Question 1 of 60

A 4-month-old infant with a positive newborn screen and poor weight gain undergoes a sweat chloride test, which returns at 45 mmol/L on an adequate sample. Which of the following is the most appropriate interpretation and next step?

• A.This is an intermediate result; repeat sweat testing and pursue CFTR mutation analysis (extended genotyping) to establish or exclude the diagnosis
• B.This is diagnostic of cystic fibrosis; no further testing is required
• C.This is a normal result that definitively excludes cystic fibrosis
• D.This result is invalid; only values above 100 mmol/L are interpretable
• E.Immediately start lifelong pancreatic enzyme replacement based on this value alone