Cost-effectiveness of interferon-gamma release assay for systematic tuberculosis screening of healthcare workers in low-incidence countries

Abstract

Tuberculosis (TB) is one of the important occupationally acquired infectious diseases in low-incidence countries. Delays in TB diagnosis and treatment among healthcare workers (HCWs) result in costly large-scale TB contact screening among patients and other HCWs. To assess the cost-effectiveness of TB screening for HCWs using interferon-gamma release assays (IGRAs) compared with tuberculin skin test (TST) and chest x ray (CXR). Markov models were constructed using a hospital payer perspective. The target populations were a hypothetical cohort of 30-year-old HCWs at the time of employment, and a hypothetical cohort of HCWs working on a high-risk ward until 60 years of age. Six strategies were modelled: TST, QuantiFERON-TB Gold In-Tube (QFT), T-SPOT.TB (T-SPOT), TST followed by QFT, TST followed by T-SPOT, and CXR. The main outcome measure of effectiveness was quality-adjusted life-years (QALYs). Costs and QALYs gained per person screened were calculated. QFT was the most cost-effective strategy at the 'willingness to pay' level of US$ 50,000/QALYs gained (at the time of employment: US$ 334.91, 21.071 QALYs; on a high-risk ward: US$ 1050.32, 20.968 QALYs; values for 2012). Cost-effectiveness was sensitive to latent TB infection (LTBI) rate and bacillus Calmette-Guérin vaccination rate. TST followed by QFT was more cost-effective than QFT when the LTBI rate was <0.026 at the time of employment and <0.08 on a high-risk ward. Systematic TB screening using QFT is cost-effective for screening HCWs, and is recommended in low-incidence countries.