title: How reliable are tests for trachoma?--a latent class approach.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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).
authors.affiliation: F I Proctor Foundation, University of California San Francisco, San Francisco, California 94143-0412, USA.
authors.forename: Craig W
authors.initials: CW
authors.lastname: See
authors.forename: Wondu
authors.initials: W
authors.lastname: Alemayehu
authors.forename: Muluken
authors.initials: M
authors.lastname: Melese
authors.forename: Zhaoxia
authors.initials: Z
authors.lastname: Zhou
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
authors.forename: Stephen
authors.initials: S
authors.lastname: Shiboski
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gaynor
authors.forename: John
authors.initials: J
authors.lastname: Eng
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Keenan
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Lietman
mesh_terms: D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000235:genetics / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000032:analysis*; D003941:Diagnostic Techniques, Ophthalmological; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D016133:Polymerase Chain Reaction; D015995:Prevalence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014141:Trachoma / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D004269:DNA, Bacterial