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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Primary sclerosing cholangitis is associated with abnormalities in CFTR

BACKGROUND

The etiology of primary sclerosing cholangitis (PSC) is unknown. PSC and Cystic Fibrosis related liver disease have common features: chronic inflammation, biliary damage and similar cholangiographic findings. It is unknown whether or not PSC is related to cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. We hypothesize that a sub-group of PSC patients may be a "single-organ" presentation of CF.

METHODS

Patients with PSC underwent nasal potential difference (NPD) measurement, sweat chloride measurement and complete CFTR sequencing by new generation sequencing.

RESULTS

6/32 patients aged 46 ± 13 yrs. had CFTR causing mutations on one allele and 19 had CFTR polymorphisms; 6/23 tested had abnormal and 21 had intermediate sweat tests; 4/32 patients had abnormal NPD. One patient had chronic pancreatitis and was infertile.

CONCLUSIONS

19% of PSC patients had features of CFTR related disorder, 19% carry CFTR mutations and 50% had CFTR polymorphisms. In some patients, PSC may be a single organ presentation of CF or a CFTR-related disorder.

Evaluation of the intestinal current measurement method as a diagnostic test for cystic fibrosis

BACKGROUND

The sweat test and nasal potential difference measurement are now established tools in the diagnostic work up of cystic fibrosis (CF). Intestinal current measurement (ICM) is under consideration as an aid in the diagnosis of CF especially in young children. The aim of this study is to evaluate the diagnostic reliability of ICM.

METHODS

Rectal biopsies were obtained from three groups: CF patients, controls, and patients who were suspected for CF. ICMs were performed by mounting the rectal biopsy in an Ussing chamber and sequentially adding secretagogues while recording current changes.

RESULTS

Twenty-one CF patients (aged 3.0 ± 3.8 years) and 16 controls (aged 15.6 ± 15.1 years) were examined and have remarkably different results (presented as µA/cm(2) ): carbachol 16.3 ± 6.9, histamine 13.2 ± 8.9, and cAMP/forskolin 4.8 ± 4.0 for control group and carbachol -1.5 ± 5.3 (P < 0.0001), histamine -1.5 ± 3.1 (P < 0.0001), and cAMP/forskolin 0.36 ± 0.67 (P < 0.0001) for the CF group. Our suggested reference values are: +5.40, +3.52, +2.19 for carbachol, histamine, and cAMP/forskolin, respectively. The combination parameter (the arithmetic sum of carbachol, histamine, and cAMP/forskolin) of +7.19 differentiates normal from abnormal (ROC curve analysis, area under the curve = 1.00, both sensitivity and specificity are 100%). This statistical model was applied to 71 patients suspected for CF and revealed that 66 patients had normal ICM results (combination >7.19) and five patients had abnormal ICM results (combination <7.19).

CONCLUSION

We have shown that ICM tests may be useful to differentiate between patients suspected to have CF. These results require confirmation so that ICM may be included in diagnostic algorithms.

Urban daily life routines and human exposure to environmental discomfort

This study suggests a shift in focus from studying environmental discomfort in urban strategic stations, from which average results for the city or specific results for selected sites are deduced, and from measuring environmental conditions in fixed monitoring stations to a study in which we monitor, with mobile portable sensors, the exposure of people to environmental sources of discomfort while performing their daily life activities. Significant variations in sense of discomfort were measured in this study, and almost half of this variability was found to be explained while four independent environmental variables were considered: air quality (concentrations of CO), noise level, climatic variables (thermal load), and social loads. The study conducted in the city of Tel Aviv, which suffers from hot, humid summers and cool winters, and noise levels that reach the average levels of 85 dB, and relatively lower levels of exposure to the other potential stressors. These levels of combined exposures result in moderate levels of discomfort for young, healthy people once they experience the more stressing environments in the city. It is shown also that noise from other people is the most salient source of discomfort in Tel Aviv. Levels of discomfort accumulate during the working hours, either due to the impact of social loads or noise, but the subjects showed good coping abilities that enabled them to recover in late afternoons. It seems that thermal load does not have immediate impact, but rather cumulative ones, mainly during transitional seasons when subjects are less adaptive to extreme changes in weather.

Chronic ataluren (PTC124) treatment of nonsense mutation cystic fibrosis

In a subset of patients with cystic fibrosis (CF), nonsense mutations (premature stop codons) disrupt production of full-length, functional CF transmembrane conductance regulator (CFTR). Ataluren (PTC124) allows ribosomal readthrough of premature stop codons in mRNA. We evaluated drug activity and safety in patients with nonsense mutation CF who took ataluren three times daily (morning, midday and evening) for 12 weeks at either a lower dose (4, 4 and 8 mg·kg(-1)) or higher dose (10, 10 and 20 mg·kg(-1)). The study enrolled 19 patients (10 males and nine females aged 19-57 yrs; dose: lower 12, higher seven) with a classic CF phenotype, at least one CFTR nonsense mutation allele, and an abnormal nasal total chloride transport. Both ataluren doses were similarly active, improving total chloride transport with a combined mean change of -5.4 mV (p<0.001), and on-treatment responses (at least -5 mV improvement) and hyperpolarisations (values more electrically negative than -5 mV) in 61% (p<0.001) and 56% (p = 0.002) of patients. CFTR function was greater with time and was accompanied by trends toward improvements in pulmonary function and CF-related coughing. Adverse clinical and laboratory findings were uncommon and usually mild. Chronic ataluren administration produced time-dependent improvements in CFTR activity and clinical parameters with generally good tolerability.

Effectiveness of PTC124 treatment of cystic fibrosis caused by nonsense mutations: a prospective phase II trial

BACKGROUND

In about 10% of patients worldwide and more than 50% of patients in Israel, cystic fibrosis results from nonsense mutations (premature stop codons) in the messenger RNA (mRNA) for the cystic fibrosis transmembrane conductance regulator (CFTR). PTC124 is an orally bioavailable small molecule that is designed to induce ribosomes to selectively read through premature stop codons during mRNA translation, to produce functional CFTR.

METHODS

This phase II prospective trial recruited adults with cystic fibrosis who had at least one nonsense mutation in the CFTR gene. Patients were assessed in two 28-day cycles. During the first cycle, patients received PTC124 at 16 mg/kg per day in three doses every day for 14 days, followed by 14 days without treatment; in the second cycle, patients received 40 mg/kg of PTC124 in three doses every day for 14 days, followed by 14 days without treatment. The primary outcome had three components: change in CFTR-mediated total chloride transport; proportion of patients who responded to treatment; and normalisation of chloride transport, as assessed by transepithelial nasal potential difference (PD) at baseline, at the end of each 14-day treatment course, and after 14 days without treatment. The trial was registered with who.int/ictrp, and with clinicaltrials.gov, number NCT00237380.

FINDINGS

Transepithelial nasal PD was evaluated in 23 patients in the first cycle and in 21 patients in the second cycle. Mean total chloride transport increased in the first treatment phase, with a change of -7.1 (SD 7.0) mV (p<0.0001), and in the second, with a change of -3.7 (SD 7.3) mV (p=0.032). We recorded a response in total chloride transport (defined as a change in nasal PD of -5 mV or more) in 16 of the 23 patients in the first cycle's treatment phase (p<0.0001) and in eight of the 21 patients in the second cycle (p<0.0001). Total chloride transport entered the normal range for 13 of 23 patients in the first cycle's treatment phase (p=0.0003) and for nine of 21 in the second cycle (p=0.02). Two patients given PTC124 had constipation without intestinal obstruction, and four had mild dysuria. No drug-related serious adverse events were recorded.

INTERPRETATION

In patients with cystic fibrosis who have a premature stop codon in the CFTR gene, oral administration of PTC124 to suppress nonsense mutations reduces the epithelial electrophysiological abnormalities caused by CFTR dysfunction.

Nasal potential difference in non-classic cystic fibrosis-long term follow up

BACKGROUND

Nasal potential difference (NPD) measurement is an electrophysiological test that assesses cystic fibrosis transmembrane conductance regulator (CFTR) activity and is a recognized diagnostic tool in CF. The aim of this study is to assess in the long term the role of NPD in patients whose diagnosis is questionable.

METHODS

We performed follow up study on 70 patients with questionable CF (QCF) who were divided previously into two groups according to their NPD results: patients who likely have CF (QCF-CF) (n = 24), and those who likely do not have CF (QCF-non-CF) (n = 46).

RESULTS

Sixty out of 70 patients were available for study. Sixteen patients in the QCF-CF group were being followed up at CF Centers as opposed to 1 in the QCF-non-CF group (P < 0.01). Seven patients from the QCF-CF group developed sinusitis during the follow up years compared to none from the QCF-non-CF group. During the years of the follow up, 17 QCF-non-CF patients were diagnosed with other medical conditions that could explain their previous symptoms. On repeated NPD measurement in the QCF-CF group, the results were similar to the original test.

CONCLUSIONS

This study supports the diagnostic role of NPD measurement. Larger cohort studies are required for confirmation.

Reproducibility of nasal potential difference measurements in cystic fibrosis

BACKGROUND

Nasal potential difference (NPD) measurement has been advocated as a diagnostic tool for cystic fibrosis (CF) patients and as a method for assessing the response to new therapies. The purpose of this study was to examine the reproducibility of NPD measurements performed in a single center.

METHODS

A total of 68 CF patients with a mean (+/- SD) age of 16 +/- 8 years (age range, 6 to 52 years) underwent NPD measurements on at least two occasions.

RESULTS

A total of 25 patients with classic CF (mean age, 21 +/- 8 years) and 43 patients with nonclassic CF (mean age, 14 +/- 8 years) underwent sweat tests and NPD measurements. The mean sweat chloride values were 102 +/- 18 and 54 +/- 14 mEq/L, respectively, for classic CF and nonclassic CF groups. All patients underwent repeat NPD measurements. The basal NPD and the response to amiloride (DeltaAmil) and response to Cl(-) free and isoproterenol (DeltaCl(-) free + iso) were very similar in both measurements. In the classic CF group, the basal potential difference values were -40 +/- 12 vs -39 +/- 11 mV (p = 0.57), respectively, for the first and second measurements; 27 +/- 9 vs 26 +/- 10 mV (p = 0.55), respectively, for DeltaAmil; and 2.1 +/- 3.8 vs 0.4 +/- 2.9 mV (p = 0.07), respectively, for DeltaCl(-) free + iso. In the nonclassic CF group, the values were -32 +/- 13 vs -28 +/- 10 mV (p = 0.008), respectively; 19 +/- 10 vs 17 +/- 8 mV (p = 0.388), respectively; and -3.2 +/- 4.6 vs -3.3 +/- 4.4 mV (p = 0.876), respectively.

CONCLUSION

When performed in a single center, NPD is a reproducible test for CF patients and thus may be a useful outcome measurement for assessment of the efficacy of new treatments.