2-7 All should be followed up

People in treatment comparisons who are not followed up to the end of the study may have worse outcomes than those who are followed up. For example, they may have dropped out because the treatment was not working or because of side effects. If those people are excluded, the findings of the study may be misleading.

Be cautious about relying on the results of treatment comparisons if many people were lost to follow-up, or if there was a big difference between the comparison groups in the percentages of people lost to follow-up. The results of such comparisons could be misleading.