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Table 1 Model parameters: base-case values, assumptions and ranges used in the sensitivity analyses

From: Revisiting annual screening for latent tuberculosis infection in healthcare workers: a cost-effectiveness analysis

Parameter

Base-case value

Range

References

Prevalence of latent tuberculosis infection (LTBI) at the time of hire (before baseline testing)

10.0%

(10–30%)

[6]

Probability of being recently infected among those with LTBI at baseline

16.7%

(10–30%)

Model assumption

Proportion of healthcare workers (HCWs) performing high-risk activities

27.0%

(10–30%)

[16]

Annual risk of TB exposure in HCWs performing high-risk activities:

 Base-case scenario

4.4%

(0–40%)

[12, 17]

 Alternate scenario assuming higher risks

13.1%

(0–40%)

[17, 18]

Annual risk of TB exposure in HCWs performing intermediate-risk activities:

 Base-case scenario

1.3%

(0–15%)

[12, 17]

 Alternate scenario assuming higher risks

4.4%

(0–15%)

[17, 18]

Probability of acquiring new TB infection given exposure

22.9%

(0–30%)

[18]

Adherence of HCWs to annual screening (mandatory for continued employment)

100%

(50–100%)

Model assumption

Probability that TB exposure is recognised

75.0%

(50–100%)

Model assumption

Probability of being screened after TB exposure is recognised (tuberculin skin test)

88.8%

(50–100%)

[19]

Probability of being screened after TB exposure is recognised (QuantiFERON®-TB-Gold)

95.0%

(50–100%)

[20]

Sensitivity of tuberculin skin test in serial testing

95.0%

(70–100%)

[26, 29]

Sensitivity of QuantiFERON®-TB-Gold in serial testing

95.0%

(70–100%)

[27, 28]

Specificity of tuberculin skin test for serial testing, after baseline negative test

97.0%

(70–100%)

[23]

Specificity of QuantiFERON®-TB-Gold for serial testing after baseline negative test

95.0%

(70–100%)

[6, 11]

Efficacy of isoniazid preventive treatment

90.0%

(80–100%)

[42]

Probability that isoniazid is recommended to worker after conversion on repeat testing

100%

(50–100%)

Model assumption

Probability that worker with conversion starts isoniazid treatment, after recommendation to take it

82.9%

(50–100%)

[43]

Probability that isoniazid treatment is completed, once started

47.3%

(40–100%)

[43]

Risk of mild isoniazid-induced hepatitis

0.1%

 

[44]

Risk of fatal isoniazid-induced hepatitis

0.002%

 

[44]

Annual risk of progression from LTBI to active TB for recently infected (≤2 years since onset of infection)

2.5%

(0–2.5%)

[21]

Annual risk of progression from LTBI to active TB for remotely infected (>2 years since onset of infection)

0.1%

 

[22]

Risk of death from active TB

4.6%

(0–10%)

[45]

Risk of major adverse event with treatment for active TB

5.1%

 

[44]

Risk of death, given major adverse event with treatment for active TB

1.5%

 

[44]

Costs (in 2015 CAN dollars; $1 CAN = $0.77 US)

 Diagnosis for active TB disease

$354

 

[46,47,48]

 Inpatient treatment of active TB disease

$13,063

 

[49]

 Outpatient treatment of active TB disease

$3,748

 

[50]

 Tuberculin skin test

$15

($10–30)

[51]

 QuantiFERON®-TB-Gold

$50

($10–50)

[51]

 Complete treatment for LTBI

$591

 

[52]

 Incomplete treatment for LTBI

$272

 

[52]

 Isoniazid-induced hepatitis (mild)

$400

 

[53]

 Isoniazid-induced hepatitis (fatal)

$13,078

 

[53]

Quality of life adjustments: QALYs lost per year

 Active TB disease treatment

0.15

(0.10–0.30)

[24, 25]

 Latent TB treatment

0.03

(0–0.05)

[24, 25]