Allocation bias can have a significant effect on cardiovascular treatment findings, according to an analysis that explored cases of conflicting results between randomized, controlled trials and registry studies. RCTs have consistently favored primary angioplasty in STEMI over fibrinolysis, while registry studies tend to find equivalent survival for both approaches. The new research found that just a few high-risk patients masked the survival benefit of percutaneous coronary intervention. "Once this allocation bias is accounted for, registries predict that primary PCI has 22% lower long-term mortality than fibrinolysis," said Dr. Sayan Sen of London's St. Mary's Hospital.

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