Which sign most clearly indicates a transfusion reaction?

• A. Temperature change and tachycardia
• B. Weight gain
• C. Increased appetite
• D. Improved mental status

Answer: (A)

The main idea is that an acute transfusion reaction shows up in vital signs changes right during or shortly after the transfusion. The body’s immune and inflammatory responses to the transfused blood often trigger a fever and a faster heart rate as it reacts to the new blood. Among the options, the combination of a temperature change with tachycardia best matches that immediate, systemic response you’d expect with a transfusion reaction. The other signs—weight gain, increased appetite, or improved mental status—don't reflect the typical acute reaction to transfused blood. So the temperature change together with tachycardia is the clearest indicator.