Final answer:
For a pulmonary function test, the patient should remove restrictive clothing such as a suit and tie, and potentially put on a gown to avoid interference with the test results.
Step-by-step explanation:
When preparing a patient for a pulmonary function test, it is important for the medical assistant to ensure that the patient's clothing does not restrict breathing. Therefore, the assistant should instruct the patient to remove the suit and tie. These items of clothing can constrict the neck and chest, potentially affecting the test results. It may also be beneficial for the patient to put on a gown provided by the clinic to ensure comfort and ease of movement during the test.