Table 3.
Summary of quality components and quality scales most used in Cochrane systematic reviews and systematic reviews published in paper based journals analysed in study. Values are numbers (percentages) unless stated otherwise
| Variable | Cochrane systematic reviews (n=809) | Paper based systematic reviews (n=156) | Difference between proportions (95% CI) | P value (χ2 test) |
|---|---|---|---|---|
| Quality components*: | ||||
| Allocation concealment | 639 (79.0) | 37 (23.7) | 55.3 (48.0 to 62.5) | <0.0001 |
| Any type of blinding | 604 (74.7) | 64 (41.0) | 33.7 (25.4 to 41.9) | <0.0001 |
| Generation of allocation sequence | 209 (25.8) | 26 (16.7) | 9.1 (2.6 to 15.8) | 0.0146 |
| Similarity of groups at baseline | 142 (17.6) | 17 (10.9) | 6.7 (1.1 to 12.2) | 0.0402 |
| Description of outcomes | 110 (13.6) | 14 (9.0) | 4.6 (−0.5 to 9.7) | 0.1142 |
| Intention to treat analysis | 240 (29.7) | 19 (12.2) | 17.5 (11.5 to 23.5) | <0.0001 |
| Sample size | 99 (12.2) | 24 (15.4) | −3.2 (−9.2 to 3.0) | 0.2805 |
| Losses to follow-up | 561 (69.3) | 52 (33.3) | 36.0 (28.0 to 44.1) | <0.0001 |
| Quality scale: | ||||
| Schulz | 37 (4.6) | 2 (1.3) | 3.3 (1.0 to 5.6) | 0.0560 |
| Jadad | 84 (10.4) | 29 (18.6) | −8.4 (−14.9 to −2.0) | 0.0025 |
| Cochrane Group | 133 (16.4) | 0 (0) | 16.4 (13.9 to 19.0) | <0.0001 |
| Other | 35 (4.3) | 20 (12.8) | −8.5 (−13.9 to −3.1) | <0.0001 |
*
More than one answer possible.