Risk of bias tables

Each included study has a Risk of bias table. Each row in the table consists of:

You can choose between a number of predefined risk of bias items, and add your own. Some risk of bias items are assessed for the study as a whole while others must be assessed at the outcome level.  

For more information on the rationale and use of use risk of bias tables, see the Handbook.

The Risk of bias tables are called Assessment of methodological quality tables in diagnostic reviews.

To activate an item

  1. Open the properties for the Risk of bias tables.
    Click the Properties icon next to the Risk of bias table heading.

  2. Select the item you wish to activate.
    Click on the item in the left pane. The predefined items are blue and cannot be modified, while user-defined items are black.  

  3. If the item must be assessed at the outcome level, add one or more outcome groups, see 'To add an outcome level group'.

  4. Select the Activated check box.
    If the check box is grayed out, it is because outcome groups have not yet been specified, see above.

  5. Click OK.
    The properties window closes and the new item is added to the table. If you defined multiple outcome groups, there will be a row for each.

To add a user-defined item

  1. Open the properties for Risk of bias tables.
    Click the Properties icon next to the Risk of Bias Table heading, and go to the Risk of Bias Tables tab.

  2. Add the new item.
    Click the Add button beneath the left pane.
    The item will be created with the default name 'New item'.  

  3. Edit the name in the Item field.

  4. Input the Full Question.

  5. Specify the assessment level.

  6. Activate the item (see above).

  7. Click OK.

To specify a user-defined order

  1. Open the properties for the Risk of bias tables.

  2. Click one of the risk of bias items you wish to reorder.

  3. Click Move Dn or Move Up to move the item.

  4. Repeat steps 3 and 4, until the items are in the desired order.

  5. Click OK. 

Study or outcome level assessment

Some risk of bias items are assessed for the study as a whole (e.g. 'Allocation concealment?') while others must be assessed at the outcome level (e.g. 'Blinding').

To use assessment at the outcome level,you must:

To add an outcome level group

  1. Open the properties for the Risk of bias tables.
    Click the Properties icon next to the Risk of bias table heading, and go to the Risk of Bias Tables tab.

  2. Select  the item you wish to change.
    Click on the item in the left pane.

  3. Click the Add button to the right of the list of outcome groups.
    A new group with the label 'All outcomes ' is created.

  4. Modify the label of the outcome group.

  5. Select the outcomes that should be part of the group from the list below.

  6. Repeat steps 3 to 5 to create the number of groups you require.

  7. If needed, activate the item.

  8. Click OK.

Blank entries and publication

If a Risk of bias table contains an item with an empty description field and the judgement is set to 'Unclear risk', this row of the table will not be published with the review in The Cochrane Library. This is a way for authors to include an item for one study, but not others.

Changes from RevMan 5.0

The risk of bias item names, judgements  and explanations were updated in RevMan 5.1.

When creating a new review, the Risk of bias table will contain seven risk of bias items. The item 'Blinding (performance bias and detection bias)' has been split in to two items: 'Blinding of participants and personnel (performance bias)' and 'Blinding of outcome assessment (detection bias)'. All items in the Risk of bias table will be activated by default.

The table below shows the mapping between Risk of bias items created in RevMan 5 opened in RevMan 5.1 or later:

RevMan 5.0

When edited in RevMan 5.1

Item

Full question

Bias

Explanation

Adequate sequence generation?

Was the allocation sequence adequately generated?

Random sequence generation (selection bias)

Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence

Allocation concealment?

Was allocation adequately concealed?

Allocation concealment (selection bias)

Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment

Blinding?

Was knowledge of the allocated interventions adequately prevented during the study?

Blinding (performance bias and detection bias)

Performance bias or detection bias due to knowledge of the allocated interventions after assignment

Incomplete outcome data addressed?

Were incomplete outcome data adequately addressed?

Incomplete outcome data (attrition bias)

Attrition bias due to amount, nature or handling of incomplete outcome data

Free of selective reporting?

Are reports of the study free of suggestion of selective outcome reporting?

Selective reporting (reporting bias)

Reporting bias due to selective outcome reporting

Free of other bias?

Was the study apparently free of other problems that could put it at a high risk of bias?

Other bias

Bias due to problems not covered elsewhere in the table

Free of bias X?

[entered by the user]

Free of bias X?

[entered by the user]