Volume 24, Number 10—October 2018
Dispatch
Simple Estimates for Local Prevalence of Latent Tuberculosis Infection, United States, 2011–2015
Maryam B. Haddad
, Kala M. Raz, Timothy L. Lash, Andrew N. Hill, J. Steve Kammerer, Carla A. Winston, Kenneth G. Castro, Neel R. Gandhi, and Thomas R. Navin
, Kala M. Raz, Timothy L. Lash, Andrew N. Hill, J. Steve Kammerer, Carla A. Winston, Kenneth G. Castro, Neel R. Gandhi, and Thomas R. Navin
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.
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