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BACKGROUND: UK tuberculosis (TB) notifications are rising due to disease in the immigrant population. National screening guidelines have been revised but cost-effectiveness analyses are hampered by the lack of data on the comparative performance of tuberculin skin tests (TSTs) and interferon ?? release assays (IGRAs) in immigrants. METHODS: Three-way evaluation of TSTs and two IGRAs (QuantiFERON Gold in-tube (QFN-GIT) and T-SPOT.TB) in immigrants aged ???16 years to quantify test positivity, concordance and factors associated with positivity. Yields were computed at different incidence thresholds and the relative cost-effectiveness of screening was estimated using different latent TB infection (LTBI) screening modalities at varying incidence thresholds with or without port-of-arrival chest x-ray (CXR). RESULTS: 231 immigrants were included; median age 29 (IQR 24-37). TSTs were accepted by 80.9%, read in 93.5% and 30.3% were positive - QFN-GIT and T-SPOT.TB positive in 16.6% and 22.5% respectively. Positive TSTs, QFN-GIT and T-SPOT.TB were independently associated with increasing TB incidence in immigrants' countries of origin (p=0.007, 0.007, 0.037 respectively). Implementing current guidance (threshold 40/100???000 per year) would identify 98-100% of LTBIs (depending on test) but entail testing 97-99% of the cohort; screening at 150/100???000 per year would identify 49-71% of LTBIs but only entail screening half the cohort. The two most cost-effective screening strategies were no port-of-entry chest radiography and screen with single-step QFN-GIT at 250/100???000 per year (incremental cost-effectiveness ratio (ICER)) ??21???565.3/case averted); and no port-of-entry CXR and screen with single-step QFN-GIT at 150/100???000 per year (averted additional 7.8 TB cases; ICER ??31???867.1/case averted). CONCLUSIONS: UK immigrant screening could cost-effectively and safely eliminate mandatory CXR on arrival by emphasising systematic screening for LTBI with single-step IGRA. Intermediate incidence thresholds balance the need to identify as many imported LTBIs as possible against limited service capacity.


Enlarged microscopic image of TB-causing bacteria, Mycobacterium tuberculosisWhen I immigrated to the UK as a student, I had to do something that I wasn't expecting. I had to carry with me a recent chest X-ray. I thought this was completely unnecessary. Why...