Sensitivity and specificity of parallel or serial serological testing for detection of canine Leishmania infection

In Brazil, human and canine visceral leishmaniasis (CVL) caused byLeishmaniainfantum has undergone urbanisation since 1980, constituting a publichealth problem, and serological tests are tools of choice for identifying infecteddogs. Until recently, the Brazilian zoonoses control program recommendedenzyme-linked immunosorbent assays (ELISA) and indirect immunofluorescence assays(IFA) as the screening and confirmatory methods, respectively, for the detection ofcanine infection. The purpose of this study was to estimate the accuracy of ELISA andIFA in parallel or serial combinations. The reference standard comprised the resultsof direct visualisation of parasites in histological sections, immunohistochemicaltest, or isolation of the parasite in culture. Samples from 98 cases and 1,327noncases were included. Individually, both tests presented sensitivity of 91.8% and90.8%, and specificity of 83.4 and 53.4%, for the ELISA and IFA, respectively. Whentests were used in parallel combination, sensitivity attained 99.2%, whilespecificity dropped to 44.8%. When used in serial combination (ELISA followed byIFA), decreased sensitivity (83.3%) and increased specificity (92.5%) were observed.Serial testing approach improved specificity with moderate loss in sensitivity. Thisstrategy could partially fulfill the needs of public health and dog owners for a moreaccurate diagnosis of CVL.