Table 2

Missing data strategies for intention-to-treat and other analytic practices

Conducted true ITTMissing data strategy
No tx or FU dropoutAll FU (some tx dropout)InterpolationMissing=failureBaseline assignedLOCFCensored (end of FU) survival analysisMean substitutedOtherSample FUUnclearTotal number of ITT and/or non-ITT approaches used
No (K=104)006 (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.