Relationship between sweat chloride and pulmonary function in healthy young adults - a single-center, pilot study

The role of Cystic Fibrosis Transmembrane Conductance regulator (CFTR) dysfunction in non-cystic fibrosis lung diseases, including COPD, is not well understood. The objective of this study was to assess the prevalence of intermediate sweat chloride levels, 30-59 mmol/L, in healthy young adults and the relationship between sweat chloride and pulmonary function.

Healthy volunteers >18 years of age were enrolled in this single center, prospective, cross-sectional pilot study. Sweat chloride testing was performed by pilocarpine iontophoresis. Study participants completed the ATS-DLD LHS-III modified general respiratory symptom questionnaire, spirometry pre- and post-inhaled bronchodilator, and Lung Clearance Index.

93 subjects were enrolled. 1 subject withdrew and 2 had insufficient sweat volumes collected. Median (IQR) age was 27 years (25, 33) and 40 % were male. Median (IQR) sweat chloride was 21 mmol/L (12, 29). 25/90 subjects (28 %) had intermediate sweat chloride values, median 37 (33, 40) mmol/L. 60 % of individuals with intermediate sweat chloride values were male as compared to 34 % of individuals with normal sweat chloride values, p < 0.001. Median FEV₁ (% predicted) was 100 (90, 109), FEV₁/FVC 0.83 (0.81, 0.86), and LCI was 6.01 (5.38, 6.98). There were no differences in pulmonary function between those with normal and intermediate sweat chloride values.

A significant number of healthy young adults have intermediate sweat chloride levels, but no differences in spirometry and LCI were found. Larger studies, including genetic analyses, are needed to determine if mild CFTR dysfunction impacts respiratory health, especially in older individuals with respiratory co-morbidities.