bone marrow, or spleen aspirates (15)(16)(17).…”

“…Among 24 studies, 20 records were quali ed for meta-analysis. All studies except 2 reports (one cohort (28) and one casecontrol (15) were cross sectional studies evaluating the diagnostic accuracy of DAT and meta-analysis was performed on all cross sectional studies evaluating the diagnostic accuracy of DAT. Three studies were excluded because there was zero cell and sensitivity and/or speci city cannot be calculated.…”