Which test can confirm cystic fibrosis by identifying mutations in the CFTR gene?

• A. Newborn screening by IRT
• B. Sweat chloride test (>60)
• C. Genetic testing for CFTR mutation
• D. Chest X-ray

Answer: (C)

Cystic fibrosis is caused by mutations in the CFTR gene, so confirming the diagnosis means showing the actual genetic change. Genetic testing for CFTR mutation directly analyzes the CFTR gene to identify pathogenic variants, providing definitive confirmation that CF is present.

The sweat chloride test measures the functional consequence of CFTR dysfunction by testing chloride in sweat. A high value supports CF but does not identify the gene mutation itself, so it isn’t a genetic confirmation. Newborn screening flags risk by detecting elevated IRT, but it is a screening step, not a diagnostic confirmation. Chest X-ray can reveal lung changes but cannot prove CF at the genetic level.

Therefore, testing that identifies CFTR mutations is the best answer.