How Do You Confirm Cystic Fibrosis When Sweat Chloride Test Fails?

Case presentation A 5-year-old girl presented with complaints of constipation, poor weight gain, and a BMI below the third percentile. The patient had a family history of cystic fibrosis (CF). In the assessment of cystic fibrosis, three sweat chloride tests were indeterminate, a CF transmembrane conductance regulator (CFTR) analysis panel was negative, and whole-genome sequence analysis revealed 1CF–causing mutation. What would you do next?

Alternative CFTR functional testing Additional genetic testing Repeat sweat chloride analysis No further testing needed Source: JAMA *This case is from the Editorial Team of Docplexus and is meant for educational purposes only. The correct answer is posted in the comment section below!