A sentinel event is best described as:

• A. An expected event
• B. An unexpected occurrence involving death or serious psychological injury that requires immediate investigation
• C. A standard operating procedure
• D. A routine safety drill

Answer: (B)

In patient safety, a sentinel event is an unexpected incident that results in death or serious physical or psychological injury, or the risk thereof. The key point is that the event is not anticipated and has the potential to cause grave harm, triggering an immediate formal investigation to identify system failures and prevent recurrence. This emphasis on urgency and significance is what makes the description the best fit. It isn’t describing an expected outcome, a standard operating procedure, or a routine drill; those do not involve unexpected severe harm or the mandated prompt investigation that defines sentinel events. Examples include events like wrong-site surgery or medication errors leading to serious harm, which prompt rapid review to uncover underlying process flaws.