Sweat Stimulation and Collection

Critical Issues Associated With Sweat Collection 

The analyst must address several important issues when collecting sweat. These include adequate patient education, using appropriate stimulation and collection systems, preventing evaporation and contamination, collecting a sufficient sample, and minimizing skin reactions. 

Sweat testing is one of the few clinical chemistry tests involving direct patient contact. Patients often have questions about the sweat test that their physicians may not have answered. Patient educational materials on sweat testing have been produced by the CFF in EngHsh and Spanish and include both written and video material. 

Testing procedures should minimize the opportunity for evaporation and contamination of the sweat sample. Detailed instructions on minimizing evaporation and contammation can be found in the NCCLS sweat testing document.  

Specimen Weight and Collection Time To have a valid sweat testing result, determination of and adherence to a minimum sweat weight or volume are critical. The requirement for a minimum amount is physiological, to ensure an appropriate sweat rate and sweat electrolyte concentration. It is independent of the instrumentation used to measure sweat electrolytes. Unfortunately, this is poorly understood, leading to false-positive and false-negative sweat test results, which have a significant implication for patient care. Sweat electrolyte concentration is related to sweat rate. 

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