Prevalence of latent tuberculosis infection among foreign students in Lübeck, Germany tested with QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold Plus

Abstract

Background: The tuberculosis (TB) incidence rate in foreign-born individuals has been increasing in Germany in recent years. Foreign students may be an important source of latent tuberculosis infection (LTBI) in low-incidence countries. In Germany, there are no guidelines for LTBI screening of foreign students. The aim of the study was to estimate LTBI prevalence and evaluate associated risk factors among foreign students in Germany. The second purpose of our study was to compare the results of the new generation of QuantiFERON-TB Gold Plus (QFT-Plus) to those of its predecessor QuantiFERON-TB Gold In-Tube (QFT-GIT).

Methods: This cross-sectional study was conducted between February 2016 and March 2016. Foreign students and young professionals attending the university and higher education institutes in Lübeck, Germany were tested with QFT-Plus and QFT-GIT. Participants filled out a questionnaire for the purpose of LTBI risk assessment and analysis. Variables associated with a positive test result were analyzed using logistic regression.

Results: One hundred thirty four students participated in the study. The overall prevalence as regards positive results from both tests, QFT-Plus and QFT-GIT, was 9.7%, and the prevalence of positive QFT-Plus results was 8.2%. The main independent variables associated with a positive QFT-Plus result were a) being born in a high-incidence country (OR = 6.7, 95% CI: 1.3-34.3) and b) previous contact with a person with active TB (OR = 4.5, 95% CI: 1.1-18.3). Higher age (OR = 2.8, 95% CI: 0.7-11.3) and male gender (OR = 1.6, 95% CI: 0.4-6.7) showed a tendency toward positive QFT-Plus results but this was not statistically significant. Agreement between QFT-Plus and QFT-GIT results was κ = 0.85, p < 0.001.

Conclusions: The LTBI prevalence among foreign students was about 10%. We recommend implementing a policy whereby all foreign students are screened by means of a questionnaire about LTBI risk factors, so that only students with present risk factors are tested for LTBI. The agreement between the new QFT-Plus and the QFT-GIT (κ = 0.85) was good. QFT-Plus might be used in the same format as its predecessor.

Keywords: Foreign students; Latent tuberculosis infection; QuantiFERON-TB Gold Plus; Risk factors.

Fig. 1

Variables associated with positive QFT-Plus. The variables were analyzed using logistic regression models to identify independent variables associated with a positive QFT-Plus result. * Countries with an annual TB incidence of ≥125:100,000

Fig. 2

Concordance between QFT-Plus and QFT-GIT. For QFT-Plus the highest IFN-γ value of antigen tubes TB-1 and TB-2 was taken as the result