2-6 Peoples’ outcomes should be assessed similarly

If an outcome is measured differently in two comparison groups, differences in that outcome may be due to how the outcome was measured rather than because of the treatment received by people in each group. For example, if outcome assessors believe that a particular treatment works and they know which patients have received that treatment, they ma y be more likely to observe better outcomes in those who have received the treatment. One way of preventing this is to keep outcome assessors unaware (“blind”) of which people have been allocated to which treatment. This is less important for “objective” outcomes like death than for “subjective” outcomes like pain.

Be cautious about relying on the results of treatment comparisons if outcomes were not measured in the same way in the different treatment comparison groups. The results of such comparisons could be misleading.