Final answer:
A nurse should consider hospitalization for an anorexia nervosa patient with decreased intake of phosphate-containing foods, as it may indicate serious hypophosphatemia.
Step-by-step explanation:
When reviewing the medical record of a patient with anorexia nervosa, a nurse should recognize that a decreased intake of phosphate-containing foods may be an indication that the patient requires hospitalization. This could lead to hypophosphatemia, an abnormally low level of phosphate in the blood, which is a serious condition that often develops in individuals with anorexia nervosa due to malnutrition and can cause significant organ dysfunction.