Priorities for screening and treatment of latent tuberculosis infection in the United States

Abstract

Rationale: To improve the effectiveness of tuberculosis (TB) control programs in the United States by identifying cost-effective priorities for screening for latent tuberculosis infection (LTBI).

Objectives: To estimate the cost-effectiveness of LTBI screening using the tuberculin skin test (TST)and interferon-g release assays (IGRAs).

Methods: A Markov model of screening for LTBI with TST and IGRA in risk-groups considered in current LTBI screening guidelines.

Measurements and main results: In all risk-groups, TST and IGRA screening resulted in increased mean life expectancy, ranging from 0.03–0.24 life-months per person screened. IGRA screening resulted in greater life expectancy gains than TST. Screening always cost more than not screening, but IGRA was cost-saving compared with TST in some groups. Four patterns of cost-effectiveness emerged, related to four risk categories. (1) Individuals at highest risk of TB reactivation (close contacts and those infected with HIV): the incremental cost-effectiveness ratio (ICER) of IGRA compared with TST was less than $100,000 per quality-adjusted life year (QALY) gained. (2) The foreign-born: IGRA was cost-saving compared with TST and cost-effective compared with no screening (ICER ,$100,000 per QALY gained). (3) Vulnerable populations (e.g., homeless, drug user, or former prisoner): the ICER of TST screening was approximately $100,000–$150,000 per QALY gained, but IGRA was not cost-effective. (4) Medical comorbidities (e.g., diabetes): the ICER of screening with TST or IGRA was greater than $100,000 per QALY.

Conclusions: LTBI screening guidelines could make progress toward TB elimination by prioritizing screening for close contacts, those infected with HIV, and the foreign-born regardless of time living in the United States. For these groups, IGRA screening was more cost-effective than TST screening.

Figure 1.

Number of cases of active tuberculosis (TB) preventable through latent tuberculosis infection (LTBI) screening in each risk-group considered by current United States LTBI screening guidelines. The bar graph depicts the absolute number of cases of active TB that could be prevented through screening all members of a given risk-group currently living in the United States. The Y-axis is denominated in terms of the absolute number of cases of active TB that could be prevented through screening with either interferon-γ release assays (IGRA) (for risk-groups in which the incremental cost-effectiveness ratio [ICER] of IGRA screening is <$100,000 per quality-adjusted life-year [QALY] gained), or tuberculin skin test (TST) (for risk-groups in which the ICER of TST is <$100,000 per QALY gained). The number of cases preventable was calculated using estimates of the number of individuals in each risk-group living in the United States at the start of the analysis (N), and model-based estimates of the number needed to screen to prevent one case of active TB (NNS). We defined total preventable cases as N/NNS. Black bars illustrate risk-groups in which the ICER of screening with either IGRA or TST is less than $100,000 per QALY gained, but for whom screening is not currently recommended. The shaded bars illustrate risk-groups in which the ICER of screening with either TST or IGRA is less than $100,000 per QALY gained and for whom screening currently is recommended. The white bars indicate risk-groups in which the ICER of both IGRA and TST screening are greater than $100,000 per QALY gained, but for whom screening currently is recommended.

Figure 2.

Two-way sensitivity analysis of the incremental cost-effectiveness ratio of screening for latent tuberculosis infection (LTBI) using tuberculin skin test (TST) or interferon-γ release assays (IGRA) in foreign-born residents living in the United States more than 5 years, age 25–44 years. The figure illustrates the choice of screening strategy assuming a willingness to pay $100,000 per quality-adjusted life-year gained. The vertical axis depicts IGRA test specificity and the horizontal axis TST test specificity. The solid lines define the boundaries between combinations of IGRA and TST test specificity that result in either IGRA, TST, or no screening having an incremental cost-effectiveness ratio less than $100,000 per quality-adjusted life-year gained. The asterisk represents the test characteristics assumed in the base case scenario.