Control (%) | Treatment (%) | RRR (%) | ARR (%) | Sample size in each group | |
---|---|---|---|---|---|
1 Example of the relative risk reduction model | |||||
Low baseline risk | 20 | 10 | 50 | 10 | 195 |
Medium baseline risk | 60 | 30 | 50 | 30 | 41 |
High baseline risk | 90 | 45 | 50 | 45 | 14 |
2 Example of the absolute risk reduction model | |||||
Low baseline risk | 20 | 10 | 50 | 10 | 195 |
Medium baseline risk | 60 | 50 | 17 | 10 | 387 |
High baseline risk | 90 | 80 | 11 | 10 | 195 |
CSA + placebo† (%) | CSA + MTX† (%) | RRR (%) | ARR (%) | Sample size in each group | |
---|---|---|---|---|---|
3 CSA + MTX compared with CSA alone | |||||
Low baseline risk* | 50 (n = 28) | 25 (n = 32) | 50 | 25 | 57 |
High baseline risk | 79 (n = 29) | 50 (n = 26) | 37 | 29 | 40 |
SSZ† (%) | COBRA† (%) | RRR (%) | ARR (%) | Sample size in each group | |
---|---|---|---|---|---|
RRR = (1 − (outcome rate treatment group divided by outcome rate controls)×100); ARR = (outcome rate control group – outcome rate treatment group). | |||||
Sample size calculation based on α = 0.05, β = 0.20, two sided. | |||||
CSA, ciclosporin; MTX, methotrexate; SSZ, sulfasalazine; COBRA treatment, step down prednisolone + MTX + SSZ. | |||||
*Risk groups based on baseline radiographic damage (below or above the median); †percentage of patients with radiographic progression larger than the median. | |||||
4 COBRA treatment compared with SSZ alone | |||||
Low baseline risk* | 40 (n = 30) | 18 (n = 38) | 54 | 22 | 68 |
High baseline risk | 82 (n = 34) | 58 (n = 33) | 30 | 25 | 51 |