How to Use a Subgroup Analysis

You are a physician working 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 information on this topic is derived from a single, blinded trial that randomized trauma patients to tranexamic acid or placebo. The original publication reported that 99% of the enrolled patients were followed up and there was a reduction in all-cause mortality (relative risk [RR], 0.91; 95% CI. 0.85-0.97) with no apparent subgroup effect. A subsequent publication focused on an additional analysis addressing death from bleeding and reported a powerful subgroup effect with a large benefit for patients treated within 3 hours of injury and possible harm if treated 3 or more hours after injury. The committee's mandate is to decide whether tranexamic acid should not be given to patients 3 hours or more after injury. The credibility you place on the subgroup analysis will determine your decision.