Different screening strategies (single or dual) for the diagnosis of suspected latent tuberculosis: a cost effectiveness analysis

Abstract

BackgroundPrevious health economic studies recommend either a dual screening strategy [tuberculin skin test (TST) followed by interferon-γ-release assay (IGRA)] or a single one [IGRA only] for latent tuberculosis infection (LTBI), the former largely based on claims that it is more cost-effective. We sought to examine that conclusion through the use of a model that accounts for the additional costs of adverse drug reactions and directly compares two commercially available versions of the IGRA: the Quantiferon-TB-Gold-In-Tube (QFT-GIT) and T-SPOT.TB.MethodsA LTBI screening model directed at screening contacts was used to perform a cost-effectiveness analysis, from a UK healthcare perspective, taking into account the risk of isoniazid-related hepatotoxicity and post-exposure TB (2 years post contact) using the TST, QFT-GIT and T-SPOT.TB IGRAs.ResultsExamining costs alone, the TST/IGRA dual screening strategies (TST/T-SPOT.TB and TST/QFT-GIT; £162,387 and £157,048 per 1000 contacts, respectively) cost less than their single strategy counterparts (T-SPOT.TB and QFT-GIT; £203,983 and £202,921 per 1000 contacts) which have higher IGRA test costs and greater numbers of persons undergoing LTBI treatment. However, IGRA alone strategies direct healthcare interventions and costs more accurately to those that are truly infected.Subsequently, less contacts need to be treated to prevent an active case of TB (T-SPOT.TB and QFT-GIT; 61.7 and 69.7 contacts) in IGRA alone strategies. IGRA single strategies also prevent more cases of post-exposure TB. However, this greater effectiveness does not outweigh the lower incremental costs associated with the dual strategies. Consequently, when these costs are combined with effectiveness, the IGRA dual strategies are more cost-effective than their single strategy counterparts. Comparing between the IGRAs, T-SPOT.TB-based strategies (single and dual; £39,712 and £37,206 per active TB case prevented, respectively) were more cost-effective than the QFT-GIT-based strategies (single and dual; £42,051 and £37,699 per active TB case prevented, respectively). Using the TST alone was the least cost-effective (£47,840 per active TB case prevented). Cost effectiveness values were sensitive to changes in LTBI prevalence, IGRA test sensitivities/specificities and IGRA test costs.ConclusionA dual strategy is more cost effective than a single strategy but this conclusion is sensitive to screening test assumptions and LTBI prevalence.

South African recommendations for the management of rheumatoid arthritis: An algorithm for the standard of care in 2013

“…In low-prevalence settings, the combination of TST and IGRA may be the best strategy. [51] Currently, there is little consensus on the most appropriate screening test in high-prevalence settings such as SA. [52] A patient due to commence biologic therapy should have a TST, an IGRA test (if deemed appropriate by the clinician), and a CXR.…”

Laboratory Diagnosis of Latent and Active Tuberculosis Infections in Trinidad & Tobago and Determination of Drug Susceptibility Profile of Tuberculosis Isolates in the Caribbean

“…In terms of cost, however, the TST appears best suited for the resource-strapped environment of Trinidad & Tobago (if the calculation of this variable is based mainly on the cost of the materials required to perform the test versus the cost of labor and other inputs). This argument is partly supported by Pooran et al, who concluded in a recent report that screening for LTBI using TST alone was the most cost-effective testing strategy but ultimately incurred the highest cost due to test inaccuracies [25]. Another factor that may make the TST less cost-effective over time is high replacement costs, since the Mantoux test solution is often not accessible in developing countries and would have to be replaced with the relatively labor-intensive IFN-release assay.…”

Multicytokine Detection Improves Latent Tuberculosis Diagnosis in Health Care Workers

“…The combination of the TST and the QFT test could be an alternative way of improving diagnostic testing for LTBI (1,9,18,25). However, the TST itself has a poor sensitivity of 80% (17) and poor specificity among individuals vaccinated with BCG, which is the case for most HCW exposed to TB.…”