Towards harmonization of solutions used for cystic fibrosis diagnosis by nasal potential difference measurements: A formulation approach with CHESS® software.

BACKGROUND: One diagnosis of cystic fibrosis involves measuring the nasal transepithelial potential difference (NPD) as a complementary technique in the forms of the disease, where the sweat test is non-discriminating. The NPD is measured using solutions with and without chlorides, containing a variety of substances whose activities on nasal mucus membranes are studied or assessed. Among the solutions described in the literature and used in specialized centers, none seems to be best adapted for industrial production for reasons of stability (formulas of the international consensus of Rowe et al. and formulas of Knowles et al.) and/or potential toxicity (formulas of Middleton et al.). OBJECTIVE(S): Defining new formulas, according to those of the international consensus, with greater physicochemical and microbiological stability. METHODS: The reformulation tests were conducted on the formulas of Rowe et al., using CHESS® (CHemical Equilibrium of Species and Surfaces) software for modeling aqueous systems that substantially reduced the number of experiments. CHESS® software was first validated using models of ideal and non-ideal solutions. Thereafter, experimentation was carried out for the sake of comparison with theoretical data. RESULTS: CHESS® software using models of ideal and non-ideal solutions were validated. The experimentation confirmed the theoretical data, and new formulas were assessed based on their physicochemical (pH, content, Osmolality) and microbiological stability. CONCLUSION: The new formulas defined here guarantee excellent physicochemical and microbiological stability of diagnostic solutions, indispensable criteria for harmonizing and comparing results from different specialized centers using NPD measurements. These new formulas apply to the harmonization approach of techniques for measuring the nasal transepithelial potential difference.

Correction to: In vitro prediction of stop-codon suppression by intravenous gentamicin in patients with cystic fibrosis: a pilot study.

The original article [1] contains errors in Table 1 affecting some of the presented oligonucleotide sequences and readthrough values in Table 1.

ECFS standards of care on CFTR-related disorders: Towards a comprehensive program for affected individuals.

After three publications defining an updated guidance on the diagnostic criteria for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (pwCFTR-RDs), establishing its relationship to CFTR-dysfunction and describing the individual disorders, this fourth and last paper in the series addresses some critical challenges facing health care providers and pwCFTR-RD. Topics included are: 1) benefits and obstacles to collect data from pwCFTR-RD are discussed, together with the opportunity to integrate them into established CF-registries; 2) the potential of infants designated CRMS/CFSPID to develop a CFTR-RD and how to communicate this information; 3) a description of the challenges in genetic counseling, with particular regard to phenotypic variability, unknown long-term evolution, CFTR testing and pregnancy termination 4) a proposal for the assessment of potential barriers to the implementation and dissemination of the produced documents to health care professionals involved in the care of pwCFTR-RD and a process to monitor the implementation of the CFTR-RD recommendations; 5) clinical trials investigating the efficacy of CFTR modulators in CFTR-RD and how endpoints and outcomes might be adapted to the heterogeneity of these disorders.

ECFS standards of care on CFTR-related disorders: Identification and care of the disorders.

This is the third paper in the series providing updated information and recommendations for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (CFTR-RD). This paper covers the individual disorders, including the established conditions - congenital absence of the vas deferens (CAVD), diffuse bronchiectasis and chronic or acute recurrent pancreatitis - and also other conditions which might be considered a CFTR-RD, including allergic bronchopulmonary aspergillosis, chronic rhinosinusitis, primary sclerosing cholangitis and aquagenic wrinkling. The CFTR functional and genetic evidence in support of the condition being a CFTR-RD are discussed and guidance for reaching the diagnosis, including alternative conditions to consider and management recommendations, is provided. Gaps in our knowledge, particularly of the emerging conditions, and future areas of research, including the role of CFTR modulators, are highlighted.

CFTR biomarkers: time for promotion to surrogate end-point.

In patients with cystic fibrosis, cystic fibrosis transmembrane conductance regulator (CFTR) biomarkers, such as sweat chloride concentration and/or nasal potential difference, are used as end-points of efficacy in phase-III clinical trials with the disease modifying drugs ivacaftor (VX-770), VX809 and ataluren. The aim of this project was to review the literature on reliability, validity and responsiveness of nasal potential difference, sweat chloride and intestinal current measurement in patients with cystic fibrosis. Data on clinimetric properties were collected for each biomarker and reviewed by an international team of experts. Data on reliability, validity and responsiveness were tabulated. In addition, narrative answers to four key questions were discussed and agreed by the team of experts. The data collected demonstrated the reliability, validity and responsiveness of nasal potential difference. Fewer data were found on reliability of sweat chloride concentration; however, validity and responsiveness were demonstrated. Validity was demonstrated for intestinal current measurement, but further information is required on reliability and responsiveness. For all three end-points, normal values were collected and further research requirements were proposed. This body of work adds useful information to support the promotion of CFTR biomarkers to surrogate end-points and to guide further research in the area.

ECFS standards of care on CFTR-related disorders: Updated diagnostic criteria.

This paper is the first in a series providing updated guidance on the definition, evaluation and management of people with a Cystic Fibrosis Transmembrane conductance Regulator (CFTR)-Related Disorder (CFTR-RD). The need for this update relates to more precise characterisation of CFTR gene variants and improved assessment of CFTR protein dysfunction. The exercise is co-ordinated by the European CF Society Standards of Care Committee and Diagnostic Network Working Group and involves stakeholder engagement. This first paper was produced by a core group using an extensive literature review and papers graded for their quality. Subsequent wider stakeholder agreement was achieved. The definition of a CFTR-RD remains "a clinical condition with evidence of CFTR protein dysfunction that does not fulfil the diagnostic criteria for CF". Clearer guidance on CFTR dysfunction and relevant CFTR variants will be provided. Thresholds for clinical presentations are presented and the paradigm that pathobiological processes may be evident in more than one organ is agreed. In this paper we reflect on the early patient journey, highlighting that CF specialists as well as other relevant specialists should be involved in the care of people with a CFTR-RD.

ECFS standards of care on CFTR-related disorders: Diagnostic criteria of CFTR dysfunction.

The spectrum of disorders involving CFTR (cystic fibrosis transmembrane conductance regulator) dysfunction correlates with a continuous gradient of CFTR function defined by the combination of two allelic CFTR variants. CFTR-related disorders are clinical entities with features of cystic fibrosis (CF) and evidence for presence of CFTR dysfunction but not meeting criteria for diagnosis of CF. Individuals with CFTR-RDs demonstrate a wide range of CFTR activity and are still under-recognized or misclassified. The level of CFTR dysfunction may be measured in vivo (sweat testing, nasal potential difference measurements) and/or by ex vivo tests (intestinal current measurement), or indirectly indicated by CFTR variants, as alteration in sequence of the CFTR gene translates into CFTR dysfunction. CFTR bioassays can aid in the diagnosis of individuals with CF, but we lack parameters to differentiate CF from CFTR-RD. In the era of the CFTR modulators and their potential clinical benefit, it is of utmost importance to diagnose CFTR-RD as unambiguously as possible. We therefore propose the following to define compatible CFTR dysfunction in a person with a suspected diagnosis of CFTR-RD : (1) evidence of CFTR dysfunction in vivo or ex vivo in at least two different CFTR functional test types, or (2) One CFTR variant known to reduce CFTR function and evidence of CFTR dysfunction in vivo or ex vivo in at least two different CFTR functional test types, or (3) Two CFTR variants shown to reduce CFTR function, with at most one CF-causing variant.

The very low penetrance of cystic fibrosis for the R117H mutation: a reappraisal for genetic counselling and newborn screening.

BACKGROUND: Cystic fibrosis (CF) is caused by compound heterozygosity or homozygosity of CF transmembrane conductance regulator gene (CFTR) mutations. Phenotypic variability associated with certain mutations makes genetic counselling difficult, notably for R117H, whose disease phenotype varies from asymptomatic to classical CF. The high frequency of R117H observed in CF newborn screening has also introduced diagnostic dilemmas. The aim of this study was to evaluate the disease penetrance for R117H in order to improve clinical practice. METHODS: The phenotypes in all individuals identified in France as compound heterozygous for R117H and F508del, the most frequent CF mutation, were described. The allelic prevalences of R117H (p(R117H)), on either intron 8 T5 or T7 background, and F508del (p(F508del)) were determined in the French population, to permit an evaluation of the penetrance of CF for the [R117H]+[F508del] genotype. RESULTS: Clinical details were documented for 184 [R117H]+[F508del] individuals, including 72 newborns. The disease phenotype was predominantly mild; one child had classical CF, and three adults' severe pulmonary symptoms. In 5245 healthy adults, p(F508del) was 1.06%, p(R117H;T7) 0.27% and p(R117H;T5)<0.01%. The theoretical number of [R117H;T7]+[F508del] individuals in the French population was estimated at 3650, whereas only 112 were known with CF related symptoms (3.1%). The penetrance of classical CF for [R117H;T7]+[F508del] was estimated at 0.03% and that of severe CF in adulthood at 0.06%. CONCLUSIONS: These results suggest that R117H should be withdrawn from CF mutation panels used for screening programmes. The real impact of so-called disease mutations should be assessed before including them in newborn or preconceptional carrier screening programmes.

Genetic diagnosis in practice: From cystic fibrosis to CFTR-related disorders.

Cystic fibrosis (CF) is a channelopathy caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein. Diagnosis of CF has long relied on a combination of clinical (including gastrointestinal and/or respiratory) symptoms and elevated sweat chloride concentration. After cloning of the CFTR gene in 1989, genetic analysis progressively became an important aspect of diagnosis. Although combination of sweat test and genetic analysis have simplified the diagnosis of CF in most cases, difficult situations remain, especially in cases that do not fulfill all diagnostic criteria. Such situations are most frequently encountered in patients presenting with a single-organ disease (e.g., congenital absence of the vas deferens, pancreatitis, bronchiectasis) leading to a diagnosis of CFTR-related disorder, or when the presence/ absence of CF is not resolved after newborn screening. This article reviews the diagnostic criteria of CF, with special emphasis on genetic testing. © 2020 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

A critical review of definitions used to describe Pseudomonas aeruginosa microbiological status in patients with cystic fibrosis for application in clinical trials.

BACKGROUND: Definition of Pseudomonas aeruginosa (Pa) microbiological status is essential for patients' inclusion in clinical trials. The aim of this study was to agree on the definitions of Pa infection status for initial infection, eradication and chronic infection to be used in clinical trials and to propose additional future study areas. METHODS: An exhaustive literature search was performed. The clinimetric properties of different definitions of Pa microbiological status were evaluated. RESULTS: Historical studies have mostly used culture-based definitions, although some have also involved complementary anti-Pa antibodies. Clinimetric analysis showed great variability in the definitions used, leading to differences in reliability, validity, responsiveness to treatment and correlation with outcome measures. Use of serology for initial Pa infection and successful Pa eradication introduced a greater level of complexity as antibody tests are not standardised. Moreover, the chronology of the immune response to Pa antigenic determinants was not completely clear. Chronic Pa infection was characterized by high levels of antibodies and good concordance between culture results and serology. CONCLUSIONS: Microbiological monitoring, regular sampling from the airways and standardization of culture methods remain essential requisites for microbiological definitions. Despite limitations, serology should be incorporated in the definitions of initial infection and eradication used in clinical trials to better classify patients at enrolment, mainly in non-expectorating children. This requires standardization of serological testing.

Guidelines for the management of children at risk of secondary bone fragility: Expert opinion of a French working group.

The current French national guidelines were elaborated by a working group consisting of experts in the field of pediatric endocrinology, rheumatology, hepatogastroenterology, nephrology, and pneumology. A systematic search was undertaken of the literature published between 2008 and 2018 and indexed in PubMed. The recommendations developed were then validated by an external evaluation group comprising representatives from the various highly specialized fields in pediatrics, representatives of the societies and groups supporting the development of the guidelines, and representatives of different healthcare professions. The objective of these guidelines was to detail the current optimal management of children at risk of secondary bone fragility.

Penetrance is a critical parameter for assessing the disease liability of CFTR variants.

BACKGROUND: Major issues of newborn screening (NBS) for CF are the assessment of disease liability of variants and of the penetrance of clinical CF, notably in inconclusive diagnosis. The penetrance of CF is defined as the risk of a particular genotype to lead to a CF phenotype. METHODS: We aimed to get insight into the penetrance of CF for fifteen CFTR variants: 5 frequent CF-causing and 10 classified as of varying clinical consequence (VCC) or associated with a CFTR-related disorder (CFTR-RD) in CFTR2 or CFTR-France databases. The penetrance was approached by: (1) comparison of variant allelic frequencies in CF patients (CFTR2) and in the general population; (2) estimation of the likelihood of a positive NBS test for the 14 compound heterozygous with F508del and the F508del homozygous genotypes, defined as the ratio of detected/expected number of neonates with a given genotype in the 2002-2017 period. RESULTS: A full penetrance was observed for severe CF-causing variants. Five variants were more frequently found in the general population than in CF patients: TG11T5, TG12T5, TG13T5, L997F and R117H;T7. The likelihood of a positive NBS test was 0.03% for TG11T5, 0.3% for TG12T5, 1.9% for TG13T5, 0.6% for L997F, 11.7% for D1152H, and 17.8% for R117H;T7. Penetrance varied greatly for variants with discrepant classification between CFTR2 and CFTR-France: 5.1% for R117C, 12.3% for T338I, 43.5% for D110H and 52.6% for L206W. CONCLUSION: These results illustrate the contribution of genetics population data to assess the disease liability of variants for diagnosis and genetic counselling purposes.

Efficacy and safety of ataluren in patients with nonsense-mutation cystic fibrosis not receiving chronic inhaled aminoglycosides: The international, randomized, double-blind, placebo-controlled Ataluren Confirmatory Trial in Cystic Fibrosis (ACT CF).

BACKGROUND: Ataluren was developed for potential treatment of nonsense-mutation cystic fibrosis (CF). A previous phase 3 ataluren study failed to meet its primary efficacy endpoint, but post-hoc analyses suggested that aminoglycosides may have interfered with ataluren's action. Thus, this subsequent trial (NCT02139306) was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation CF not receiving aminoglycosides. METHODS: Eligible subjects with nonsense-mutation CF (aged ≥6 years; percent predicted (pp) FEV1 ≥40 and ≤90) from 75 sites in 16 countries were randomly assigned in double-blinded fashion to receive oral ataluren or matching placebo thrice daily for 48 weeks. The primary endpoint was absolute change in average ppFEV1 from baseline to the average of Weeks 40 and 48. FINDINGS: 279 subjects were enrolled; 138 subjects in the ataluren arm and 136 in the placebo arm were evaluable for efficacy. Absolute ppFEV1 change from baseline did not differ significantly between the ataluren and placebo groups at Week 40 (-0.8 vs -1.8) or Week 48 (-1.7 vs -2.4). Average ppFEV1 treatment difference from baseline to Weeks 40 and 48 was 0.6 (95% CI -1.3, 2.5; p = 0.54). Pulmonary exacerbation rate per 48 weeks was not significantly different (ataluren 0.95 vs placebo 1.13; rate ratio p = 0.40). Safety was similar between groups. No life-threatening adverse events or deaths were reported. INTERPRETATION: Neither ppFEV1 change nor pulmonary exacerbation rate over 48 weeks were statistically different between ataluren and placebo groups. Development of a nonsense-mutation CF therapy remains elusive.

[Recommendations for the management of bone demineralization in cystic fibrosis]. / Recommandations pour la prise en charge de la déminéralisation osseuse dans la mucoviscidose.

A high prevalence of low bone mineralization is documented in adult patients with cystic fibrosis (CF). Osteopenia is present in as much as 85% of adult patients and osteoporosis in 13 to 57% of them. In children, studies are discordant probably because of different control database. Denutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity are well known risk factors for poor bone health. Puberty is a critical period and requires a careful follow-up for an optimal bone peak mass. This review is a consensus statement established by the national working group of the French Federation of CF Centers to develop practice guidelines for optimizing bone health in patients with CF. Recommendations for screening and for calcium, vitamin D and K supplementation are given. Further work is needed to define indications for treatment with biphosphonates and anabolic agents.

[Management of infants whose diagnosis is inconclusive at neonatal screening for cystic fibrosis]. / Recommandations pour la prise en charge et le suivi des nourrissons pour lesquels un diagnostic de mucoviscidose n'a pu être conclu après dépistage néonatal.

Neonatal screening for cystic fibrosis (CF) may detect infants with elevated immunoreactive trypsinogen (IRT) levels but with inconclusive sweat tests and/or DNA results. This includes cases associating (1) either the presence of at most one CF-causing mutation and sweat chloride values between 30 and 59mmol/L or (2) two CFTR mutations with at least one of unknown pathogenicity and a sweat chloride below 60mmol/L. This encompasses different clinical situations whose progression cannot be predicted. These cases require redoing the sweat test at 12 months and if possible at 6 and 24 months of life. This must be associated with extended genotyping. CFTR functional explorations can also help by investigating CFTR dysfunction. These infants must be initially evaluated in dedicated CF centers including bacteriological sputum analysis, chest radiology and fecal elastase dosage. A home practitioner must be informed of the specificity of follow-up. These infants will be reviewed in the CF center at 3, 6 and 12 months and every year. Any CF-related symptom requires reevaluation of the diagnosis. These guidelines were established by the "neonatal screening and difficult diagnoses" working group of the French CF Society. They aim to standardize management of infants with unclear diagnosis in French CF centers.

Guidelines for the clinical management and follow-up of infants with inconclusive cystic fibrosis diagnosis through newborn screening.

Neonatal screening for cystic fibrosis (CF) can detect infants with elevated immunoreactive trypsinogen (IRT) levels and inconclusive sweat tests and/or CFTR DNA results. These cases of uncertain diagnosis are defined by (1) either the presence of at most one CF-associated cystic fibrosis transmembrane conductance regulator (CFTR) mutation with sweat chloride values between 30 and 59mmol/L or (2) two CFTR mutations with at least one of unknown pathogenic potential and a sweat chloride concentration below 60mmol/L. This encompasses various clinical situations whose progression cannot be predicted. In these cases, a sweat chloride test has to be repeated at 12 months, and if possible at 6 and 24 months of life along with extended CFTR sequencing to detect rare mutations. When the diagnosis is not definite, CFTR functional explorations may provide a better understanding of CFTR dysfunction. The initial evaluation of these infants must be conducted in dedicated CF reference centers and should include bacteriological sputum analysis, chest radiology, and fecal elastase assay. The primary care physicians in charge of these patients should be familiar with the current management of CF and should work in collaboration with CF centers. A follow-up should be performed in a CF reference center at 3, 6, and 12 months of life and every year thereafter. Any symptom indicative of CF requires immediate reevaluation of the diagnosis. These guidelines were established by the "neonatal screening and difficult diagnoses" working group of the French CF society. Their objective is to standardize the management of infants with unclear diagnosis.

[Anti Pseudomonas aeruginosa antibiotic therapy in cystic fibrosis (exclusion of macrolides)]. / Stratégie antibiotique contre Pseudomonas aeruginosa dans la mucoviscidose (macrolides exclus).

Antibiotherapy is one of the main treatment in cystic fibrosis. Pseudomonas aeruginosa infection is one of the main causes of pulmonary degradation. The chronic sputum colonisation is characterized by the emergence of the mucoid phenotype, the formation of biofilm and the induction of excessive inflammatory response and consecutive tissue lesion. The choice of antibiotics depends on quantitative and qualitative analysis of sputum, bacteria resistance phenotypes and severity of infection. Treatment of P. aeruginosa is different in case of first colonization or chronic infection. In the first case, parenteral antibiotherapy (beta-lactams-aminoglycosids) followed by inhaled antibiotherapy may eradicate the germ. In the other case, superinfections can be treated with parenteral biantibiothérapy (beta-lactams or quinolons and aminoglycosides) during 15 to 21 days. This is associated with a better nutritional and respiratory status and a prolonged survival. Inhaled antibiotics between the courses have decreased the number of superinfections. This prolonged antibiotherapy must be monitored because of possible induction of bacterial resistance, nephrotoxicity and ototoxicity of aminosids and allergy to beta-lactams.