- Subjects with CF as diagnosed by one of the following: documented sweat chloride >= 60 mEq/L by quantitative pilocarpine iontophoresis test, or documented sweat sodium >= 60 mmol/L, or 2 well characterized genetic mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, or abnormal nasal potential difference with accompanying symptoms characteristic of CF