Table 3.
Reporting of variables imputed in articles using multiple imputation
| Type of studies | |||
|---|---|---|---|
| Characteristics reported | Trials | Observational studies | All studies |
| N (%)* | N (%)* | N (%)* | |
| (n = 73) | (n = 30) | (n = 103) | |
| Variables imputed | |||
| Variables imputed specified/available | 61 (84) | 28 (93) | 89 (86) |
| Number of variable(s) imputed | |||
| 1 | 31 | 8 | 39 |
| 2 | 9 | 7 | 16 |
| >2 | 17 | 10 | 27 |
| Uncleara | 4 | 3 | 7 |
| Outcome variable imputed | |||
| Yes | 55 (75) | 9 (30) | 64 (62) |
| Not stated | 12 (16) | 2 (7) | 14 (14) |
| No | 6 (8) | 19 (63) | 25 (24) |
| Type of outcome variable imputed | |||
| Numerical | 31 | 6 | 37 |
| Categorical | 16 | 2 | 18 |
| Numerical and categorical | 8 | 1 | 9 |
| Number of imputed outcome variables | |||
| 1 | 30 | 6 | 36 |
| 2 | 10 | 1 | 11 |
| >2b | 12 | 2 | 14 |
| Uncleara | 3 | 0 | 3 |
| Covariate imputed | |||
| Yes | 13 (18) | 21 (70) | 34 (33) |
| Not stated | 12 (16) | 2 (7) | 14 (14) |
| No | 48 (66) | 7 (23) | 55 (53) |
| Type of covariates imputed | |||
| Numerical | 6 | 4 | 10 |
| Categorical | 3 | 8 | 11 |
| Numerical and categorical | 3 | 8 | 11 |
| Uncleara,c | 1 | 1 | 2 |
| Number of imputed covariates | |||
| 1 | 6 | 3 | 9 |
| 2 | 2 | 7 | 9 |
| >2 | 5 | 8 | 13 |
| Uncleara | 1 | 3 | 4 |
*Unless otherwise stated.
aAuthors provided a generic statement regarding the imputed variables (e.g. the missing data in the covariates were imputed), and did not explicitly specify which outcome or covariate with missing data was imputed, so the number or type of imputed variables could not be verified.
bOne article [128] imputed missing data in 5 incomplete variables for two questionnaires recorded at 6 different waves of data collection (i.e. 60 imputed variables).
cIn one paper [98], the use of MI for imputing missing data in the covariates was derived from the cited reference, so the data type of imputed variables was not clear.