Cost-effectiveness Analysis of Community-based Latent Tuberculosis Infection Screening Strategy in Changhua

• Main Authors: Yi-Ju Chen, 陳怡如
• Other Authors: Wei-Chu Chie
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/38guq7

碩士 === 國立臺灣大學 === 流行病學與預防醫學研究所 === 107 === Background In contrast to the countries with low incidence of tuberculosis (TB), strategies of controlling Tuberculosis (TB) in those countries with moderate disease burden, the adoption of WHO guideline through passive case finding and chemoprevention for latent tuberculosis infection (LTBI) through active investigation for contact tracing is not sufficient to reach the goal of disease prevention. The alternative is the use of screening as a secondary prevention with the conventional Tuberculin Skin Test (TST) and the recently proposed Interferon-gamma Release Assay (IGRA) aimed at early detection and treatment of TB arising from among LTBI in average-risk population followed by the provision of chemoprophylaxis to decrease the risk of further progression to clinical TB. Given the costs incurred in screening earlier and the effectiveness of averting TB cases accrued later, economic evaluation plays an important role in decision-making for such kinds of screening strategy, which been barely addressed. Aims This thesis aimed at assessing the efficacy and cost-effectiveness of applying Tuberculin Skin Test (TST), IGRA, and the combination of the two compared with no screen together with the consideration of current context of TB prevention strategy in Changhua. Material and Methods The forces of natural evolution of tuberculosis from susceptible, LTBI, reinfection, clinical TB resulting from exogenous and endogenous sources, to TB death was first derived from the empirical data of TB surveillance registry, contact investigation registry, and community-based screening samples with the consideration of the effect of age, sex. The diagnostic characteristics of TST, IGRA, and the combination of the two were derived by using the data from Changhua integrated community-based screening. Based on the parameters of TB evolution, the effectiveness and cost-effectiveness for the four scenarios of no screen, TST screening, IGRA screening, and screening by using TST combined with IGRA were assessed by using Markov decision tree under the context of TB prevention in Changhua. The incremental cost-effectiveness ratios (ICERs) with deterministic and probabilistic approach were estimated. Results The incidence of TB in 2016 was 50 per 100,000. Regarding the force of TB infection rate and conversion rate, subjects with positive IGRA had higher risks on both rates. Male also had higher risk in these two rates. While the elderly had a higher risk for the progression to clinical TB from LTBI, the risk of LTBI was higher for the young. The case-fatality rate of TB in Changhua was around 20%. By using the parameters derived from the empirical data in Changhua, the cost-effectiveness of the population-based screening strategies using TST and IGRA were assessed. The combination uses of TST and IGRA provides a higher efficacy in averting TB cases compared with no screen. Regarding the cost-effectiveness of TB case averted, the ICER for prevention one TB case was estimated as NT 35,966, NT 40,973, NT 45,748, and NT 34,404 for the screening strategy using TST, IGRA, the combination of the two in parallel and that in serial, respectively with the probability of being cost effective of 85.0%, 78.5%, 77.0%, and 86.0%, respectively, based on the NT 60,000 threshold value of wiliness-to-pay. The ICER for life-years gain was NT 39,439, NT 44,284, NT 55,086, and NT 37,190 for TST screen, IGRA screen, the screen with the combination of TST and IGRA in parallel, and that in serial, respectively. The NT 60,000 willing-to-pay threshold gives the probability of being cost-effective around 60% for the four strategies compared with no screen. Conclusion The strategy of screening for LTBI in an average-risk population by using TST, IGRA and TST combined IGRA is effective in averting TB cases through the early identification of LTBI subjects followed by the chemoprophylaxis of INH. Keywords: population-based screen, LTBI, TST, IGRA (QFT-GIT), cost-effectiveness analysis