Sweat Testing: Specimen Collection and Quantitative Chloride Analysis
|Publication Date:||1 February 2019|
This guideline provides recommendations for sweat stimulation by pilocarpine iontophoresis (specific precautions are noted), sweat collection in filter paper or gauze (see Appendix A) or in a commercial sweat collector using coiled tubing (see Appendix B), and quantitative chloride measurement. The procedure for sweat chloride (chloride ion [Cl−]) determination using coulometric titration is described. Sweat conductivity screening methods are also mentioned. Sweat chloride test results evaluation, including reference intervals and diagnostic criteria, is described, with an emphasis on sweat chloride testing for newborn cystic fibrosis (CF) screening. Validation studies and QA techniques are discussed, along with analytical and biological error sources.
The intended users of this guideline are laboratory and clinical personnel responsible for collecting sweat specimens, measuring sweat chloride, and evaluating and reporting sweat test results.
Procedures for gauze or filter paper collection and analysis are located in Appendix A because many of these systems are no longer manufactured. Other methods for measuring sweat electrolytes after pilocarpine iontophoresis exist but are not included in this guideline. Some of these methods have significant documented analytical problems, as well as limited diagnostic application.2,4-7