Comparison of a qualitative immunochromatographic test with two quantitative serological assays for the detection of antibodies to Leishmania infantum in dogs

Abstract

Canine leishmaniosis is a disease caused by Leishmania infantum, a vector-borne parasite. Due to the zoonotic potential of canine leishmaniosis, infected dogs must be identified. Serological assays are the most common methods for the detection of L. infantum infection in dogs used in veterinary practice. The aim of the study was to assess the performance of a rapid immunochromatographic test ( FAST est LEISH ® , MEGACOR Diagnostik) for the detection of specific antibodies to that of the L. infantum in dog sera. The results were simultaneously compared using a commercial brand of indirect immunofluorescence antibody test and an in-house enzyme-linked immunosorbent assay as references. Between the two reference tests, 232 serum samples out of 244, produced concordant results while 12 exhibited discordant results. Of the 232 concordant samples, 121 were classified as L. infantum seropositive, and 111 samples were previously classified as L. infantum seronegative by a combination of the reference assays. All samples that were seropositive by the reference tests were also positive according to the rapid test, and only one sample that was seronegative according to the two reference assays was positive according to the rapid test. Compared with the reference tests, the rapid test sensitivity was 100%, specificity was 99.1%, accuracy was 99.6%, Cohen’s kappa coefficient was 0.99, and the area under receiver operating characteristic curve was 0.995. The FAST est LEISH ® is a rapid, qualitative in-clinic test with high sensitivity and specificity. Electronic supplementary material The online version of this article (10.1186/s13028-019-0473-1) contains supplementary material, which is available to authorized users.

Clinical, Molecular and Serological Diagnosis of Canine Leishmaniosis: An Integrated Approach

“…Sensitivity, specificity, negative and positive predictive values (NPV and PPV) were calculated for each molecular and serological technique, considering the combined results of each group of methods as a gold standard (molecular or serological). The gold standard was chosen on the proposition basis that when a reliable gold standard is not available, at least two different tests should be performed [6,36]. The agreement between LAMP and Rt-PCR was calculated using Cohen's κ statistic [37].…”

“…Moreover, a positive sample with a qualitative technique needs to be also analyzed with a quantitative technique (i.e., IFAT) in clinical studies to understand the difference between pre and post-treatment. Nevertheless, IFAT evaluation is subjective, and its results depend on the experience of the personnel [6]. In addition, sensitivity and specificity of serological tests are very variable in the literature, also considering the choice of a gold standard.…”

“…In addition, sensitivity and specificity of serological tests are very variable in the literature, also considering the choice of a gold standard. In fact, some authors considered the combination of at least two techniques [6,36], as in our study, while some other authors used a Bayesian method to evaluate the performances of the tests [10,40] In the last years, many molecular techniques have been developed for the diagnosis of leishmaniosis [25]. In particular, the Rt-PCR resulted very useful to evaluate follow-up, nevertheless, this molecular technique is not widely used due to its complexity, and it requires expensive laboratory equipment and expert staff [25,41].…”

“…In addition, sensitivity and specificity of serological tests are very variable in the literature, also considering the choice of a gold standard. In fact, some authors considered the combination of at least two techniques [ 6 , 36 ], as in our study, while some other authors used a Bayesian method to evaluate the performances of the tests [ 10 , 40 ]…”

“…CanL is characterized by a broad spectrum of clinical signs and degrees of severity, due to pathogenic mechanisms of Leishmania, and to the variable immune response of individuals. Hence, diagnosis is not easy and should be based on an integrated approach based on anamnesis, clinical signs, clinicopathological alterations, and usage of different laboratory techniques [5,6]. Moreover, early diagnosis of CanL is of great importance in order to perform an early and appropriate therapy and to prevent progression towards severe disease [7].…”