Document resource
Xu and colleagues quantify the impact of retracted clinical trials on systematic reviews and clinical practice guidelines.1 They found that removing retracted trials altered statistical significance in 16% of meta-analyses and reversed effect direction in 8.4%, with evidence from these distorted systematic reviews cited in 157 clinical practice guidelines. These findings show how flawed data propagate through a “contamination chain” in the biomedical evidence ecosystem. They also highlight a critical gap: the need to tackle contamination beyond formally retracted studies, as retractions are only the tip of a much larger iceberg threatening evidence integrity.