Due to the defective CFTR protein, chloride and sodium are not reabsorbed by the epithelial cells as the sweat moves up the ducts, which results in an increase in ions present in sweat (see Figure 2 below). It is important to note that patients with CF do not produce increased volumes of sweat, rather the sweat contains increased concentrations of sodium and chloride. The increased concentration of chloride in sweat is the basis for the diagnosis of CF. Figure 2
Image is courtesy of CFTR. Info website. Available at: http:="" www.cftr. info="" about-cf="" role-of-ctfr-in-cf="" pathophysiology-of-cf="" sweat-gland="" how-cf-modifies-sweat-chloride-levels-at-the-cellular-level. Accessed January 26, 2015.