Cystic fibrosis (CF) remains one of the most prevalent, life-shortening genetic diseases in the Caucasian population. CF has remained under-diagnosed in many developing countries because its clinical characteristics are similar to respiratory and gastrointestinal issues associated with malnourishment, failure to thrive and high infant mortality. The CF phenotype is characterized by complex, multi organ involvement, analyzed in context of its various clinical components such as, pulmonary disease, pancreatic exocrine dysfunction or sweat chloride abnormality among others. Clinical consequences of the CFTR defect are site-specific and range from severe (lungs, pancreas, male reproductive tract) to mild (intestine) to asymptomatic (sweat glands). CF is diagnosed when an individual has both: at least one clinical presentation of the disease, and evidence of CFTR dysfunction. Evidence of CFTR dysfunction must be demonstrated either by: An elevated chloride concentration in sweat (≥ 60 mmol/L) in at least two independent measurements, and/or The demonstration of at least two cystic-fibrosis-causing CFTR mutations intrans, i.e., one mutation on each of the two chromosomes, and/or The demonstration of a characteristic type of CFTR dysfunction with nasal potential difference measurement (NPD) or intestinal short-circuit current measurement (ICM).