Unfair comparison

Lots of missing people

Be careful with treatment comparisons where what happened was not measured in lots of people.

Sometimes, outcomes were not measured in some of the people in a treatment comparison, so those people were left out of the results of the study. When lots of people are left out of the results, or there is a big difference between the comparison groups in how many people were left out, the results can make the effects of the treatments seem bigger or smaller than they are.

For example, people may stop taking part in a study comparing treatments because the treatment they got was not helping them, or because it was making them worse. For example, patients taking thickened fluids may stop taking these as they do not feel they are helping them or feel that the treatment is making their swallowing more difficult. If those people are left out of the results, the results can make the effects of that treatment seem bigger than they are.

REMEMBER: Think about whether lots of people who started out in a study comparing treatments were missing in the results.