title: A systematic review on TST and IGRA tests used for diagnosis of LTBI in immigrants.
abstract: BACKGROUND
  High immigration rates from tuberculosis (TB) endemic countries to low-incidence countries have caused new TB guidelines in these countries to reconsider latent TB infection (LTBI) screening in these immigrants.
  
  
  OBJECTIVE
  We performed a systematic review with the primary outcome of evaluating the number of cases recommended LTBI treatment with the tuberculin skin test (TST) or interferon gamma release assay (IGRA). Secondary objectives were to examine prevalence of positive LTBI diagnostic tests stratified by age and incidence of TB in country of origin.
  
  
  METHODS
  We performed a systematic search of seven electronic databases for studies assessing TST and/or IGRA performance in immigrant populations to low incidence countries. Demographics, LTBI diagnosis, longitudinal TB development, and test result data were the primary data extracted from the studies. Prevalence of positive test data was stratified by age and country of origin. Studies were evaluated using a modified SIGN checklist for diagnostic studies. Data was compared using Fisher's exact test or χ (2) test, where appropriate.
  
  
  RESULTS
  Our literature search yielded 51 studies (n = 34 TST, n = 9 IGRA, n = 8 both). Recommendation of LTBI treatment was less common in those tested with an IGRA compared to TST (p < 0.0001), while long-term development of active TB appears higher in those with a positive IGRA. There was no difference in the sensitivity and specificity of the IGRA and TST for prevalent TB (p > 0.05). Prevalence of a positive test was significantly lower in those who were <18 years of age compared to those ≥18 years of age (p < 0.0001) and those from low TB incidence countries compared to high incidence countries (p < 0.0001) for both TST and IGRA. When comparing the two tests within the 2 subgroups: age and TB incidence in country of origin, the prevalence of positive results was significantly lower for the IGRA than the TST (p < 0.0001).
  
  
  CONCLUSIONS
  The number of available studies evaluating the IGRA and longitudinal active TB development in those tested limits this study.
  
  
  CONCLUSIONS
  Prevalence of positive test results were significantly lower in immigrants who were tested with an IGRA, resulting in fewer immigrants being recommended for LTBI treatment compared to TST. Coupled with comparable performance for detecting prevalent TB cases, the IGRA appears to exhibit better specificity than the TST and may be preferred as the standard of care for detecting LTBI in immigrants moving to low TB incidence countries.
authors.affiliation: University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.
authors.forename: Jonathon R
authors.initials: JR
authors.lastname: Campbell
authors.forename: Jane
authors.initials: J
authors.lastname: Krot
authors.forename: Kevin
authors.initials: K
authors.lastname: Elwood
authors.forename: Victoria
authors.initials: V
authors.lastname: Cook
authors.forename: Fawziah
authors.initials: F
authors.lastname: Marra
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000453:epidemiology; D000367:Age Factors; D001208:Asia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data*; D019353:Endemic Diseases; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D008877:Middle East / Q000453:epidemiology; D012680:Sensitivity and Specificity; D014374:Tuberculin Test