Authors: G Orlando S Merli L Cordier F Mazza G Casazza A M Villa L Codecasa E Negri A Cargnel M Ferrarese G Rizzardini
Publish Date: 2010/04/22
Volume: 38, Issue: 3, Pages: 195-204
Abstract
Recent immigrants from developing countries 2 years since immigration are at very high risk of active TB disease due to reactivation of latent infections acquired in the country of origin In industrialized lowincidence TB countries targeted testing programs for high risk groups could allow the detection of latently infected persons who would likely benefit from a course of preventive treatment In this study we evaluated the tuberculin skin test TST and interferonγ enzymelinked immunosorbent assay QuantiFERON TBgold in tube QFTIT strategies for TB infection screening programs in recent immigrants from highly endemic countriesThis is a prospective crosssectional study Paired tests performed in 1130 immigrants attending an outpatient ward between 2005 and 2007 for any health problem were evaluated by intentiontotreat ITT and perprotocol PP analysis for efficiency and efficacy of screening programPositive TST and QFTIT were observed in 3604 versus 2982 ITT and in 4527 versus 3022 PP respectively A higher dropout rate was observed for TST 2035 vs 133 p 00001 Second level assessment was accepted by half of the TST positive patients Overall agreement rate between 887 paired tests was fair k = 038 Higher k values were observed for higher TB prevalence rate in the country of origin k = 043 for TST induration diameters 20 mM k = 047 in subjects aged 40–50 years k = 041 and in unvaccinated persons k = 040 In a multiple logistic regression model continent of origin class of TB prevalence in the country of origin and contacts with TB patients were found to be significantly associated with the probability of TST and QFTIT positive result Low education levels were associated only to an increased risk of TST positive resultsThe drawback of the TST screening strategy in recent immigrants from highly endemic countries is due to low sensitivity/specificity of the test and to high dropout rate with an overall significant lowering in strategy efficacy/efficiency The higher QFTIT specificity prevents unnecessary overload of the health care system and although more expensive might represent a costeffective alternative to TST in targeted screening programs directed to high risk populations
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