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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]