How to Use a Subgroup Analysis

You are a physicianworking at a regional trauma center. Your unit's committee,which is responsible for standardization of care, is considering using tranexamic acid to treat trauma patients arriving 3 hours after injury. Almost all the informationon this topic is derived fromasingle,blindedtrial that randomizedtraumapatients totranexamic acid or placebo. Theoriginal publication reported that99%of the enrolled patients were followed up and there was a reduction inall-causemortality (relative risk [RR],0.91;95%CI.0.85-0.97)with noapparent subgroupeffect. A subsequentpublication focusedon an additional analysis addressing death from bleeding and reported a powerful subgroup effect with a large benefit for patients treatedwithin3hoursof injuryandpossibleharmif treated3ormore hours after injury. The committee's mandate is to decide whether tranexamic acid should not be given to patients 3 hours ormore after injury. The credibility youplaceon the subgroupanalysiswill determine your decision.