Abstract
Introduction: Tuberculosis (TB) is a communicable disease caused by M. tuberculosis. Contacts of TB cases become clinically active TB or remain in the latent tuberculosis infection (LTBI), which is subsequent progression to tuberculosis disease. Currently, the available tests for LTBI diagnosis include tuberculin skin test (TST) and interferon-gamma release assay (IGRA). In Thailand, IGRA test is costly and has not been included in the benefit package. The results from this study can be used as an evidence informed policy whether IGRA test should be included in the benefit package and can be applied to support the strategies to eradicate TB. Objectives: To evaluate cost-utility analysis, budget impact analysis and feasibility analysis of LTBI diagnosis for contacts of TB patients using societal and government perspectives. Methodology: Cost-utility analysis using a decision tree and Markov model was performed to simulate the costs and utilities, and to estimate the budget impact of contacts with pulmonary TB patients. All parameters were obtained from published studies. Lifetime horizon was applied with both costs and outcomes discounted by 3%, as recommended by the guidelines of economic evaluation in Thailand. One way and probabilistic sensitivity analyses were conducted to examine the uncertainty of input parameters. This study considered three alternative diagnosis strategies as follows: 1) No screening, 2) TST alone to diagnose LTBI, if TST test was positive, treatment would be provided, and 3) IGRA alone to diagnose LTBI, if IGRA test was positive, treatment would be provided. Focus group discussion and literature reviews were applied for feasibility analysis. Results: The incremental cost-effectiveness ratios (ICER) of IGRA alone compared with TST alone was THB 1,220,287 per QALY gained. At the willingness to pay (WTP) THB 160,000 per QALY gained, IGRA would not be cost-effective. If the price of IGRA was decreased to THB 575 per test, the strategy of IGRA would be cost-effective. Five-year budget for TST and IGRA was estimated to be THB 148 million and THB 330 million, respectively. The barriers for IGRA implementation were lack of laboratory infrastructure and limited availability of laboratory personnel.
