A 26 year old caucasian male comes to the physician because of severe productive cough for the past two months. He also complains of occational blood in sputum, and dyspnea for the last three weeks. His past medical history is significant for otitis media. two episodes of pneumonia, and sinusitis. He and his wife were recently worked up for infertility. Physical examination shows crackles in the left upper lobe. Chest X-ray shows dialed and thickened airways and irrigular peripheral opacitis in the left upper lobe.
Which of the following is the most appropriate test to make the diagnosis of his condition?
a) Sweat chloride test.
b) DNA studies.
c) Pulmonary function tests.
d) Semen analysis.
e) Bronchoscopy
