Physiology The best indicator of cystic fibrosis is A A positive family history of cystic fibrosis B The presence of digital clubbing C A sweat test with a chloride concentration of 70mEq/L D Bronchiectasis on a chest x-ray 💡 Explanation The best indicator of cystic fibrosis is ✓ Correct Answer: C. A sweat test with a chloride concentration of 70mEq/L