Cost-effectiveness of the NICE guidelines for screening for latent tuberculosis infection: the QuantiFERON-TB Gold IGRA alone is more cost-effective for immigrants from high burden countries

Abstract

NICE (National Institute for Health and Clinical Excellence) guidelines for new entrant tuberculosis (TB) screening recommend chest x ray (CXR) for immigrants from countries with TB incidence >40/10⁵, and tuberculin skin test (TST) for people with normal CXR from very high TB prevalence countries. A revised screening policy using first-line QuantiFERON-TB Gold (QFT) in high risk immigrants was piloted in 2007. Initially, TST was offered to immigrants from countries with TB incidence 200–339/10⁵, and QFT to those from countries with incidence >340/10⁵. When increased resources became available, all immigrants from countries with TB incidence >200/10⁵ had QFT. Those with positive QFT were invited for CXR. 1336 immigrant were invited for screening, with a 32% attendance rate. 280 patients had QFT, of which 38% were positive, with <2% being indeterminate. Using the NICE approach, the cost of screening these 280 immigrants would be £13 346.75 (£47.67 per immigrant) and would identify 83 cases of latent TB infection (LTBI). Using first-line QFT followed by CXR the cost was £9781.82 (£34.94 per immigrant) and identified 105 cases of LTBI. The cost to identify one case of LTBI following NICE guidelines would be £160.81 and using the present protocol was £93.16. For immigrants from high risk countries QFT blood testing followed by CXR is feasible for TB screening, cheaper than screening using the NICE guideline and identifies more cases of LTBI.