14 Standardized protocol for ratiometric measurement of b-adrenergic/cholinergic sweating in human sweat glands

Objective Wine et al, (Plos ONE 2013 and 2014) recently published a bioassay for testing CFTR function in vivo. A ratio was computed between CFTR-independent (M-sweat, stimulated by methacholine) and CFTR-dependent (C-sweat, evoked by a b-adrenergic cocktail) sweat secretion rates by multiple individual glands, measured in a series of subjects. Secretion rates were given by changes of volume of sweat drops secreted in an oil layer, including the presence of a water-soluble dye for the C-sweat. Multicenter validation for diagnosis and detection of CFTR function improvement during treatments with drugs targeting the basic defect require a Standardized Operating Procedure (SOP). We have been focusing on developing a simplified method suitable for implementation in clinical multicentric trials, in collaboration with J.W. (Stanford, USA), and on setting up the method in Brussels. Methods The published procedure was adapted because specific concerns were commercial availability of instruments, reproducibility of image analysis and reducing costs. Reference data collection was planned in non-CF subjects, patients with classical or non-classical CF and carriers. Results We aim at automating the analysis procedure originally performed using the ImageJ software. We reproduced the test at the CF Center of Verona, simplified the procedure and acquired images for developing the image analysis software in collaboration with researchers at Politecnico di Milano (Italy). Conclusion Standardization of a protocol for testing CFTR function in vivo that is complementary to sweat tests already available will contribute to multicenter studies as well as to controversial diagnosis.