Allocation sequence | Allocation concealment | Blinding | Incomplete outcome data | Selective reporting | Other sources of | |
---|---|---|---|---|---|---|
generation | bias | |||||
Low risk | The researchers describe a random component in the sequence generation process such as: | Participants and investigators enrolling participants were not aware of assignment. | The study appears to be free of other sources of bias, etc. | |||
1. A random number table; | 1. Central allocation (e.g., telephone/web-based/pharmacy-controlled randomization); | 1. No blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; | 1. No missing outcome data; | 1. All outcomes described are included and reported in the analysis; | ||
2. Use of a computer random number generator; | 2. Sequentially numbered identical drug containers; | 2. Blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken, etc. | 2. Missing outcome data balanced in number across intervention groups, with similar reasons for missing data across groups; | 2. For registered trials, all outcomes reported are included in the analysis; | ||
3. Coin tossing; | 3. Sequentially numbered, opaque, sealed envelopes, etc. | 3. Missing data have been imputed using appropriate methods, etc. | 3. All outcomes expected to have been collected for the condition are reported, etc. | |||
4. Throwing dice; | ||||||
5. Drawing of lots, etc. | ||||||
High risk | Participants or investigators enrolling participants could possibly know the assignment. | |||||
1. Sequence generated by odd or even date of birth; | 1. Use of an open random allocation schedule; | 1. No blinding or incomplete blinding for an outcome that was likely to be affected by blinding. | 1. Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; | 1. Not all of the study’s pre-specified primary outcomes have been reported; | 1. Had a potential source of bias related to the specific study design used; | |
2. Rule based on date (or day) of admission; | 2. Date of birth; | 2. Blinding procedures could have been broken, etc. | 2. “As-treated” analysis done with substantial difference in the intervention received from that assigned at randomization, etc. | 2. One or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g., subscales) that were not pre-specified; | 2. Has been claimed to have been fraudulent, etc. | |
3. Based on hospital or clinic record number, etc. | 3. Case record number, etc. | 3. The study report fails to include results for a key outcome that would be expected to have been reported for such a study, etc. | ||||
Unclear | Randomization not described. | Insufficient evidence to permit judgment, etc. | Insufficient information to permit judgment; | 1. Insufficient reporting of attrition/exclusions to permit judgment; | Insufficient information for clear decision, etc. | Insufficient information for assessment. |
The study did not address this outcome, etc. | 2. The study did not address this outcome, etc. |