Missing data strategies for intention-to-treat and other analytic practices
| Conducted true ITT | Missing data strategy | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No tx or FU dropout | All FU (some tx dropout) | Interpolation | Missing=failure | Baseline assigned | LOCF | Censored (end of FU) survival analysis | Mean substituted | Other | Sample FU | Unclear | Total number of ITT and/or non-ITT approaches used | |
| No (K=104) | 0 | 0 | 6 (4%) | 23 (17%) | 1 (1%) | 22 (16%) | 25 (18%) | 3 (2%) | 2 (1%) | 38 (27%) | 17 (12%) | 139 |
| Yes (K=61) | 1 (1%) | 2 (2%) | 14 (13%) | 14 (13%) | 1 (1%) | 12 (11%) | 23 (22%) | 2 (2%) | 1 (1%) | 11 (10%) | 24 (23%) | 105 |
| Total (K=165) | 1 (<1%) | 2 (<1%) | 20 (7%) | 37 (16%) | 2 (<1%) | 34 (13%) | 48 (19%) | 5 (2%) | 3 (1%) | 49 (19%) | 41 (16%) | 259* |
Column description: (1) no treatment (tx) or follow-up (FU) dropout, (2) All followed up (some dropout; there were dropouts from treatment, but all participants, including dropouts were followed up), (3) interpolation (used a statistical analysis that interpolated missing data, eg, mixed effects model interpolation), (4) missing= failure (assumed that missing data=failure, eg, relapse), (5) baseline assigned (assigned a person's baseline score if the outcome score was missing), (6) LOCF (used an imputation strategy of last observation carried forward), (7) censored (end of FU; data presented in a survival analysis), (8) mean substituted (used the mean for each person across available assessments/timepoints), (9) other (other imputation strategy), (10) sample FU (conducted analyses on the sample of participants that the researchers was able to follow-up) and (11) unclear (no information provided/unclear).
*The values in each row of table 2 do not sum to the total number of studies in the first column (ie, ‘Conducted ITT’) due to 42 studies utilizing multiple missing data strategies.
FU, follow up; ITT, intention-to-treat; LOCF, last observation carried forward; tx, treatment.