Screening travellers to high-endemic countries for infection with Mycobacterium tuberculosis using interferon gamma release assay; a prospective study

Abstract

BackgroundInternational 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.MethodsImmunocompetent 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.ResultsWe 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2334-14-515) contains supplementary material, which is available to authorized users.

The global prevalence of latent tuberculosis: a systematic review and meta-analysis

“…Among the included studies, 36 used one or more variants of the QFT assay, including individuals sampled with QFT Gold (n=8262) [29,36,48,58,59,70,78,83,94], QFT-GIT (n=56 327) [13, 28, 39, 42, 45, 49, 51, 57, 60, 67, 71, 72, 79-81, 83, 86-88, 93, 96, 104-107, 110, 113] and a single study using QFT-Plus (n=829) [89]. Seven studies used T-SPOT.TB (n=5547) [31,62,65,72,90,104,114] and two of these included simultaneous QFT-GIT [72,104].…”

“…Seven studies used T-SPOT.TB (n=5547) [31,62,65,72,90,104,114] and two of these included simultaneous QFT-GIT [72,104]. In total, 41 studies used one or more IGRA tools (n=67 167 individuals) [13, 28, 29, 31, 36, [13,31,36,42,45,49,51,65,72,80,83,86,87,93,96,[104][105][106][107]113]. The pooled sample sizes of studies using TST were larger than studies using IGRA in all intervals and largest in the high-incidence interval (table 1).…”

Tuberculosis infection in children visiting friends and relatives in countries with high incidence of tuberculosis

“…Since state-level data are those usually published in official reports and regional incidence could vary significantly within the same country, a limitation of the study is the unavailability of data on regional incidence, which may hinder the assessment on the intensity of exposure to M tuberculosis . [ 17 ] In addition, due to the specific immigration patterns of Catalonia, some countries of origin will be overrepresented in our sample.…”

“…[ 13 ] The recent increase in international travel of immigrants to their countries of origin to visit friends and relatives (VFR) [ 14 – 16 ] and subsequent exposure to M tuberculosis in countries with incidences of TB higher than in the host countries could partially explain the differences in incidence between children of immigrant families and children from the autochthonous population. [ 17 ] It seems plausible to associate travel-related factors with risk of contagion, including the intensity of transmission (proportional to the local TB incidence), the relationship and contact with the local population, the duration of the stay, and individual host factors. [ 18 ]…”

Determinación del interferón-gamma en tuberculosis: Principios básicos y utilidad

“…Muchos autores han sugerido implementar la prueba IGRA con fines de detección de ITBL en viajeros a países altamente endémicos de TB quienes retornan 8 semanas después a su país de origen, principalmente cuando existe la sospecha de una potencial exposición al haber estado involucrados en actividades propias del sector salud. [36][37][38]40 Prácticamente todas las guías internacionales que emiten recomendaciones de efectuar pruebas de cribado en inmigrantes incorporan el uso del IGRA. 14 Resulta primordial implementar el poder pronóstico del IGRA mediante la reducción del número necesario a tratar, lo cual constituye una prioridad de investigación urgente.…”