Latent-Class Methods to Evaluate Diagnostics Tests for Echinococcus Infections in Dogs

Abstract

BackgroundThe diagnosis of canine echinococcosis can be a challenge in surveillance studies because there is no perfect gold standard that can be used routinely. However, unknown test specificities and sensitivities can be overcome using latent-class analysis with appropriate data.MethodologyWe utilised a set of faecal and purge samples used previously to explore the epidemiology of canine echinococcosis on the Tibetan plateau. Previously only the purge results were reported and analysed in a largely deterministic way. In the present study, additional diagnostic tests of copro-PCR and copro-antigen ELISA were undertaken on the faecal samples. This enabled a Bayesian analysis in a latent-class model to examine the diagnostic performance of a genus specific copro-antigen ELISA, species-specific copro-PCR and arecoline purgation. Potential covariates including co-infection with Taenia, age and sex of the dog were also explored. The dependence structure of these diagnostic tests could also be analysed.Principle findingsThe most parsimonious result, indicated by deviance-information criteria, suggested that co-infection with Taenia spp. was a significant covariate with the Echinococcus infection. The copro-PCRs had estimated sensitivities of 89% and 84% respectively for the diagnoses of Echinococcus multilocularis and E. granulosus. The specificities for the copro-PCR were estimated at 93 and 83% respectively. Copro-antigen ELISA had sensitivities of 55 and 57% for the diagnosis of E. multilocularis and E. granulosus and specificities of 71 and 69% respectively. Arecoline purgation with an assumed specificity of 100% had estimated sensitivities of 76% and 85% respectively.SignificanceThis study also shows that incorporating diagnostic uncertainty, in other words assuming no perfect gold standard, and including potential covariates like sex or Taenia co-infection into the epidemiological analysis may give different results than if the diagnosis of infection status is assumed to be deterministic and this approach should therefore be used whenever possible.

Global Distribution of Alveolar and Cystic Echinococcosis

“…In Shiqu County, western Sichuan Province, prevalence was 12% of 372 dogs purged with arecoline, probably closer to 15% when adjusted for the insensitivity of purgation (Budke et al, 2005a(Budke et al, , 2005bHartnack et al, 2013). Further studies in the same area found 23% of 142 samples of dog faeces positive for E. multilocularis (Vaniscotte et al, 2011).…”

Test characteristics of milk amyloid A ELISA, somatic cell count, and bacteriological culture for detection of intramammary pathogens that cause subclinical mastitis

“…We ran 3 chains from 3 different starting points as used by Hartnack et al (2013) and screened for convergence.…”

“…An alternative approach is to estimate diagnostic accuracy with Bayesian latent class modeling, using results from at least 3 different diagnostic tests of the same sample (Branscum et al, 2005;Berkvens et al, 2006;Hartnack et al, 2013). The aim of this study was to estimate the diagnostic Se and Sp of SCC, MAA-ELISA, and BC for the diagnosis of subclinical mastitis in dairy cows using Bayesian latent class modeling.…”

Evaluation of faecal flotation methods followed by species-specific PCR for detection of Echinococcus multilocularis in the definitive hosts

“…This sensitivity is similar to, or lower than that of other postmortem and antemortem diagnostic techniques (Table IV). Even an identical diagnostic test may have a considerable difference in performance between different study populations (Hartnack et al 2013). As the study populations were not identical, the comparison of the sensitivities of the various diagnostic techniques is difficult.…”

“…As no perfect gold standard is available for the antemortem diagnosing of E. multilocularis infection (Table IV), multiple tests should ideally be used in the population of interest (Hartnack et al 2013). The improved faecal flotation might also be a candidate for multiple testing of domesticated and protected wild carnivore populations.…”