Table 1

LTBI adherence model inputs

Parameter or inputBase caseRangeDistributionReference
Cohort population data
 Age40Not variedNormalAssumption
Tuberculosis-related probabilities
 Prob(Annual TB activation | No LTBI treatment)0.0030.001–0.005BetaInternational Union Against Tuberculosis, Committee of Prophylaxis11
 Prob(Cure | Treatment)0.870.85–0.89BetaLienhardt et al 43
 Prob(Secondary TB transmissions per active TB case)0.550.75x–1.25x*UniformSalpeter and Salpeter44
 Prob(TB reactivation within 2 years | TB treatment comp)0.0360.033–0.039BetaJasmer et al 45, Khan et al 46
 Prob(death with active TB)0.0750.061–0.093BetaPublic Health Agency of Canada10
LTBI treatment clinical outcomes
INH treatment outcomes
 Probability of full completion of INH therapy0.610.57–0.65BetaDobler and Marks, Aspler et al, Pina et al, Page et al, Menzies et al, Lardizabal et al 12–17
 Subcategories in the low-adherence group:
 Probability of completing 6–9 months of INH0.33Not variedN/ADobler and Marks12
  Probability of completing 3–6 months of INH0.37Not variedN/ADobler and Marks12
  Probability of completing 0–3 months of INH0.30Not variedN/ADobler and Marks12
  Prob(stopping INH in first month | Adverse event)0.52Not variedN/ALi et al 3
  Prob(major INH adverse event requiring stoppage)0.060.045–0.075BetaPina et al, Page et al, Menzies et al, Lardizabal et al 14–17
  Prob(death | major INH adverse event)0.00012Salpeter47
  Reduction in 5-year active TB incidence with:
   Full INH completion93%70%–99.9%BetaInternational Union Against Tuberculosis Committee of Prophylaxis11
   6–9 months of INH completion69%42%–91%BetaInternational Union Against Tuberculosis Committee of Prophylaxis11
  3–6 months of INH completion31%33%–40%BetaInternational Union Against Tuberculosis Committee of Prophylaxis11
   0–3 months of INH completion0%Not variedN/AInternational Union Against Tuberculosis Committee of Prophylaxis11
RIF treatment outcomes
 Prob(RIF initiation | INH failure)0.50.25–0.75UniformAssumption
 Probability of full completion of RIF therapy0.750.73–0.79BetaAspler et al, Pina et al, Page et al, Menzies et al, Lardizabal et al 13–17
 Risk of RIF adverse event requiring stoppage0.029Not variedN/APina et al, Page et al, Menzies et al, Lardizabal et al 14–17
 Reduction in 5-year active TB incidence with:
   Full RIF completion77.5%65%–90%UniformReichman et al 22
   Partial RIF completion0%Not variedN/AAssumption
Costs data (2016 Canadian dollars)
 LTBI treatment and care with INH
 (full completion cost; reduced for partial completion)
$C9350.75x–1.25x*UniformBCCDC
 LTBI treatment and care with RIF
 (full completion cost; reduced for partial completion)
$C5450.75x–1.25x*UniformBCCDC
 Cost of TB diagnosis$C3900.75x–1.25x*UniformMenzies et al 24
 Annual outpatient TB treatment and care$C15900.75x–1.25x*UniformMenzies et al 24
 Annual inpatient TB treatment and care$C11 6400.75x–1.25x*UniformMenzies et al 24
 Cost of major adverse event$C7100.75x–1.25x*UniformTan et al 48
Utilities
 Healthy or asymptomatic LTBI1N/AAssumption
 LTBI on treatment0.820.9x–1.1x*UniformGuo et al 26
 Active TB0.620.9x–1.1x*UniformGuo et al 26
Intervention impact on adherence ratesRR†
 Adherence incentives1.040.97–1.13Log-normalLutge et al 28
 Enhanced adherence counselling1.091.01–1.15Log-normalMills et al 29
 Peer support intervention1.101.00–1.29Log-normalHirsch-Moverman et al,19 Kominski et al 49
 Weekly SMS adherence support1.231.13–1.35Log-normalWald et al 30
  • *A value was drawn from a uniform distribution across this range and multiplied by the base case during probabilistic analyses.

  • †Relative risk: multiplied by the probability of full adherence to the respective regimens to derive a proportion of adherent and non-adherent individuals.

  • BCCDC, British Columbia Centre for Disease Control; INH, isonicotinylhydrazide; LTBI, latent tuberculosis infection; RIF, rifampin; SMS, short message service; TB, tuberculosis.