A 4-month-old infant is brought to the pediatrician by his parents because they’re concerned about his frequent respiratory infections, poor feeding habits, frequent vomiting, and colic. The physician notes that the baby has failed to gain expected weight and recommends that the baby have a sweat test performed to detect possible cystic fibrosis. To prepare the parents for the test, the nurse should explain that（）
A. the baby will need to fast before the test.
B. a sample of blood will be necessary.
C. a low-sodium diet is necessary for 24 hours before the test.
D. a low-intensity, painless electrical current is applied to the skin.
参考答案：D
解析：
Because cystic fibrosis clients have elevated levels of sodium and chloride in their sweat, a sweat test is performed to confirm this disorder. After pilocarpine (a cholinergic medication that induces sweating) is applied to a gauze pad and placed on the arm, a low- intensity, painless electrical current is applied for several minutes. The arm is then washed off, and a filter paper is placed over the site with forceps to collect the sweat. Elevated levels of sodium and chloride are diagnostic of cystic fibrosis. No fasting is necessary before this test and no blood sample is required. A low-sodium diet isn’t required before the test.