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Table 2 Model Pathogenetic Variables and Assumptions

From: Cost-effectiveness of novel vaccines for tuberculosis control: a decision analysis study

Variable

Value

Source

HIV Infection

  

   Annual risk of progression - asymptomatic to AIDS

7%

[22, 62]

   Annual risk of death - early HIV (asymptomatic)

4.6%

[22]

   Annual risk of death - clinical AIDS

22%

[22]

   Median survival with early HIV

9.8 yrs

[22, 62]

   Median survival with clinical AIDS

9 months

[22]

Risk of developing active TB disease

  

   HIV uninfected

  

Within 2 years of new TB infection

5%

[17, 63]

Within 2 years of re-infection after cured TB disease

1%

[64, 65]

Late re-activation from longstanding latent TB*

0.1%/year

[18, 19]

   Early HIV

  

Within 2 years of new TB infection

33%

Extrapolated

Within 2 years of re-infection after cured TB disease

33%

Assumption

Late re-activation from longstanding latent TB*

3.4%/year

[23, 66, 67]

   Clinical AIDS

  

Within 2 years of new TB infection

100%

[25, 68–71]

Within 2 years of re-infection after cured TB disease

100%

Assumption

Late re-activation from longstanding latent TB*

33%/year

[23]

Untreated Smear Positive TB Outcomes (HIV-negative)

  

   Spontaneous resolution

25%

[72]

   Relapse after spontaneous resolution

2.5%/year

[72, 73]

   Mortality rate within 2 years

33% at 1 year; 50% at 2 years

[74]

Untreated Smear Positive TB Outcomes (HIV-positive)

  

   Spontaneous resolution

0%

Assumption

   Mortality rate within 2 years

100%

Assumption

Treated Smear Positive TB Outcomes (HIV-negative)

  

   Relapse after cure (total over next 2 years)

3.0%

[75–79]

   Cure rate if default (single drug resistant or drug sensitive)**

62.4%

[80–83]

Effect of Drug Sensitivity on Treatment Outcomes

  

   Relative risk of treatment failure - single drug resistant

2.0

[84]

   Relative risk of treatment failure - multi-drug resistant

10.5

[84]

   Relative risk of death - single drug resistant

1.0

[84]

   Relative risk of death - multi-drug resistant

4.5

[84]

Multi-Drug Resistant TB Treatment Outcomes

  

   Completed/Cured

68.6%

[85]

   Default/Failed/Transferred

17.1%

[85]

   Died

14.2%

[85]

Treated Smear Positive TB Outcomes (HIV-positive)

  

   Relative risk of death during TB treatment with HIV infection

2.25

[24, 26, 86, 87]

   Relapse after successful TB treatment (cured)

3.1%

[88–90]

  1. * Assumes rate of reactivation beyond 2 years after TB infection is the same whether it is after a first infection or after re-infection
  2. ** Transfer out considered equivalent to default [91]. Overall cure rate if default based on timing of default [73], and cure rates from trials of very short course treatment [81–83].