Table 2.
Summary of definitions used in meta-epidemiological studies for assessments of allocation concealment of study participants and of blinding
| Study | Concealment of allocation | Blinding | |||||
|---|---|---|---|---|---|---|---|
| Adequate | Unclear | Inadequate | Present | Unclear | Absent | ||
| Schulz et al4 | Central randomisation; numbered or coded bottles or containers; drugs prepared by pharmacy; serially numbered, opaque, sealed envelopes; or other description that contained elements convincing of concealing | Not reported or an approach that did not fall into one of the other categories | Alternation or allocation by case record number or date of birth | Described as double blind | NA | Double blinding not reported | |
| Kjaergard et al7 | Central independent unit, sealed envelopes, or similar | NA | Not described, or open table of random numbers, or similar | Described as double blind, and used an identical placebo or similar method | Described as blinded but method not described | Open (not blind) | |
| Egger et al8 | Central randomisation; numbered or coded bottles or containers; drugs prepared by pharmacy; serially numbered, opaque, sealed envelopes; or other description that contained elements convincing of concealing | Not mentioned | Reported as alternation, open random number tables, etc | Described as double blind or included blinding of person assessing outcome | Not mentioned | Described as open or similar | |
NA=Not applicable (category not used in study).