Open Journal of Respiratory Diseases, 2012, 2, 43-56 http://dx.doi.org/10.4236/ojrd.2012.22007 Published Online May 2012 (http://www.SciRP.org/journal/ojrd) Comparative Variability of Nasal Potential Difference Measurements in Human and Mice Anissa Leonard 1,2* , Bob Lubamba 2* , Barbara Dhooghe 2 , Sabrina Noel 2 , Pierre Wallemacq 2 , Patrick Lebecque 1 , Teresinha Leal 1,2# 1 Pediatric Pulmonology & Cystic Fibrosis Unit, St Luc University Hospital, Brussels, Belgium 2 Louvain Centre for Toxicology and Applied Pharmacology, Institut de Recherche Clinique et Expérimentale, Université Catholique de Louvain, Brussels, Belgium Email: # teresinha.leal@uclouvain.be Received February 21, 2012; revised March 20, 2012; accepted April 25, 2012 ABSTRACT Background: Nasal potential difference (NPD) test has long been used to assist in the diagnosis of Cystic Fibrosis (CF) and more recently as an outcome measure in clinical trials of new CF therapies. This test has also been adapted to the mouse nose. Objectives: We aimed at evaluating variability of the NPD measurements in CF patients displaying two severe CFTR mutations and in sex-matched healthy controls. NPD recorded from F508del-CF and normal wild-type mice were also compared. Methods and Results: In each setting, tests were performed by a single qualified operator. In the clinical setting, the latest standardized operation protocol of the CF foundation was followed. A total of 80 trac- ings were obtained from 10 patients (23.2 y; range 14 to 32) and 10 healthy subjects (34 y; range 24 to 53), each tested twice, in both nostrils. Two CF and two controls were excluded from the statistical data analysis due to the presence of a single non interpretable NPD tracing (4/80, 5%). To achieve equal sample size, tests were obtained from 8 CF mice and normal wild-type. Comprehensive multivariate analysis of paired data showed a good reproducibility of NPD pa- rameters in the clinical and the preclinical setting; lower variability was observed in mice. However, 95% repeatability limits of NPD parameters were large indicating a large measurement error, poor precision and low within-subject re- peatability. In both settings, chloride secretion was shown to be the most reproducible and repeatable parameter. Con- clusion: In human as in mice, NPD showed good reproducibility but limited within-subject repeatability. Keywords: Animal Models; CFTR; Cystic Fibrosis; Nasal Potential Difference 1. Introduction Electrical potential difference (PD) across the mucous nasal epithelia has been used for more than two decades to assess cystic fibrosis (CF) transmembrane conductance regulator (CFTR) activity and to assist in the diagnosis of CF [1]. As a multiphase test performed under continuous perfusion [2,3], nasal PD allows functional dissection of CFTR and epithelial sodium channel (ENaC) at the nasal mucosa, explored as a representative sample of distal airways [1]. Implementation of the nasal PD test into CF centers around the world has been challenging as the technique is delicate and it requires dedicated equipment and supplies and trained skilled operators. To explore the presence in CF of ion transport abnormalities, CF research teams had to develop inventive in-house setups of the test. As a result, operating protocols have critically diverged among CF centers. The nasal PD test has also proved to be helpful for the differential diagnosis of atypical CF and CFTRopathies other than CF [4,5]. More recently, the test has been used as an outcome measure in clinical trials of new CF thera- pies to assess therapeutic modulation of the basic CFTR defect [6-16]. Therefore, an urgent need of standardizing the test has emerged. Substantial efforts have been devoted by the CF Foundation Therapeutics-Therapeutics Devel- opment Network (CFFT-TDN) and by the Clinical Trial Network of the European Cystic Fibrosis Society (ECFS- CTN) to perfect a standardized operating protocol (SOP) to be adopted by CF centers worldwide. Adoption of a nasal PD SOP is expected to reduce real-time recording artifacts, to improve quality of data [17] and also to mini- mize inter-site variability. Studies on variability of the test under these optimized conditions are missing. The nasal PD test has been adapted to the mouse nose [18] which has allowed investigating the potential of new CF therapies in preclinical settings [19-21]. Translation of data into clinical practice deals with obvious pheno- typic differences between mouse and human CF disease * Equal contributors. # Corresponding author. Copyright © 2012 SciRes. OJRD