Changes in 5-year incidence rate of total hip (THR) or total knee replacement (TKR) in incident rheumatoid arthritis (RA) patients following introduction of biological DMARDs compared with secular trends in age, sex and municipality-matched general population controls (GPC)
| Cohort | n THR/TKR | Baseline incidence rate/1000 person years | Δ per year* pre-2002 | Δin level 2003 | Δ per year post-2003 | |
|---|---|---|---|---|---|---|
| TKR | RA | 865 | 5.87 | +0.19 | – | -0.20 |
| GPC | 2438 | 0.42 | +0.21 | – | +0.08 | |
| THR | RA | 935 | 8.72 | -0.38 | +2.23 | -0.38 |
| GPC | 4744 | 2.89 | +0.11 | – | +0.02 | |
Stepwise backward elimination to produce most parsimonious model: p-entry <0.05 and p-exit >0.2. *Δ per year based on biannual data.