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J Cyst Fibros. 2019 Jul 19. pii: S1569-1993(19)30822-7. doi: 10.1016/j.jcf.2019.07.001. [Epub ahead of print]

Nasal potential difference in suspected cystic fibrosis patients with 5T polymorphism.

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Department of Pulmonology, University Medical Center Utrecht, Postbus 85500, 3508, GA, Utrecht, the Netherlands. Electronic address:
Pediatric Gastroenterology Unit and Cystic Fibrosis Center, Hadassah-Hebrew University Medical Center, Kiryat Hadassah, POB 12000, Jerusalem 91120, Israel.
CF Center, Pediatric Pulmonology and Immunology, Charité Universitätsmedizin, Charitépl. 1, 10117 Berlin, Germany.
Department of Cystic Fibrosis, Royal Brompton Hospital and Imperial College, Sydney Street, SW3 6NP London, United Kingdom.
Department of Pediatric Pneumology, UZ Brussel, Laarbeeklaan 101, B-1090 Brussels, Belgium.
Cystic Fibrosis Centre, Azienda Ospedaliera Universitaria Integrata. Piazzale Aristide Stefani 1, 37126 Verona, Italy.
Department of Pediatric Pulmonology, University Hospital Leuven, Herestraat 49, 3000 Leuven, Belgium.
Louvain Centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, Place de l'Université 1, B-1348 Louvain-la-Neuve, Brussels, Belgium.
CF Center and Clinical Research Group, Department of Pediatric Pneumology and Neonatology, OE 6710, Medical School Hannover, Carl-Neuberg-Straße 1, 30625 Hannover, Germany.
Department of Pulmonology, University Medical Center Utrecht, Postbus 85500, 3508, GA, Utrecht, the Netherlands.



5T polymorphism is a CFTR mutation with unclear clinical consequences: the phenotype varies from healthy individuals to Cystic Fibrosis (CF). The aim of this study was to evaluate if nasal potential difference (NPD) and sweat testing correlate with symptoms and CF diagnosis in 5T patients.


86 patients with 5T who had undergone NPD measurement, were included (6 homozygous (5T/5T), 41 with a PI-CF causing mutation in trans (5T/PI-CF), 11 with a PS-CF causing mutation in trans (5T/PS-CF) and 28 without a known mutation in trans (5T/?). Data including age, phenotype, sweat chloride and follow up were collected.


33% of the 5T/5T patients had abnormal NPD results, compared to 70% in 5T/PI-CF; 33% in 5T/PS-CF and 29% in 5T/?. The percentage of high or borderline sweat chloride was highest in 5T/PI-CF, and 5T/?, compared to 5T/5T and 5T/PS-CF (91, 96, 80, and 63%, respectively). TGm (number of TG repeats in intron 8) analysis was performed in 21 5T/PI-CF patients. TG11 was associated with lower sweat chloride, lower percentage of abnormal NPD and less progression of symptoms compared to TG12 and TG13.


There is much variation in clinical status among 5T patients. All patients in this study with 5T/PS CF, all patients with both normal NPD and sweat test, and most patients with TG11 were stable or improving over time. Therefore, NPD measurement and TGm status aid to assess if a patient is at high risk for developing CF or CFTR-related disease and if specific follow up in a CF center is required.


CFTR function; CFTR-related disorder; Cystic fibrosis; IVS8-5T; Nasal potential difference; Sweat chloride


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