Cost-effectiveness of Interferon Gamma Release Assay (QFT-IT) as a Diagnostic Test for Intraocular Tuberculosis

Abstract

Background:Interferon Gamma Release Assays (IGRAs) have proven to be potential replacement of tuberculin skin test (TST) in screening and diagnosing tuberculosis as shown by previous health economic studies. Given that these studies all center on pulmonary tuberculosis, we sought to examine the cost-effectiveness of IGRAs, specifically QFT-IT, as a diagnostic test for intraocular tuberculosis among uveitis patients in Singapore. Method: A decision tree was constructed to evaluate the cost-effectiveness of the QFT-IT for diagnosing intraocular tuberculosis among uveitis patients over a 30-year horizon. The input data were based on a cohort of 102 patients who presented with symptoms of uveitis and underwent relevant treatment and follow-up visits from 2009 to 2010 at Singapore National Eye Center (SNEC). By calculating their incremental cost-effectiveness ratio, we compared the cost-effectiveness of three strategies: TST alone, QFT-IT alone and TST followed by QFT-IT as a confirmatory test. Results:Our results show that in cost terms alone, QFT-IT alone strategy is the most expensive one (889 SGD per person), followed by TST alone (850 SGD per person) and finally the dual strategy (789 SGD per person). While examining effectiveness alone, TST alone strategy is the most effective one that helps gain 17.4923 quality-adjusted life years (QALYs) followed by QFT-IT alone and the dual strategy. Using the conventional willingness to pay of 50,000 USD/QALY (63000 SGD/QALY), having an incremental cost-effectiveness ratio of 1644 SGD/QALY demonstrates that TST alone strategy is the best choice to screen ocular TB in Singapore. Conclusion: Given the local ocular tuberculosis prevalence and key assumptions made in the analysis model, the TST alone strategy is recommended to diagnose intraocular TB among uveitis patients in Singapore.