When a first responder gathers patient information to determine the nature of an illness or injury, this process is called:

The process of gathering patient information to determine the nature of an illness or injury is referred to as patient assessment. This comprehensive evaluation involves different steps, including obtaining vital signs, understanding the patient's medical history, and conducting a physical examination. Effective patient assessment is crucial for first responders, as it helps in identifying the underlying health issues and guides subsequent treatment decisions.

The other terms, while related to patient care, do not encompass the entire process of information gathering as effectively. The secondary survey is a more focused examination that typically occurs after initial stabilization and primary assessment. Nature of illness refers specifically to the diagnosis or condition, while mechanism of injury describes how the injury occurred but does not involve gathering information directly from the patient about their symptoms or history. Thus, patient assessment is the most accurate term for the overall process involved in evaluating a patient's condition.