Ineffective therapies can appear to produce convincing improvements in diseases.
ID: 134418 • Letter: I
Question
Ineffective therapies can appear to produce convincing improvements in diseases. Piantadosi (Sec 6.6.1, optional course text in syllabus) claims that there are at least 3 mechanisms by which this happens: (1) spontaneous improvements in the disease, (2) regression to the mean, and (3) the placebo effect. Consider the following scenario: Patients with severe emphysema are enrolled into a blinded, randomized trial testing Drug A vs Placebo. The outcome of interest is a measure of exercise capacity known as the "Six-Minute Walk Test (6MWT)," in which the distance a patient can walk in 6 minutes on a flat surface is measured (in meters) The 6MWT is administered at baseline and 6 months after the start of study treatment. Now suppose that the placebo group had 6-month outcomes that were surprisingly better than at baseline. Describe how each of the 3 mechanisms might be contributing to this improvement.Explanation / Answer
In an experiment, the placebo group had better outcome than the treatment group. This could be due to following reasons,