Cost-optimisation of screening for latent tuberculosis in close contacts

The aim of the present study was to perform cost-minimisation analysis of contact investigation from a public health perspective using the tuberculin skin test (TST) and a new blood assay, QuantiFERON-TB Gold (QFT-G). A decision-analysis model simulated the costs of investigating a cohort of adult close tuberculosis contacts by the public health service following the current German guidelines over a period of 2 yrs. The economic outcomes were compared with alternative screening strategies. These were: 1) QFT-G instead of TST; 2) TST followed by QFT-G; and 3) TST followed by QFT-G in vaccinated (bacille Calmette-Guerin (BCG)) subjects. In a base-case analysis, the costs of TST-based screening were 91.06 Euros (EUR)(.)contact(-1), assuming a 1% tuberculosis-case-finding incidence. The least expensive strategy was TST screening plus subsequent QFT-G testing (52.05 EUR), resulting in a 43% cost reduction. Using QFT-G alone in BCG-vaccinated subjects who tested positive in the TST led to a 39% cost reduction. The savings using QFT-G alone instead of TST amounted to 29.77 EUR(.)contact(-1). The results depended on the acquisition costs assumed and the proportion of positive results in TST-based screening. Screening for tuberculosis by combining tuberculin skin testing and QuantiFERON-TB Gold markedly reduces public health costs compared with tuberculin skin test screening alone.