Researchers at Northwestern University's Feinberg School of Medicine in Chicago found 78 percent of patients do not fully understand the care and discharge instructions they receive in the emergency department. In addition, 80 percent of the time, patients weren't aware they didn't realize they didn't understand the instructions.

"It's distressing," lead author Dr. Kirsten Engel said in a statement. "It is critical that emergency patients understand their diagnosis, their care, and perhaps most important, their discharge instructions."

Researchers assessed 138 patients and two caretakers from Ann Arbor, Mich., in four categories of comprehension: diagnosis and cause, emergency department care, post-emergency department care and return instructions.

The study, published online in the Annals of Emergency Medicine, found that 51 percent did not understand fully what they were told in two or more categories. More than one-third of the comprehension deficiencies involved patients' understanding of post-emergency department care, while 15 percent involved diagnosis and cause.

Patients can ask staff to repeat or clarify points that remain unclear or ask them to write the instructions.