Table 1. Formula and examples of method for estimating prevalence of latent TB infection, United States, 2011–2015* .

Variable	a	b	c	d	e	f	g	h
Jurisdiction	Population	Average annual no. active TB cases	Proportion of TB cases attributed to recent transmission	Annual no. cases attributed to reactivation TB	Estimated no. infected residents if 0.10% annual risk for progression	Estimated prevalence of infection if 0.10% annual risk for progression, %	Sensitivity analysis for estimated prevalence of latent infection, %
							Lower uncertainty limit based on 0.14% annual risk for progression	Upper uncertainty limit based on 0.06% annual risk for progression
Example X	Any size	0	NA	0	NA	<1	NA	NA
Example Y	150,000	1	0	1	1,000	0.7	0.5	1.1
Example Z	2,000,000	50	0.2	40	40,000	2.0	1.4	3.3

*Let a = jurisdiction population, b = average annual no. TB cases in that jurisdiction, and c = proportion of TB cases attributed to recent transmission (i.e., [1 – c] = proportion attributed to latent TB infection). Then if b = 0, d = 0, and f <1%, otherwise d = b × (1 – c) and e = d/0.0010 if one assumes a 0.10% annual risk and f = e/a (×100 to express as a percentage) or (d/0.0014/a for lower uncertainty limit and h = d/0.0006/a for upper uncertainty limit. NA, not applicable; TB, tuberculosis.