Non-inferiority testing for risk ratio, odds ratio and number needed to treat in three-arm trial

• Published in: Computational statistics & data analysis Vol. 132; pp. 70 - 83
• Main Authors: Chowdhury, Shrabanti, Tiwari, Ram C., Ghosh, Samiran
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2019
• Subjects: Assay sensitivity; Binary outcome; clinical trials; Fraction margin; guidelines; Non-inferiority margin; odds ratio; Odds/risk ratio/NNT; placebos; relative risk; Three-arm trial; Fraction margin; Assay sensitivity; Odds/risk ratio/NNT; Non-inferiority margin; Three-arm trial; Binary outcome; Assay Sensitivity; Binary Outcome; Three-arm Trial; Fraction Margin; Odds/Risk Ratio/NNT; Non-inferiority Margin
• ISSN: 0167-9473; 1872-7352
• DOI: 10.1016/j.csda.2018.08.018

Three-arm non-inferiority (NI) trial including the experimental treatment, an active reference treatment, and a placebo where the outcome of interest is binary are considered. While the risk difference (RD) is the most common and well explored functional form for testing efficacy (or effectiveness), however, recent FDA guideline suggested measures such as relative risk (RR), odds ratio (OR), number needed to treat (NNT) among others, on the basis of which NI can be claimed for binary outcome. Albeit, developing test based on these different functions of binary outcome are challenging. This is because the construction and interpretation of NI margin for such functions are non-trivial extensions of RD based approach. A Frequentist test based on traditional fraction margin approach for RR, OR and NNT are proposed first. Furthermore a conditional testing approach is developed by incorporating assay sensitivity (AS) condition directly into NI testing. A detailed discussion of sample size/power calculation are also put forward which could be readily used while designing such trials in practice. A clinical trial data is reanalyzed to demonstrate the presented approach.