title: Combining risk difference and risk ratio in noninferiority trials of safety.
abstract: Prior to marketing, the long-term safety profile of a new therapy is often uncertain. One recommendation for premarket safety studies is to compare the new therapy to an appropriate control to determine whether the 95% confidence interval of the risk ratio is entirely less than a prespecified threshold (e.g., 1.8). The restriction to the risk ratio, however, has consequences that may not be intended. Risk difference may be a more appropriate measure of risk in this setting when event rates are very low. We propose using a suitable combination of risk ratio and risk difference in demonstrating noninferiority.
authors: Berry Consultants, LLC, Austin, Texas, USA. kristine@berryconsultants.com
authors: Kristine R
authors: KR
authors: Broglio
authors: Jason T
authors: JT
authors: Connor
authors: Scott M
authors: SM
authors: Berry
mesh_terms: D002986:Clinical Trials as Topic / Q000009:adverse effects* / Q000592:standards*; D006801:Humans; D016017:Odds Ratio; D061214:Patient Safety / Q000592:standards*; D012307:Risk Factors