In contrast to practically every other specialty of nursing, in which a patient arrives with a diagnosis applied by a physician and the nurse must manage the patient's care according to that diagnosis, emergency nurses work with patients in whom a diagnosis has not yet been made and the cause of the problem is not known. Emergency nurses frequently contact patients in the emergency department before the patient sees a physician. In this situation, the nurse must be skilled at rapid, accurate physical examination, early recognition of life-threatening illness or injury, the use of advanced monitoring and treatment equipment, and in some cases, the ordering of testing and medication according to "advance treatment guidelines" or "standing orders" set out by the hospital's emergency physician staff. Emergency nurses most frequently are employed in hospital emergency departments, though they may also work in free-standing urgent care clinics. Behavioral health patients have become an increasing concern for emergency nurses