Clinical trials are experimental studies — the researcher performs an intervention — conducted in humans. In therapeutic studies, including surgical ones, they carry the highest strength of evidence.
The design of a randomized controlled trial: the draw distributes known and unknown factors equally between groups.
Compares two or more therapies — there is a control group.
Participants are assigned to each group at random.
Neither participants nor researchers know who is in which group.
Clinical trials also serve prophylactic studies — interventions to prevent disease. The classic example is vaccines compared with placebo; in digestive surgery, a trial comparing fundoplication vs. PPI for cancer prevention in Barrett’s esophagus follows the same logic.
No. The control may be standard treatment; placebo is used when no established therapy exists and it is ethically acceptable.
Analyzing each patient in the group they were randomized to, even if they did not complete treatment — it preserves the benefit of randomization.
Yes — and ABCD publishes several. Blinding is harder, but objective outcomes and blinded assessors reduce bias.
Written by Francisco Tustumi, digestive system surgeon (FMUSP), associate editor of ABCD.
Developed by Surya MKT