Diagnostic Accuracy of Two rK39 Antigen-Based Dipsticks and the Formol Gel Test for Rapid Diagnosis of Visceral Leishmaniasis in Northeastern Uganda

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Abstract
The development of an accurate, practical, and affordable diagnostic test is essential to improve the management of visceral leishmaniasis (VL) in remote health centers. We evaluated the Formol Gel test (FGT) and two rK39 antigen-based dipsticks, the DUAL-IT L/M, and the Kalazar Detect for VL diagnosis in Amudat Hospital in Uganda. The DUAL-IT L/M was also evaluated for the diagnosis of malaria. All patients clinically suspect of VL were prospectively included in the study between October 2003 and March 2004. The gold standard used to define a VL case was a positive spleen aspirate or a direct agglutination test titer of >1:12,800 with an appropriate clinical response to antileishmanial therapy. A total of 131 VL and 112 non-VL patients were included in the analysis. The DUAL IT L/M was found to be more sensitive than the Kalazar Detect: 97% (95% confidence interval [95%CI] = 92 to 99%) versus 82% (95%CI = 74 to 87%). The Kalazar Detect and the DUAL IT L/M were highly specific (99% [95%CI = 95 to 100%] and 97% [95%CI = 92 to 99%], respectively). The FGT lacked both sensitivity (66% [95%CI = 57 to 73%]) and specificity (90% [95%CI = 83 to 94%]). The sensitivity of the DUAL IT L/M for malaria was only 57% (95%CI = 37 to 76%). The two rK39 dipsticks can be used for diagnostic confirmation of VL in this region. The DUAL-IT L/M without its malaria diagnostic component (DiaMed-IT LEISH) will be adopted as first-line test for VL in Uganda.