A quantitative sweat chloride test is required to confirm the diagnosis of CF. This test is referred to as the quantitative pilocarpine iontophoresis test (QPIT). The QPIT involves quantitating the amount of sweat collected and the chloride concentration from either gauze/filter paper pads or Macroduct® coil. Generally, chloride concentration is determined by coulometric titration with a chloridometer. Automated analyzers used for serum or urine chloride may not possess sufficient sensitivity for detecting the lower concentrations of chloride found in sweat. The lower limit of the analytical measurement range for sweat chloride should be less than or equal to 10 mmol/L on unadulterated sweat.
