Diagnostic effectiveness of urine and saliva samples for detection of visceral leishmaniasis using rK39-based immunochromatographic test, Northwest, Ethiopia

A whole blood/serum by rK39immunochromatographic test are the most widely used biological samples for diagnosis/screening of visceral leishmaniasis (VL). However, sample collection is relatively invasive and more difficult to apply in children and during field surveillance. Finding of alternative, non-invasive and easy surveillance samples like urine and saliva for VL diagnosis is vital. Thus, study was amid to evaluate the effectiveness of urine and saliva samples for the diagnosis of VL by rK-39 based rapid test using serum rK39 value as gold standard test.

Institutional based cross-sectional study was conducted from April 2022 to July 2022 in Northwest Ethiopia. Blood, saliva, and midstream urine samples were collected among VL confirmed patients and non endemic healthy controls. Data was entered in to Epi-data (version 4.2) and analyzed using STATA (version 21). The diagnostic performance of both samples were evaluated in terms of sensitivity, specificity and area under the curve (AUC) using serum rK-39 test results as gold standard. Kappa statistics was used to evaluate the agreement of urine and saliva rk39-based rapid test result with serum sample gold standard test.

A total of 63 participants (32 confirmed VL patients and 31 healthy control individuals were enrolled in the study. The sensitivity, specificity and area under the curve (AUC) of urine by rK-39 based rapid test were found to be 87.5% (79.3–95.67%), 96.7% (92–100%) and 0.92 respectively. Similarly, sensitivity, specificity and area under the curve (AUC) of saliva by rK39 rapid test were found to be 90.6% (83.4–97.82%), 100%, and 0.95. The kappa agreement of urine and saliva with reference serum sample were strong (k = 0.84) and (k = 0.904) respectively.

In this study, both urine and saliva samples showed a promising finding to be a serum alternative specimen for the diagnosis of VL mainly in areas lacking advanced medical facilities and skilled personnel. Yet, clinical practice needs further multicenter study with large sample size inclusive of both symptomatic and asymptomatic participants.