Which sweat test result indicates cystic fibrosis?

Which sweat test result indicates cystic fibrosis?

• A. 25 mmol/L
• B. 40 mmol/L
• C. 55 mmol/L
• D. >60 mmol/L

Answer: (D)

A sweat chloride level greater than 60 mmol/L is diagnostic for cystic fibrosis. The test measures chloride in sweat because CFTR dysfunction causes unusually high chloride loss in sweat. Normal levels are typically below 40 mmol/L, and values in the 40–59 mmol/L range are considered intermediate and may require repeat testing or genetic analysis to confirm CF. Therefore, a result above 60 mmol/L clearly indicates CF.

A sweat chloride level greater than 60 mmol/L is diagnostic for cystic fibrosis. The test measures chloride in sweat because CFTR dysfunction causes unusually high chloride loss in sweat. Normal levels are typically below 40 mmol/L, and values in the 40–59 mmol/L range are considered intermediate and may require repeat testing or genetic analysis to confirm CF. Therefore, a result above 60 mmol/L clearly indicates CF.