Handling of, and assessing the risk of bias associated with missing participant data in Cochrane and non-Cochrane SRs
| Overall (N=202) | Cochrane SR (N=98) | Non-Cochrane SR (N=104) | p Value* | |
|---|---|---|---|---|
| Reported plans for handling missing categorical data | <0.0001 | |||
| Using complete case analysis | 17 (8.5%) | 15 (15.5%) | 2 (2.0%) | |
| Assuming no participants with missing data had the event | 8 (4.0%) | 7 (7.2%) | 1 (1.0%) | |
| Assuming all participants with missing data had the event | 5 (2.5%) | 4 (4.1%) | 1 (1.0%) | |
| Assuming participants with missing data had same event rate as those followed up in respective randomisation groups | 2 (1.0%) | 1 (1.0%) | 1 (1.0%) | |
| Using worst case scenario† | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | |
| Using best case scenario‡ | 1 (0.5%) | 0 (0.0%) | 1 (1.0%) | |
| Using whatever assumptions the included trials used | 1 (0.5%) | 1 (1.0%) | 0 (0.0%) | |
| Using other assumption(s) | 15 (7.5%) | 12 (12.4%) | 3 (3.0%) | |
| No method described | 150 (75.4%) | 57 (58.8%) | 93 (91.2%) | |
| Reported a planned sensitivity analyses for handling missing participant data | ||||
| Yes, clearly for categorical outcomes | 12 (5.9%) | 10 (10.2%) | 2 (1.9%) | 0.02 |
| Yes, but unclear as to whether for categorical or continuous outcomes | 11 (5.4%) | 9 (9.2%) | 2 (1.9%) | 0.03 |
| Provide a justification for any of the method(s) for handling missing participant data | 4 (2.0%) | 4 (4.2%) | 0 (0.0%) | <0.0001 |
| Assessed the risk of bias associated with missing participant data | ||||
| Yes, using the Cochrane RoB tool (incomplete outcome data (attrition bias)) | 85 (42.1%) | 76 (77.6%) | 9 (8.7%) | <0.0001 |
| Yes, using a tool other than the Cochrane RoB tool (eg, Jadad’s scale) | 47 (23.3%) | 6 (6.1%) | 41 (39.4%) | |
| Discussed the implications of missing participant data | ||||
| Yes, in the Results section | 23 (11.4%) | 19 (19.4%) | 4 (3.9%) | |
| Yes, in the Discussion section | 20 (10.0%) | 16 (16.3%) | 4 (3.9%) | |
*p Value for the difference between Cochrane and non-Cochrane SRs.
†Worst case scenario: assuming all participants with missing data in the intervention group had the event but none in the control group did.
‡Best case scenario: assuming that all participants with missing data in the control group had the event but none in the intervention group did.
RoB; Risk of Bias; SR, systematic review.