. Author manuscript; available in PMC: 2017 Oct 27.

Published in final edited form as: Lancet Public Health. 2017 Jul;2(7):e323–e330. doi: 10.1016/S2468-2667(17)30119-6

Table 1.

Five Scenarios under which simulations were run

Scenario	Brief Description	Comments
Baseline	Demographic changes only	Constant rate of LTBI reactivation beyond five years after infection, no change in TB dynamics in 1980s – 1990s
Declining Progression	Allows declining rate of LTBI reactivation	As in Baseline, but allows for linear decline in the rate of LTBI reactivation with time since infection
1980s Increase	Increased TB incidence from 1984 to 1992	As in Declining Progression, but allows for higher rates of transmission and reactivation as observed from 1984 to 1992, without specifying a specific mechanism (e.g., HIV or worsening TB control infrastructure)
Differential Progression	Different reactivation rates in US-born versus foreign-born	As in 1980s Increase, but allows for different rates of progression from LTBI to active TB in US-born and foreign born individuals, as well as allowing the rate of progression in foreign-born individuals with LTBI to decline by 1·5 to 5·25% per year after 2007, without specifying a specific mechanism (e.g., due to improved nutritional/immune status).^*
Reduced Importation	Reduced importation of subclinical TB from 2007 to 2012	As in the 1980s Increase scenario, but models a decrease in imported subclinical TB without specifying a specific mechanism (e.g. changing patterns of immigration or use of TB culture rather than sputum smear microscopy to screen some foreign-born persons seeking permanent residence in the US prior to entry¹⁷). We represent this decrease as a linear reduction in the risk of incident active TB among immigrants in their first year after arrival; we assume that in 2007 immigrants have a normal risk, but by 2012 (and after) have that first-year risk cut in half.

Rates of decline were selected based on preliminary simulations. Our primary analysis of this scenario assumed that LTBI progression rates among the foreign-born continued to decline through 2025. As it is not clear that such a decline would continue year after year, we conducted a secondary analysis which assumed LTBI progression rates did not decline further after 2015. Further details are provided in the Supplement.