Table 14:
Natural History Inputs for Treatment as Usual
| Model Parameter | Mean (SE)a,b | Distribution (Parameters)b | Reference |
|---|---|---|---|
| Probability of remission in TAU (initial treatment at baseline) • Estimated per monthc |
0.114 (0.012) • 0.059 (0.002) |
Beta (α: 77.178; β: 599.822) | Greden et al, 201957 |
| Probability of relapse in TAU • Estimated per monthc |
0.233 (0.14) • 0.043 (0.025) |
Beta (α: 1.891; β: 6.226) | Sim et al, 2015106 |
| Risk ratio for remission, next treatment vs. initial treatment in step 2d | 0.83 | NA (fixed) | Rush et al, 20068 |
| Probability of transitioning to the well state, in those with initial remission (maintenance treatment phase)e • Estimated per monthc,e |
0.66 (0.07) • 0.086 (0.006) |
Beta (α: 29.565; β: 15.231) | Williams et al, 2009108 |
| Probability of side effects due to treatment with antidepressants in TAU | 0.153 (0.015) | Beta (α: 92.718; β: 513. 282) | Greden et al, 201957 |
| Annual probability of all-cause mortality, starting at age 48 y • Estimated per monthc |
0.00198 • 1.65 × 10−4 |
NA (fixed, Life Table) | Ontario Life Tables 2016–2018, Statistics Canada, 2020107 |
| Risk ratio for all-cause mortality, no remission vs. remission | 1.7 (0.026) | Lognormal (mean: 0.531; SE: 0.008) | Tanner et al, 201987 |
| Annual probability of suicide, in people with no remission • Estimated per monthc |
0.0004 • 3.33 × 10−5 |
NA (fixed) | Tanner et al, 201987 |
| Annual probability of suicide, in people with remission • Estimated per monthc |
0.0001 • 8.33 × 10−6 |
NA (fixed) | Tanner et al, 201987 |
Abbreviations: NA, not applicable; SE, standard error; TAU, treatment as usual.
Standard errors were estimated whenever data were available; those associated with the probability of transitioning to the well state were assumed to be 10% of the mean. Input parameters presented as the point estimates (without SEs) were assumed to be fixed, given the limited data.
Beta distributions were assigned to probability estimates in probabilistic analysis where applicable. Standard error of the mean (SE) was estimated from 95% confidence intervals or from original data. Two parameters of the beta distribution (α, β) were derived from the mean and SE (stated for each model parameter). Formulas for these calculations, derived from the mean and SE, are: α = ([Mean2] × [1 – Mean])/([SE2] – Mean); β = ([{1 – Mean} × {1 – Mean}] × Mean)/([SE2] – 1). Lognormal distributions were assigned for risk ratio inputs (wherever possible), using two distribution parameters: μ (mean of logs) and σ (SE, standard deviation of logs). Distribution parameters values were based on original data; further adjustments and transformations to the model cycle length of 1 month were performed (see footnote c).
Markov model used a cycle length of 1 month and all rates and probabilities were adjusted appropriately.
When a person does not benefit from initial treatment and starts a second treatment, the probability of remission is decreased (by 0.83 times) as shown in the STARD∗D trial for the step 2 treatment: probability of remission with step 1 ÷ probability of remission with step 2: 0.366/0.306 = 0.83.8
Well health state was included in a scenario analysis only.