Sweat chloride in cystic fibrosis

Robbins basic pathology 9th edition page no 226, An increase in sweat chloride concentration is a major criteria for the diagnosis of cystic fibrosis. Page no 223: the primary defect in cystic fibrosis is abnormal function of an epithelium chloride channel protien encoded by the cystic fibrosis transmembrane conductance regulator gene at chromosome locus. Thus the epithelium membrane become impermeable to chloride channels