An International Randomized Multicenter Comparison of Nasal Potential Difference Techniques

doi:10.1378/chest.10-0179

Chest

Volume 138, Issue 4, October 2010, Pages 919-928

https://doi.org/10.1378/chest.10-0179 Get rights and content

Background

The transepithelial nasal potential difference (NPD) is used to assess cystic fibrosis transmembrane conductance regulator (CFTR) activity. Unreliability, excessive artifacts, and lack of standardization of current testing systems can compromise its use as a diagnostic test and outcome measure for clinical trials.

Methods

To determine whether a nonperfusing (agar gel) nasal catheter for NPD measurement is more reliable and less susceptible to artifacts than a continuously perfusing nasal catheter, we performed a multicenter, randomized, crossover trial comparing a standardized NPD protocol using an agar nasal catheter with the same protocol using a continuously perfusing catheter. The data capture technique was identical in both protocols. A total of 26 normal adult subjects underwent NPD testing at six different centers.

Results

Artifact frequency was reduced by 75% (P < .001), and duration was less pronounced using the agar catheter. The measurement of sodium conductance was similar between the two catheter methods, but the agar catheter demonstrated significantly greater CFTR-dependent hyperpolarization, because δ zero Cl- + isoproterenol measurements were significantly more hyperpolarized with the agar catheter (224.2 ± 12.9 mV with agar vs 18.2 ± 9.1 mV with perfusion, P < .05).

Conclusions

The agar nasal catheter approach demonstrates superior reliability compared with the perfusion nasal catheter method for measurement of NPD. This nonperfusion catheter method should be considered for adoption as a standardized protocol to monitor CFTR activity in clinical trials.

Section snippets

Study Design

Each institution obtained approval for the NPD comparison in human subjects from their respective institutional review board or ethics committee, and written informed consent was obtained from all study subjects. The University of Alabama at Birmingham's institutional review board approved the central analysis of the data. The subjects then underwent NPD testing using the other methodology at least 1 day later, a period sufficient to wash out the effects of amiloride and isoproterenol. Normal

Results

A total of 26 subjects from six centers underwent randomization and completed the protocol. The mean age of the subjects was 39 (±12) years, and 78% were women (Table 1). Representative tracings are provided in Figure 2 and include examples of transient excursions and sustained breaks (Fig 2A). Comparison of tracings obtained using the agar catheter method with those obtained using the perfusion method in the same nostril of the same subject revealed that tracings using the agar catheter were

Discussion

To our knowledge, this study represents the first rigorous, randomized, controlled, multicenter comparison of methods for measurement of the NPD. Our results demonstrate that an agar catheter yields significantly enhanced data quality compared with the perfusion catheter. The improvements in signal quality and tracing stability address important limitations of the NPD assay that have adversely affected reproducibility in previous studies.19, 24 These findings were observed both in centers with

Conclusions

A number of CFTR modulators that can be used potentially to improve the underlying defect in CFTR activity are being evaluated in clinical testing, including potentiators of surface-localized CFTR,¹¹ correctors of ΔF508 CFTR processing (clinicaltrials.gov, NCT00865904), and suppressors of premature termination codons.8, 9, 10, 23 The development of each of these approaches has used proof-of-concept studies based on NPD measurements. Given the importance of this biomarker in the measurement of

Acknowledgments

Author contributions: Dr Rowe has access to all data and takes full responsibility for data analysis and accuracy.

Dr Solomon: contributed to the development and pilot testing of the agar catheter, the performance of NPDs, the supervision of statistical analysis, and the writing of the manuscript, and was one of the overall principal investigators.

Dr Konstan: contributed as principal investigator at his site.

Dr Wilschanski: contributed as principal investigator at his site.

Dr Billings:

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Cited by (49)

Riociguat for the treatment of Phe508del homozygous adults with cystic fibrosis
2021, Journal of Cystic Fibrosis
Citation Excerpt :
Safety assessments included laboratory measurements and monitoring of adverse events (AEs) according to Medical Dictionary for Regulatory Activities (MedDRA) version 19.1, with symptomatic hypotension and hemoptysis defined as AEs of special interest. Nasal potential difference measurements were performed according to the joint Cystic Fibrosis Foundation-European Cystic Fibrosis Society standard operating procedure, with total CFTR-dependent chloride secretion as a measure of CFTR activity [16]. LCI2.5 was measured from nitrogen multiple breath washouts with the Exhalyzer D (Ecomedics, Duernten, Switzerland).
Riociguat is a first-in-class soluble guanylate cyclase stimulator for which preclinical data suggested improvements in cystic fibrosis transmembrane conductance regulator (CFTR) function.
This international, multicenter, two-part, Phase II study of riociguat enrolled adults with cystic fibrosis (CF) homozygous for Phe508del CFTR. Part 1 was a 28-day, randomized, double-blind, placebo-controlled study in participants not receiving CFTR modulator therapy. Twenty-one participants were randomized 1:2 to placebo or oral riociguat (0.5 mg three times daily [tid] for 14 days, increased to 1.0 mg tid for the subsequent 14 days). The primary and secondary efficacy endpoints were change in sweat chloride concentration and percent predicted forced expiratory volume in 1 second (ppFEV₁), respectively, from baseline to Day 14 and Day 28 with riociguat compared with placebo.
Riociguat did not alter CFTR activity (change in sweat chloride) or lung function (change in ppFEV₁) at doses up to 1.0 mg tid after 28 days. The most common drug-related adverse event (AE) was headache occurring in three participants (21%); serious AEs occurred in one participant receiving riociguat (7%) and one participant receiving placebo (14%). This safety profile was consistent with the underlying disease and the known safety of riociguat for its approved indications.
The Rio-CF study was terminated due to lack of efficacy and the changing landscape of CF therapeutic development. The current study⁠, within its limits of a small sample size, did not provide evidence that riociguat could be a valid treatment option for CF.
Clinical trial registration number: NCT02170025.
Insights into the variability of nasal potential difference, a biomarker of CFTR activity
2020, Journal of Cystic Fibrosis
Nasal potential difference (NPD) is used to evaluate CFTR function in vivo. We aimed to evaluate the intrasubject and intersubject variability of NPD measurements.
We reviewed NPD tracings of 116 patients with CF enrolled in the placebo arm of a multicenter study. Patients carried at least one nonsense mutation and underwent repeated NPD tests every 16 weeks. NPD parameters included basal potential difference (basal PD), inhibition of sodium absorption by amiloride (Δ Amiloride), chloride (Cl⁻) transport in response to a Cl⁻-free solution (Δ Low Cl⁻), isoproterenol (Δ Isoproterenol), the sum of Δ Low Cl⁻ and Δ Isoproterenol (Δ Low Cl⁻-Isoproterenol) and ATP (Δ ATP).
Basal PD and Δ Amiloride displayed the highest variabilities, mainly stemming from intercenter and intrasubject effect. Δ Low Cl⁻, Δ Isoproterenol and Δ Low Cl⁻-Isoproterenol demonstrated a large intrasubject variability but a smaller intersubject variability. The intrasubject measurement variability for Δ Low Cl⁻-Isoproterenol, was within ± 7.2 mV with 95% probability. It was greater in patients reporting ongoing pulmonary exacerbations.
The large intercenter variability of basal PD and Δ Amiloride highlights the operator-dependent aspect of these measurements. A difference greater than 7.2 mV in Δ Low Cl⁻-Isoproterenol in a given patient on CFTR modulator can be attributed, with 95% probability, to a treatment effect rather than to the variability inherent in the measurement.
Nanomedicine for Cystic Fibrosis
2019, SLAS Technology
Cystic fibrosis is a genetic disease affecting more than 70,000 people worldwide. Caused by a mutation in the CFTR gene, cystic fibrosis can result in difficulty breathing, widespread bacterial infections, edema, malnutrition, pancreatitis, and death. Current drug-based treatments struggle to reach the site of action due to the thick mucus, and only manage symptoms such as blocked airways, lung infections, and limited ability to digest food. Nanotechnology opens up possibilities for improved treatment strategies by focusing on drug penetration through the mucus lining, eliminating resulting bacterial infections, and targeting the underlying genetic cause of the disease. In this review, we present recent nanoparticle developments for cystic fibrosis, challenges in nanomedicine therapeutics, and future research directions in gene editing and nonviral vectors for gene delivery.
49 - Genetics and Pathophysiology of Cystic Fibrosis
2019, Kendig's Disorders of the Respiratory Tract in Children
Our understanding of the role of disease-causing variants in CFTR has culminated in two new variant-specific CFTR modulator therapies approved by the US FDA. These modulators target defects in CFTR biogenesis and in channel gating. Clinical trials are directed to improving the efficacy of these first-generation molecules. However, other CFTR variants that lead to nonsense-mediated decay, aberrant splicing, and reduced gene expression are refractory to CFTR modulators and will require new therapeutic approaches. To this end, new CF animal models are yielding key insights into tissue-specific disease mechanisms, such as impaired mucociliary clearance and pancreatic dysfunction. Although infection and inflammation remain challenging to treat, progress in targeting CFTR directly will result in individuals with CF living longer. To maximize life span, earlier interventions, soon after diagnosis, are needed. Finally, the advances in precision medicine for CF may benefit more common disorders such as COPD and pancreatitis where CFTR dysfunction contributes to pathophysiology.
Diagnosis and Presentation of Cystic Fibrosis
2019, Kendig's Disorders of the Respiratory Tract in Children
Most children with cystic fibrosis (CF) in current times are likely to be picked up through newborn screening programs and confirmed by the finding of two CF-causing mutations and a positive sweat test. They may be clinically well at the time of detection but likely to develop CF symptoms in time and will require prompt, effective intervention. Some children will be missed through the screening program, and pediatricians must remain vigilant to this possibility. No racial group is exempt from the disorder, and children of ethnic minorities or mixed heritage are at greatest risk of a delayed or a missed diagnosis. The clinical features of recurrent chest infections, malabsorption with pancreatic insufficiency in many but not all, salt losing syndromes, or an infant presenting with meconium ileus or rectal prolapse requires investigation. Recent consensus statements have provided useful guidance on the diagnostic criteria for CF.
One of the unintended consequences of CF screening programs has been the detection of children in whom the full diagnostic criteria are not met. This group is referred to by the acronym CFSPID/CRMS. These children may require monitoring over time and possibly reevaluation depending on their clinical course. The range of clinical features for individuals with 2 CFTR mutations is wide and some may not develop symptoms at all or have an incomplete phenotype—often with single organ disease. Currently, such individuals often present clinically as adults and are not necessarily given the full cystic fibrosis label but considered to have a “CFTR related disorder.”
A multiple reader scoring system for Nasal Potential Difference parameters
2017, Journal of Cystic Fibrosis
Citation Excerpt :
NPD is a key outcome measure for experimental therapeutics addressing the CF ion transport abnormality, including modulators of CFTR function [9] Ivacaftor [10] and Lumacaftor [11] and other CFTR modulators [12,13] in development; CFTR-gene directed treatments [14–18]; and inhibitors of ENaC [19–22]. While improved NPD methods now allow for the use of NPD in multi-center trials with electronic data capture and blinded interpretation that have improved its reliability [23,24] and has been agreed upon by the US TDN and EU CTN, there has not yet been a proposed standardized interpretation protocol to ensure uniform interpretation within clinical trials. Furthermore, a standardized scoring system allows for a multiple reader approach to adjudicate the inclusion of questionable tracings, which could improve the performance of NPD, particularly for smaller early phase and proof-of-concept clinical trials.
Nasal Potential Difference (NPD) is a biomarker of CFTR activity used to diagnose CF and monitor experimental therapies. Limited studies have been performed to assess agreement between expert readers of NPD interpretation using a scoring algorithm.
We developed a standardized scoring algorithm for “interpretability” and “confidence” for PD (potential difference) measures, and sought to determine the degree of agreement on NPD parameters between trained readers.
There was excellent agreement for interpretability between NPD readers for CF and fair agreement for normal tracings but slight agreement of interpretability in indeterminate tracings. Amongst interpretable tracings, excellent correlation of mean scores for Ringer's Baseline PD, Δ_amiloride, and Δ_{Cl-free + Isoproterenol} was observed. There was slight agreement regarding confidence of the interpretable PD tracings, resulting in divergence of the Ringers and Δ_amiloride, and ΔCl_{-free + Isoproterenol} PDs between “high” and “low” confidence CF tracings.
A multi-reader process with adjudication is important for scoring NPDs for diagnosis and in monitoring of CF clinical trials.

View all citing articles on Scopus

Funding/Support: This research was funded by the US National Institutes of Health [Grants 1K23DK075788-01 and 1R03DK084110-01 (to Dr Rowe) and Grant 1P30DK072482-01A1 (to Eric J. Sorscher)] and the Cystic Fibrosis Foundation [Grants CLANCY05Y2 (Drs Clancy and Rowe) and RAMSEY03Y0 (to the Therapeutics Development Network Coordinating Center)].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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Chest

Original ResearchCystic FibrosisAn International Randomized Multicenter Comparison of Nasal Potential Difference Techniques

Background

Methods

Results

Conclusions

Section snippets

Study Design

Results

Discussion

Conclusions

Acknowledgments

J Cyst Fibros

J Pediatr

Mol Ther

Lancet

Chest

Cystic fibrosis

N Engl J Med

Increased bioelectric potential difference across respiratory epithelia in cystic fibrosis

N Engl J Med

Relative ion permeability of normal and cystic fibrosis nasal epithelium

J Clin Invest

Phenotypic characterisation of patients with intermediate sweat chloride values: towards validation of the European diagnostic algorithm for cystic fibrosis

Thorax

Gentamicin-induced correction of CFTR function in patients with cystic fibrosis and CFTR stop mutations

N Engl J Med

No detectable improvements in cystic fibrosis transmembrane conductance regulator by nasal aminoglycosides in patients with cystic fibrosis with stop mutations

Am J Respir Cell Mol Biol

NPD evaluation of ion transport with a CFTR potentiator

Pediatric Pulm Supp

Original Research
Cystic Fibrosis
An International Randomized Multicenter Comparison of Nasal Potential Difference Techniques