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Table 1 Model parameters and assumptions for analysis comparing two programs for treating LTBI in U.S.-bound refugees

From: A cost-benefit analysis of a proposed overseas refugee latent tuberculosis infection screening and treatment program

Parameter

Value

Source

Epidemiological Parameters

  

Age at screening

30

Assumption

Prevalence of active TB in refugee camps (Per 100,000)

  

 High Prevalence

955

[28]

 Moderate Prevalence

426

[28]

 Low Prevalence

9

[28]

TST sensitivity

89 %

[32]

TST specificity

  

 Non BCG vaccinated populations

98 %

[34]

 BCG vaccinated during infancy only

92 %

[34]

 BCG vaccinated after infancy

60 %

[34]

 Overall TST specificitya

85 %

calculated

Proportion with positive TST

  

 High Prevalence

55 %

[2427]

 Moderate Prevalence

35 %

[2427]

 Low Prevalence

20 %

[2427]

True prevalence of LTBIb

  

High Prevalence

54 %

calculated

Moderate Prevalence

27 %

calculated

Low Prevalence

7 %

calculated

Probability of abnormal chest radiograph with active disease

100 %

[33]

Probability of abnormal chest radiograph with LTBI (inactive TB)

11 %

[33]

Specificity of chest radiograph with no infection

95 %

[35]

Probability of accepting 12-dose weekly isoniazid-rifapentine regimen overseas with positive TST

95 %

[14]

Probability of completing 12-dose weekly isoniazid-rifapentine regimen overseas

95 %

[11, 14]

Probability of active TB during first year of resettlement for Class B1 refugeesc

1.5 %

[36]

Probability of presenting for domestic follow-up at U.S. health department

76 %

[7]

Probability of receiving TST at domestic follow-up (Class B1)

75 %

[assumption]

Probability of receiving TST at domestic follow-up (No TB class)

50 %

[assumption]

Probability of accepting latent treatment in U.S. with positive TST

77 %

[38]

Probability of completing 12-dose weekly isoniazid-rifapentine regimen in U.S.

82 %

[11]

Effectiveness of completed 12-dose weekly isoniazid-rifapentine regimen in preventing active TB

93 %

[39]

Effectiveness of partially completed 12-dose weekly isoniazid-rifapentine regimen in preventing active TB

0 %

[39]

Annual risk of progression to active TB with untreated latent disease

0.1 %

[30]

Background Mortality

Varies with age

[23]

Cost Parametersd

  

Costs of TST used in overseas screening with hypothetical protocol

  

 Base Case (average across originating countries)

$4.50

Kenyan panel physicians and [42]

 Lowest TST Cost

$3.50

Kenyan panel physicians and [42]

 Highest TST Cost

$5.15

Kenyan panel physicians and [42]

Cost of TST in U.S.

$24.00

[43]

Costs of 12 weekly 900 mg rifapentine doses through U.S. government

$72.00

[51]

Costs of 12 weekly 900 mg isoniazid doses through Global Drug Facility

$0.72

[49]

Costs of labor to administer DOT during latent treatment

  

 Average labor cost in refugee camp

$13.40

[44, 47]

 U.S.

$38.70

[47, 48]

Costs of active TB case in U.S.

$18,100

[52, 53]

  1. BCG Bacille Calmette-Guerin, DOT Directly Observed Therapy, LTBI latent tuberculosis infection, TB tuberculosis, TST tuberculin skin test, U.S. United States;
  2. aAssumes that refugees are approximately equally distributed between three categories affecting BCG specificity; bCalculated using the following formula: (% test positive + specificity – 1)/(sensitivity + specificity −1); cClass B1 refugees indicates those with abnormal chest radiograph during overseas testing, but were not diagnosed with active TB overseas; dAll costs reported in 2012 dollars;