The role of rk39 serologic test in the diagnosis of visceral leishmaniasis in a Tertiary Hospital, Northern Ethiopia

Background: The study is done in Ayder Referral Hospital in Northern Ethiopia. Ethiopia is one of the countries where visceral leishmaniasis (VL) is endemic. Diagnosis of VL in Ethiopia is primarily based on rK39 immunochromatographic (rk39-ICT) strip. This test has been shown to have variable sensitivity and specificity in different countries. Hence the objective of the study is to determine the sensitivity and specificity of rk39-ICT in the diagnosis of VL in our set up. The study participants were VL suspected patients admitted to the hospital. A cross sectional study design was used. The study was conducted from January 14, 2013 to June 26, 2015. The rK39-ICT strip used was the InBios brand. Ethical clearance was obtained from the IRB of the college and written consent was obtained from the individual patients. Results: A total of 62 VL suspects were involved in the study. The mean age was 26.3 years (SD = 6.94 years) with a median age of 25.5 years. Sixty-one (98.4%) of the patients was males. The rK39-ICT was positive in 50 (80.6%) of the patients. Splenic aspiration was positive in 44 (71%) of the patients. In 37 (59.7%) of the patients both rK39 and splenic aspiration were positive. Thirteen (21%) of the patients had positive rK39 but negative splenic aspiration. Five (8.1%) of the patients had both negative rK39 and splenic aspiration however seven (11.3%) of the patients had rk39 negative but splenic aspiration positive. The sensitivity, specificity, positive predictive value and the negative predictive value of rK39-ICT, taking splenic aspiration as a gold standard test, is 84.1% (95% CI 69.9-93.4%), 27.8% (95% CI 9.7-53.5%), 74.0% (95% CI 60-85.4%) and 41.7% (95% CI 15.2-72.3%) respectively. Conclusion: Sensitivity of rK39-ICT is low and its specificity is poor in our set up. Significant number of patients with confirmed VL did not have travel history to endemic areas. We recommend that the rK39-ICT needs improvement for clinical use in our set up and case definition for visceral leishmaniasis in Ethiopia needs to be revisited.