Final answer:
The nurse violated the principle of role fidelity by diagnosing a patient, which is typically a responsibility of a physician and not within the scope of nursing.
Step-by-step explanation:
The nurse, by diagnosing a medical problem, has violated the principle of role fidelity. This principle prescribes that, in the health care professions, individuals should act within the confines of their roles and the responsibilities that those roles entail. When the nurse takes on the responsibility of diagnosing patients—a task typically reserved for physicians—they are not being faithful to their professional role. Nurses are crucial to the healthcare team, and their role includes a wide range of critical responsibilities, but making diagnoses generally falls outside of their purview.
Role fidelity is a fundamental ethical principle in healthcare that supports trust and predictability in professional relationships and scopes of practice. When healthcare professionals uphold their defined roles, it ensures that patients receive care from individuals who are properly trained and certified for those specific healthcare tasks, thereby upholding the ethical standards of the profession.