title: Screening travellers to high-endemic countries for infection with Mycobacterium tuberculosis using interferon gamma release assay; a prospective study.
abstract: BACKGROUND
  International travel from low-incidence to high-incidence countries for tuberculosis (TB) is regarded as a risk factor for acquiring TB infection. In this prospective study among long-term travellers we examined the incidence of TB infection using Interferon gamma release assay (IGRA) test and compared these data with results from a visit to the TB department to which all long-term travellers were routinely referred.
  
  
  METHODS
  Immunocompetent adults, travelling for 13-52 weeks to TB-endemic countries, donated blood pre- and post-travel for IGRA. The pre-travel IGRA was only tested in case of a positive IGRA post-travel. Results from their visit(s) to the TB department for TST pre- and post-travel were collected and compared with study results.
  
  
  RESULTS
  We found two IGRA conversions in a group of 516 travellers, resulting in an attack rate (AR) of 0.4% (95% CI: 0.5 - 13.9) and an incidence rate (IR) of 0.85 per 1000 person-months (95% CI: 0.1-3.1).We found 5 tuberculin skin test (TST) conversions, resulting in AR of 1.9% (5/261; 95% CI: 0.6 - 4.4) and an IR of 4.26 per 1000 person-months (95% CI: 1.38- 9.94). In our study these converters all had a negative IGRA. One traveller however, who was retested later at the TB department due to a positive TST, then appeared to have seroconverted.
  
  
  CONCLUSIONS
  The risk of long-term travellers among our study population acquiring TB infection is low. We conclude that post-travel IGRA alone could be used for screening for TB infection among long-term travellers to high-endemic TB countries, but preferably not earlier than 8 weeks after return. One might even argue that IGRA testing should be limited to only those travellers who are going to work in a medical setting. A person with a positive IGRA should be referred to a TB physician for further evaluation.
authors.forename: Floor
authors.initials: F
authors.lastname: Elfrink
authors.forename: Anneke
authors.initials: A
authors.lastname: van den Hoek
authors.forename: Marlies E
authors.initials: ME
authors.lastname: Mensen
authors.affiliation: Department of Infectious Diseases, Public Health Service (GGD), Nieuwe Achtergracht 100, 1018 WT Amsterdam, the Netherlands. gsonder@ggd.amsterdam.nl.
authors.forename: Gerard J B
authors.initials: GJ
authors.lastname: Sonder
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology*; D059425:Interferon-gamma Release Tests; D008297:Male; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011446:Prospective Studies; D014195:Travel; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology; D055815:Young Adult
chemical_list: D007371:Interferon-gamma