Table 3 Comparison of cluster 1 and cluster 2 studies (mean ± SD)
|  | Characteristic | Cluster 1 | Cluster 2 | p-value†|
|---|---|---|---|---|
Study-related | Publication date (months after first) | 38 ± 8 | 22 ± 17 | 0.05 |
|  | Study size (number of patients) | 136 ± 106 | 75 ± 35 | 0.23 |
|  | Jadad score (1–5) | 2.9 ± 1.5 | 2.0 ± 1.4 | 0.24 |
|  | All three factors combined | 34 ± 13 | 50 ± 9 | 0.01 |
Patient-related | Age (years) | 68 ± 4 | 70 ± 3 | 0.24 |
|  | Baseline creatinine (mg/dl) | 1.6 ± 0.4 | 2.2 ± 0.6 | 0.09 |
|  | Diabetes mellitus (%) | 43 ± 13 | 45 ± 13 | 0.93 |
|  | Female (%) | 31 ± 14 | 22 ± 9 | 0.31 |
|  | Contrast volume (ml) | 158 ± 61 | 122 ± 46 | 0.11 |