Table 1 Model parameters, values, ranges, and sources
From: Stochastic agent-based modeling of tuberculosis in Canadian Indigenous communities
Parameter | Details | Value | Source |
|---|---|---|---|
Tuberculosis Natural History Parameters | |||
Probability of transmission (per contact) | 0.1 | Abu-Raddad [12] | |
Number of respiratory contacts (per year) | 40–1000 | Estimated by model calibration | |
Proportion of transmission occurring in community | Varied | 0.01–0.15 | Assumption |
Proportion of new infections entering latent fast state (active disease in <5 years) | Abu-Raddad [12] | ||
Adult | 0.15 | ||
Child | 0.05 | ||
Progression to active disease (per year) | Fast progressor | 1.5 | Abu-Raddad [12] |
Progression to active disease (lifetime probability, rate dependent on age at infection) | Slow progressor | 0.05 | Abu-Raddad [12] |
Proportion of active cases with extrapulmonary disease | Kivalliq surveillance data | ||
Adult | 0.11 | ||
Child | 0.042 | ||
Proportion of active cases with high transmissibility pulmonary disease | Kivalliq surveillance data | ||
Adult | 0.3 | ||
Child | 0.043 | ||
Proportion of active cases with low transmissibility pulmonary disease | Kivalliq surveillance data | ||
Adult | 0.59 | ||
Child | 0.915 | ||
Infectivity (relative to high transmissibility TB) | Abu-Raddad [12] | ||
Low transmissibility TB | 0.25 | ||
Extrapulmonary TB | 0 | ||
Spontaneous recovery rate (per year) | 0.1 | Abu-Raddad [12] | |
Relative susceptibility to re-infection | Resusceptible individuals | 0.6 | Vynnycky [33] |
Probability of TB-attributable mortality with active disease | 0.0094 | Kivalliq surveillance data | |
Population and Community Characteristics | |||
Number of communities | 7 | Census [18] | |
Initial number of households | 1890 | Census [19] | |
Average household size | 4 | Census [18] | |
Number of new households added (per year) | 30 | Census [18] | |
Proportion of population <15 years of age | 0.35 | Census [18] | |
Initial number of individuals diagnosed and on treatment | 2 | Kivalliq surveillance data | |
Initial number of individuals in different states (remaining are susceptible) | Estimated by model calibration | ||
Undiagnosed LTBI | 10–2000 | ||
Undiagnosed active TB disease | 1–50 | ||
Resusceptible (following treatment or spontaneous recovery) | 50–3000 | ||
Birth rate (per year) | Females aged 15–44 | 0.1 | Nunavut Bureau of Statistics [21] |
Mortality rate | Age-specific, estimated from Nunavut life tables | Statistics Canada [20] | |
Screening and Treatment Parameters | |||
Time to diagnosis for active TB disease | Tian [27] | ||
High | 0.5 | ||
Low | 0.64 | ||
Extrapulmonary | 0.64 | ||
Time in treatment (years) | Active TB disease | 0.6 | Kivalliq surveillance data |
Probability lost to follow-up while on treatment for active TB disease | Kivalliq surveillance data | ||
Adult | 0.06 | ||
Child | 0.04 | ||
Passive population screening for LTBI (per year) | 0.004 | TAIMA TB report [34] | |
Average time to LTBI treatment initiation for cases identified by population screening (months) | 1 | Assumption | |
Average time to completion of contact tracing (months) | 2 | Tian [13] | |
Time on treatment for LTBI (years) | 0.75 | Canadian TB Standards [24] | |
Probability LTBI treatment is completed | 0.7 | Alvarez [5] | |