Abstract
Non-inferiority randomized clinical trials are indicated when it is intended to prove that an experimental group is not inferior to a control group by more than a margin of non-inferiority. However, this type of study differs from traditional randomized clinical trials (superiority studies) because they have particularities that impact on the formulation of hypothesis to be tested, experimental design (non-inferiority margin determination, adapted sample size calculation, sensitivity of the study and data final analysis) and also on the presentation of data when writing the manuscript. Therefore, this article aims to present and discuss the particularities of non-inferiority clinical studies, since these requirements are fundamental to guarantee the validity of the conclusions of this type of study.
Highlights
IntroductionDeclaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript
Declaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript.Submitted: Sep 2, 2019 Accepted for publication: Sep 22, 2019 Last revision: June 8, 2020Randomized clinical trials (RTC) are on the second to last step of the evidence-based pyramid
The non-inferiority margin quantifies the maximum loss of clinically acceptable efficacy so that the treatment under study can be declared non-inferior to the control.[5]
Summary
Declaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript. For a standard protocol (positive control) to be replaced by a new one, the experimental group does not necessarily have to be superior to control and in this case non-inferiority clinical trials gain importance. The non-inferiority margin quantifies the maximum loss of clinically acceptable efficacy so that the treatment under study (experimental group) can be declared non-inferior to the control.[5] For a study of this nature, it is not overstatement to say that this is the most important factor to be defined. The first, known as the fixed margin method, uses a value ranging from 50 to 75% of the difference between the values found in control and placebo.[2,3,4,5] The second method, advocated by the FDA, uses 50% of the lower limit of the 95% confidence interval of the difference between the values found in the control and in the placebo groups.[2,3,4,5,6] Regardless of the chosen method, it is essential that the authors report the strategy used to obtain the non-inferiority margin and the value resulted from the calculations, since it will guide all the conclusions of the study
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