Dataset Information

How reliable are tests for trachoma?--a latent class approach.

ABSTRACT: Tests for ocular Chlamydia trachomatis have not been well characterized, because there is no gold standard test. Latent class analysis (LCA) was performed to estimate the sensitivity and specificity of laboratory and clinical tests for trachoma in the absence of a gold standard.Individual data from pretreatment, hyperendemic areas in Ethiopia were used. A clustered LCA was performed for three diagnostic tests: PCR and WHO simplified criteria grades of follicular trachoma (TF) and intense trachomatous inflammation (TI).Data from 2111 subjects in 40 villages were available. TF was estimated to be 87.3% (95% CI, 83.3-90.1) sensitive and 36.6% (95% CI, 23.6-40.3) specific; TI was estimated to be 53.6% (95% CI, 46.1-88.0) sensitive and 88.3% (95% CI, 83.3-92.0) specific, and PCR was estimated to be 87.5% (95% CI, 79.9-97.2) sensitive and 100% (95% CI 69.3-100) specific.LCA allows for an estimate of test characteristics without prior assumption of their performance. TF and TI were found to act in a complementary manner: TF is a sensitive test and TI is a specific test. PCR is highly specific but lacks sensitivity. The performance of these tests may be due to the time course of ocular chlamydial infection, and for this reason, results may differ in areas of low prevalence or recent mass treatment (ClinicalTrials.gov number, NCT00221364).

SUBMITTER: See CW

PROVIDER: S-EPMC3176003 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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How reliable are tests for trachoma?--a latent class approach.

See Craig W CW Alemayehu Wondu W Melese Muluken M Zhou Zhaoxia Z Porco Travis C TC Shiboski Stephen S Gaynor Bruce D BD Eng John J Keenan Jeremy D JD Lietman Thomas M TM

Investigative ophthalmology & visual science 20110803 9

<h4>Purpose</h4>Tests for ocular Chlamydia trachomatis have not been well characterized, because there is no gold standard test. Latent class analysis (LCA) was performed to estimate the sensitivity and specificity of laboratory and clinical tests for trachoma in the absence of a gold standard.<h4>Methods</h4>Individual data from pretreatment, hyperendemic areas in Ethiopia were used. A clustered LCA was performed for three diagnostic tests: PCR and WHO simplified criteria grades of follicular t ...[more]

PMID: 21685340

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Project description:Rift Valley Fever is an important zoonotic viral disease of livestock occurring across much of Africa causing acute febrile illness, abortion, and neonatal death in livestock particularly sheep and cattle and a range of disease in humans from mild flu-like symptoms to more severe haemorrhagic fever and death. Understanding the epidemiology requires well-evaluated tools including antibody detection ELISAs. It is well-recognized that tests developed in one population do not necessarily perform as well when used in different populations and it is therefore important to assess tests in the populations in which they are to be used. Here we describe the performance of a commercial RVF ELISA (ID.Vet) and an in-house plaque reduction neutralization test (PRNT80). A Bayesian no gold standard latent class model for two tests and ?2 populations based on the Hui-Walter model was used to estimate the test parameters using a range of populations based on geographical separation and age to assess consistency of performance across different sub-populations. The ID.Vet ELISA had an estimated diagnostic sensitivity (Se) of 0.854 (0.655-0.991 95%BCI) and specificity (Sp) of 0.986 (0.971-0.998 95%BCI) using all the data and splitting the population by geographical region compared to 0.844 (0.660-0.973 95%BCI) and 0.981 (0.965-0.996 95%BCI) for the PRNT80. There was slight variation in the mean Se and Sp in different sub-populations mainly in Se estimates due to small numbers of positives in the sub-populations but the 95% BCI generally overlapped suggesting a very consistent performance across the different geographical areas and ages of animals. This is one of few reports of serological evidence of RVF in Central Africa and strongly suggests the virus is actively circulating in this cattle population. This has important public health implications and RVF should be considered as a differential in both livestock disease cases as well as human febrile cases in West and Central Africa not just East Africa. We also demonstrate that the performance of the commercial ELISA is comparable to the PRNT80 but has the advantages of speed, lower cost and no containment needs making it a much more useful test for low and middle income settings (LMICs).

Project description: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.

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How reliable are tests for trachoma?--a latent class approach.

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How reliable are tests for trachoma?--a latent class approach.

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