| Δ Baseline to year 1 | Δ Baseline to year 2 | Δ Year 1 to year 2 | |
| Total score | |||
| Abatacept | 1.07 | 1.55 | 0.46 |
| Placebo/abatacept | 2.40 | 3.17 | 0.75 |
| Erosion score | |||
| Abatacept | 0.62 | 0.84 | 0.21 |
| Placebo/abatacept | 1.44 | 1.69 | 0.25 |
| Joint space narrowing score | |||
| Abatacept | 0.45 | 0.71 | 0.24 |
| Placebo/abatacept | 0.95 | 1.48 | 0.50 |
Baseline is day 1 of study. All randomised and treated patients who entered the open-label period and had radiographs at baseline and year 1. Baseline and year 1 radiographs were re-read at day 729. Placebo patients were switched to abatacept in the long-term extension (year 2). All patients received background methotrexate.