Make your assessment: Outcome Reporting

For your reference, here’s a chart about what kinds of missing outcomes indicate a low risk of reporting bias and which indicate a high risk of reporting bias.

Low risk of bias High risk of bias
Study protocol is available and all pre-specified outcomes are reported according to the protocol definitions Report omits some pre-specified outcomes without an appropriate explanation
Study protocol is unavailable but researchers reported all expected outcomes The study report contains different outcome definitions or analytic methods than the protocol
Report provides incomplete results about outcomes
Report fails to report an expected outcome

When you’re assessing a study for reporting bias, you should look at every outcome individually to check to see if the reported outcome matches the outcome described in the protocol.  If there’s a match, it’s a“low risk of bias.” If an outcome is missing or not completely reported, and the researchers have not explained why, it’s likely a “high risk of bias.” If you’re unsure, you can label this domain as “unclear.”

If you can tell from a study’s protocol that an outcome was collected but not reported, or the study doesn’t include enough data about a particular outcome, you can try to contact the study authors directly and ask for that unpublished data. Then, you could incorporate the results into your systematic review.