Table 1.
Base case inputs and assumptions
| Variable | Value | Range | Distribution | |
|---|---|---|---|---|
| Key variables | ||||
| Time horizon | Lifetime | – | – | |
| Cycle length (weeks) | 12 | – | – | |
| Discount rate (%) | 3.5 | – | – | |
| Starting age in the model (years) | 31.2 | SD 0.51 | Normal, truncated | |
| Sex, proportion of males (%) | 57.1 | – | – | |
| Standardized mortality rate (SMR) | ||||
| Male | 1.63 | SE 0.17 | Lognormal | |
| Female | 1.38 | SE 0.46 | Lognormal | |
| Baseline scores | ||||
| BASDAI score | 6.49 | SD 0.12 | Normal, truncated | |
| BASFI score | 5.01 | SD 0.19 | Normal, truncated | |
| Baseline utility | 0.43 | SD 0.03 | Normal, truncated | |
| Probability of week-12 responsea | ||||
| Conventional therapy | 0.2069 | SD 0.02091 | Beta | |
| Golimumab | 0.4575 | SD 0.08065 | Lognormal | |
| Adalimumab | 0.4642 | SD 0.08375 | Lognormal | |
| Certolizumab pegol | 0.5578 | SD 0.117 | Lognormal | |
| Etanercept | 0.3974 | SD 0.07659 | Lognormal | |
| Week-12 scores | ||||
| Conventional therapy | ||||
| BASDAI score | 5.20 | – | Normal, truncated | |
| BASFI score | 4.34 | – | Normal, truncated | |
| Golimumab | ||||
| BASDAI score | 3.35 | – | Normal, truncated | |
| BASFI score | 2.71 | – | Normal, truncated | |
| Adalimumab | ||||
| BASDAI score | 4.17 | – | Normal, truncated | |
| BASFI score | 3.60 | – | Normal, truncated | |
| Certolizumab pegol | ||||
| BASDAI score | 3.35 | – | Normal, truncated | |
| BASFI score | 2.45 | – | Normal, truncated | |
| Etanercept | ||||
| BASDAI score | 4.50 | – | Normal, truncated | |
| BASFI score | 3.74 | – | Normal, truncated | |
| Week-24 scores | ||||
| Conventional therapy | ||||
| BASDAI score | 5.22 | – | Normal, truncated | |
| BASFI score | 4.36 | – | Normal, truncated | |
| TNFis | ||||
| BASDAI score | 1.00 | – | Normal, truncated | |
| BASFI score | 0.92 | – | Normal, truncated | |
| Week-36 scores | ||||
| Conventional therapy | ||||
| BASDAI score | 5.23 | – | Normal, truncated | |
| BASFI score | 4.38 | – | Normal, truncated | |
| TNFis | ||||
| BASDAI score | 0.85 | – | Normal, truncated | |
| BASFI score | 0.88 | – | Normal, truncated | |
| Week-48 scores | ||||
| Conventional therapy | ||||
| BASDAI score | 5.25 | – | Normal, truncated | |
| BASFI score | 4.39 | – | Normal, truncated | |
| TNFis | ||||
| BASDAI score | 0.93 | – | Normal, truncated | |
| BASFI score | 0.87 | – | Normal, truncated | |
| Week-60 scores | ||||
| Conventional therapy | ||||
| BASDAI score | 5.26 | – | Normal, truncated | |
| BASFI score | 4.41 | – | Normal, truncated | |
| TNFis | ||||
| BASDAI score | 0.92 | – | Normal, truncated | |
| BASFI score | 0.85 | – | Normal, truncated | |
| Probability of infections | ||||
| Conventional therapy | 0.2096 | SD 0.02222 | Beta | |
| Golimumab | 0.2315 | SD 0.06379 | Lognormal | |
| Adalimumab | 0.2674 | SD 0.06028 | Lognormal | |
| Certolizumab pegol | 0.24945 | – | – | |
| Etanercept | 0.242 | SD 0.08712 | Lognormal | |
| Probability of SAEs | ||||
| Conventional therapy | 0.01641 | SD 0.006948 | Beta | |
| Golimumab | 0.01541 | SD 0.02999 | Lognormal | |
| Adalimumab | 0.07749 | SD 0.1025 | Lognormal | |
| Certolizumab pegol | 0.046 | – | – | |
| Etanercept | 0.02995 | SD 0.04751 | Lognormal | |
| 12-week cycle costs (drug acquisition, drug administration, initiation/monitoring) | ||||
| Golimumab | First 12 weeks | 2667.72 | SE 800.315 | Gamma |
| Subsequent cycles | 2195.22 | SE 658.566 | Gamma | |
| Adalimumab | First 12 weeks | 2667.72 | SE 800.315 | Gamma |
| Subsequent cycles | 2195.22 | SE 658.566 | Gamma | |
| Certolizumab pegol | First 12 weeks | 554.88 | SE 166.463 | Gamma |
| Subsequent cycles | 2227.38 | SE 668.214 | Gamma | |
| Etanercept | First 12 weeks | 2699.88 | SE 809.963 | Gamma |
| Subsequent cycles | 2227.38 | SE 668.214 | Gamma | |
| Other costs | ||||
| Long-term costs | Intercept | 1284.186 | SE 385.2558 | Normal |
| Coefficient BASFI score | 0.213 | SE 0.0639 | Normal | |
| Infection | 1483.226 | SE 444.97 | Gamma | |
| Other variables | ||||
| Annual disease progression (conventional therapy) | 0.07 | SD 0.021 | Normal, truncated | |
| Annual disease progression post-Week 260 (TNFis) | 0.50b | – | – | |
| Annual discontinuation rate (TNFis) | 5.0 | SE 0.015 | Beta | |
| Intercept for utility score | 0.10034 | SE 0.11562 | Normal | |
| Coefficient for utility score | Sex | 0.00126 | SE 0.04384 | Normal |
| Age | −0.0044 | SE 0.0031 | Normal | |
| Per 1 unit change in BASDAI | −0.05735 | SE 0.01343 | Normal | |
| Per 1 unit change in BASFI | −0.0312 | SE 0.01302 | Normal | |
| Disutility for SAEs | 0.01 | SE 0.003 | Normal | |
BASDAI bath ankylosing spondylitis disease activity index, BASFI bath ankylosing spondylitis functional index, SAE serious adverse event, SD standard deviation, SE standard error, TNFi tumor necrosis factor inhibitor
aAccording to a BASDAI50 response (this efficacy measure was used in the model base case to reflect Scottish clinical practice)
bAssumed to occur at 50% of the rate of progression on conventional therapy