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Table 2 Model assumptions

From: Tuberculosis screening of travelers to higher-incidence countries: A cost-effectiveness analysis

  Base value Range Sources
Annual risk of progression from latent tuberculosis (LTBI) to TB disease    
   Among persons newly infected during travel    
First two years after infection 0.025 0.02 – 0.05 [33]
Subsequently 0.001 0.001 – 0.002 [34]
   Among persons with LTBI before travel, given    
No underlying radiographic abnormalities [see below] 0.001   [34]
Underlying radiographic abnormalities [see below] 0.0066   [34]
   Reduction in risk afforded by:    
Full 9 months of isoniazid, given drug-sensitive latent infection 90%   [35]
<6 months isoniazid 0%   [36]
Previous LTBI, among persons who are reinfected during travel 79%   [37]
Prevalence of isoniazid resistance    
   Mexico 0.072 0.072 – 0.12 [38, 39]
   Dominican Republic 0.198 -- [40]
   Haiti 0.159 -- [41]
Active TB    
   Proportion of travelers with active TB symptomatic upon return 0.27 0.11 – 0.44 [21, 26]
   Probability of hospitalization given active TB diagnosed after symptoms 0.8   [42]
   Probability of hospitalization given active TB diagnosed through screening 0.5   [21, 22]
   Probability of completing full anti-TB therapy 1.0   assumed
   Risk of major side effect with full anti-TB therapy 0.051 0.01 – 0.1 [43]
   Probability of death, given major treatment side effect 0.015 0.001 – 0.032 [43–45]
Treatment of latent TB infection    
   Probability of completing 9 months isoniazid 0.647 0.62 – 1 [10, 46]
   Probability of major side effect with isoniazid 0.003   [43–45]
   Probability of death, given major treatment side effect 0.015 0.001 – 0.032 [43–45]
Tuberculin skin testing    
   Probability of boosting, given previous BCG vaccination 0.25   [17]
   Specificity for LTBI 0.875 - [17]
   Sensitivity for LTBI 0.99 - [47, 48]
   Sensitivity for active TB 0.88 - [48]
   Probability of loss to follow-up between pre- and post- travel evaluations, for repeat testing strategies 0.34   [7]
Probability of abnormal chest X-ray upon return from travel    
   With preexisting LTBI 0.11 0.07 – 0.15 [33, 34, 49, 50]
   With LTBI newly acquired during travel 0   assumed
   With active TB 0.95 0.9 – 1 [51, 52]
Sputum cultures (3) for M. Tuberculosis    
   Specificity 0.99   [51]
   Sensitivity 0.9   [53]
Costs for TB screening and care in the US (expressed in 2005 US dollars)    
   Initial clinic visit $68   [54, 25]
   Tuberculin skin test $12   [42, 23]
   Follow-up clinic visit after tuberculin test $36   [42]
   Chest radiograph with reading $36   [42]
   Isoniazid, 9 months supply $25   [54]
   7 outpatient clinic visits during isoniazid treatment $385   [54]
   Major adverse reaction to isoniazid $9,834   [54]
   3 sputa for AFB smear and culture, after abnormal CXR $126   [55, 56]
   Inpatient treatment of active TB disease $9,061   [57]
   Outpatient treatment of active TB disease $2,600   [42]
   Contact investigation and management, per active TB case (identified via screening) $4,483   [42, 24]