Testing urine samples with rK39 strip as the simplest non-invasive field diagnosis for visceral leishmaniasis

Abstract

Diagnosis of visceral leishmaniasis (VL) is a major obstacle in the control of this disease. The rK39 strip-test using patient's blood is a breakthrough; however, it still requires a blood sample, which is a concern for safety in the field. We tried to simplify the test using the patient's urine instead of blood. To observe the sensitivity and specificity of the urine test in comparison with the blood test. We tested active and post-treatment VL patients, Post Kala azar dermal leishmaniasis (PKDL), VL/HIV and control subjects (healthy, disease suspects and diseased other than VL) with the rK39 strip-test using blood and urine samples. The level of agreement between the urine and blood testing was calculated by inter-rater agreement (kappa) statistics. Forty-two active VL, 40 treated VL, six PKDL, three VL/HIV and 139 controls (54 healthy, 21 disease suspects and 64 diseased other than VL) were tested. All VL-related cases showed positive results with urine as well as blood samples (100%). The urine testing was found to have 100% sensitivity and 86.33% specificity for the diagnosis of VL. Kappa statistic between the two methods was 0.916 (P<0.001). Urine testing had more false-positive results in comparison with blood testing (13.67% vs. 9.45%), but the test subjects were from VL-endemic areas and they might be exposed to Leishmania donovani infection. The present study has the potentiality of providing a new, yet simplest non-invasive screening tool for VL in remote rural areas.