Sweat chloride: quantitative patch for collection and measurement

Abstract

Objective: To compare two quantitative pilocarpine iontophoresis tests for sweat chloride.

Design: Simultaneous right and left arm sweat tests were done with the Gibson/Cooke and the CF quantum technologies.

Setting: Sweat tests were performed in a quality controlled cystic fibrosis (CF) sweat test laboratory by an experienced technologist at the University of Minnesota CF Center.

Patients: Patients referred for sweat tests as well as volunteer CF and control subjects (50 CF and 114 'normals') were tested.

Interventions: Standard procedures were used for the Gibson/Cooke test (GCST). The manufacturer of the CF quantum test (CFQT) provided factory standardized materials.

Main outcome measures: Sweat chloride concentration, test time, failed tests, sensitivity, specificity, and cost.

Results: Duplicate test comparing the CFQT and the GCST revealed good comparability (R2 = 0.9434). Sensitivity and specificity of the two methods are comparable at about 94% and 99% respectively. Rate of failed tests was 1% for the CFQT and 15% for the GCST. The CFQT and the GCST are comparable (R2 = 0.9434). Sensitivity (94%) and specificity (99%) are the same for both tests.

Conclusions: The CFQT method is equal in accuracy and reliability to the more labor-intensive and costly GCST. Advantages of the CFQT are: the small sample size required (three to ten mg), decreased operator dependence, simpler to perform, and requires less equipment. It could be used in a clinic setting to diagnose CF in patients with suggestive symptoms.