Translating Confidence Intervals Graphically

Prof. Mary Ferrill clarifies how to compare ITT and Per Protocol and how to translate CIs graphically.

First, remember ITT means intention to treat, and the traditional definition is that all patients who are enrolled in the trial are included in the final analysis.

However, the most common method, modified ITT, is the last observation carried forward. If patients drop out of a trial or stop a trial sooner, those results are carried forward and make that drug look worse than the other.

For superiority studies, it is still beneficial to provide results for both ITT and PP b/c if they are different since it is probably an issue with internal validity.

As for confidence intervals, the number for general CIs on the x-axis is 0. If its measure is listed as an RR, OR, or HR, the number of the x-axis is 1.

Ultimately, when we translate CIs graphically, if delta is on the left, which means a negative value, we want to set up that favors active control goes to the left (new treatment worse). On the contrary, favors test drug goes to the right (new treatment better), and vice versa.