The Evaluation of Effectiveness, or How Do We Know Whether a Treatment Works in Real Life? Part 2

Abstract

In our previous article (Schindler TM, Bridge H. The evaluation of efficacy, or how do we know whether a treatment works? Part 1. AMWA J. 2020;35(2):82-86), we described how randomized clinical trials (RCTs) determine efficacy of a treatment. Efficacy is generally understood as the ability of a drug or other intervention to reliably produce a positive effect in patients with a defined disease under controlled conditions. In other words, clinical trials are good tools to evaluate efficacy. Clinical trials provide a well-controlled framework that is characterized by the following:

• Selecting participants according to clearly defined eligibility criteria
• Randomly allocating participants to treatment groups
• Concealing study treatments to participants and study doctors (blinding)
• Clearly defining endpoint measures before study start

Provided a drug consistently demonstrates efficacy in several clinical studies and appears safe, regulators will approve it and permit its marketing for the treatment of a disease. However, once a drug is on the market, it will be used for the entire spectrum of patients and under circumstances that might not have been tested in the clinical studies. For example, the new drug will be used in patients who have several comorbidities in addition to the approved indication. The evaluation of a drug’s effects under everyday conditions is called effectiveness research.