Final answer:
When a nurse enters the room and starts talking about a patient's clinical details, you should ask them to step out, inform them of the HIPAA violation, and report the incident to the study supervisor.
Step-by-step explanation:
In this situation, there are several actions you should take to ensure patient confidentiality is maintained. First, you should ask the nurse to step out of the room with you to discuss the other patient. This will help prevent any clinical details from being overheard by the current patient. Second, you should inform the nurse that discussing patient information in this manner violates HIPAA rules, which protect patient privacy. Lastly, you should report the incident to the study supervisor so that appropriate actions can be taken to address the violation.