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Background: Non-invasive and sensitive clinical endpoints are needed to monitor onset and progression of early lung disease in children with cystic fibrosis (CF). We compared lung clearance index (LCI), FEV 1 , functional and structural lung magnetic resonance imaging (MRI) outcomes in Swiss children with CF diagnosed following newborn screening., Methods: Lung function (LCI, FEV 1 ) and unsedated functional and structural lung MRI was performed in 79 clinically stable children with CF (3 - 8 years) and 75 age-matched healthy controls. Clinical information was collected throughout childhood., Results: LCI, ventilation and perfusion defects, and structural MRI scores were significantly higher in children with CF compared with controls, but FEV 1 was not different between groups. Lung MRI outcomes correlated significantly with LCI (morphology score (r = 0.56, p < 0.001); ventilation defects (r = 0.43, p = 0.001); perfusion defects (r = 0.64, p < 0.001), but not with FEV 1 . Lung MRI outcomes were more sensitive to detect impairments in children with CF (abnormal ventilation and perfusion outcomes in 47 %, morphology score in 30 %) compared with lung function (abnormal LCI in 21 % and FEV 1 in 4.8 %). Pulmonary exacerbations, respiratory hospitalizations, and increase in patient-reported cough was associated with higher LCI and higher structural and functional MRI outcomes., Conclusions: The LCI and lung MRI outcomes non-invasively detect even mild early lung disease in young children with CF diagnosed following newborn screening. Pulmonary exacerbations and early respiratory symptoms were risk factors for structural and functional impairment in childhood., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Prof. P. Latzin reports the followind COIs: - Grants from Vertex and OM Pharma paid to the institution - Participation on data safety monitoring boards or advisory boards of Polyphor, Santhera DMC, Vertex, OM Pharma, Vifor, Sanofi Aventis - Payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events: Vertex, Vifor, OM Pharma Jakob Usemann reports: Grants from - Swiss lung foundation - Palatin Foundation, Basel, Switzerland Payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events: - Vertex - Zurich Lung foundation Support for attending meetings and/or travel from Vertex Kathryn Ramsey reports: Support for the present manuscript form: -Swiss National Science Foundation Ambizione Research Grant (168173), paid to the institution Leadership or fiduciary role in other board, society, committee or advocacy group, unpaid Global Lung Initiative MBW Task Force Elisabeth Kieninger reports: Payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events: Sanofi-Aventis., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: With improvement in supportive therapies and the introduction of cystic fibrosis transmembrane conductance regulator (CFTR)-modulator treatment in patients with cystic fibrosis (CF), milder disease courses are expected. Therefore, sensitive parameters are needed to monitor disease course and effects of CFTR-modulators. Functional lung MRI using matrix-pencil decomposition (MP-MRI) is a promising tool for assessing ventilation and perfusion quantitatively. This study aimed to assess the treatment effect of elexacaftor/tezacaftor/ivacaftor combination regimen (ELX/TEZ/IVA) on measures of structural and functional lung abnormalities., Methods: 24 children with CF underwent lung function tests (multiple breath washout, spirometry), functional and structural MRI twice (one year apart) before and once after at least two weeks (mean 4.7 ± 2.6 months) on ELX/TEZ/IVA. Main outcomes were changes (Δ) upon ELX/TEZ/IVA in lung function, defect percentage of ventilation (VDP) and perfusion (QDP), defect distribution index of ventilation and perfusion (DDI V, DDI Q ), and Eichinger score. Statistical analyses were performed using paired t-tests and multilevel regression models with bootstrapping., Results: We observed a significant improvement in lung function, structural and functional MRI parameters upon ELX/TEZ/IVA treatment (mean; 95%-CI): ΔLCI 2.5 (TO) -0.84 (-1.62 to -0.06); ΔFEV 1 (z-score) 1.05 (0.56 to 1.55); ΔVDP (% of impairment) -6.00 (-8.44 to -3.55); ΔQDP (% of impairment) -3.90 (-5.90 to -1.90); ΔDDI V -1.38 (-2.22 to -0.53); ΔDDI Q -0.31 (-0.73 to 0.12); ΔEichinger score -3.89 (-5.05 to -2.72)., Conclusions: Besides lung function tests, functional and structural MRI is a suitable tool to monitor treatment response of ELX/TEZ/IVA therapy, and seems promising as outcome marker in the future., (Copyright © 2022. Published by Elsevier B.V.)

Rationale: The lung clearance index (LCI) is increasingly being used in the clinical surveillance of patients with cystic fibrosis (CF). However, there are limited data on long-term variability and physiologically relevant changes in LCI during routine clinical surveillance., Objectives: To evaluate the long-term variability of LCI and propose a threshold for a physiologically relevant change., Methods: In children aged 4-18 years with CF, LCI was measured every 3 months as part of routine clinical surveillance during 2011-2020 in two centers. The variability of LCI during periods of clinical stability was assessed using mixed-effects models and was used to identify thresholds for physiologically relevant changes., Results: Repeated LCI measurements of acceptable quality (N = 858) were available in 100 patients with CF; for 74 patients, 399 visits at clinical stability were available. The variability of repeated LCI measurements over time expressed as the coefficient of variation (CV%) was 7.4%. The upper limit of normal (ULN) for relative changes in LCI between visits was 19%., Conclusion: We report the variability of LCI in children and adolescents with CF during routine clinical surveillance. According to our data, a change in LCI beyond 19% may be considered physiologically relevant. These findings will help guide clinical decisions according to LCI changes., (© 2022 Wiley Periodicals LLC.)

Background: The recently described sensor-crosstalk error in the multiple-breath washout (MBW) device Exhalyzer D (Eco Medics AG) could highly influence clinimetric properties and the current interpretation of MBW results. This study reanalyzes MBW data from clinical routine in the corrected software version Spiroware® 3.3.1 and evaluates the effect on outcomes., Methods: We included nitrogen-MBW data from healthy children and children with cystic fibrosis (CF) from previously published trials and ongoing cohort studies. We specifically compared lung clearance index (LCI) analyzed in Spiroware 3.2.1 and 3.3.1 with regard to (i) feasibility, (ii) repeatability, and (iii) validity as outcome parameters in children with CF., Results: (i) All previously collected measurements could be reanalyzed and resulted in unchanged feasibility in Spiroware 3.3.1. (ii) Short- and midterm repeatability of LCI was similar in both software versions. (iii) Clinical validity of LCI remained similar in Spiroware 3.3.1; however, this resulted in lower values. Discrimination between health and disease was comparable between both software versions. The increase in LCI over time was less pronounced with 0.16 LCI units/year (95% confidence interval [CI] 0.08; 0.24) versus 0.30 LCI units/year (95% CI 0.21; 0.38) in 3.2.1. Response to intervention in children receiving CF transmembrane conductance-modulator therapy resulted in a comparable improvement in LCI, in both Spiroware versions., Conclusion: Our study confirms that clinimetric properties of LCI remain unaffected after correction for the cross-sensitivity error in Spiroware software., (© 2022 The Authors. Pediatric Pulmonology published by Wiley Periodicals LLC.)

Nitrogen multiple-breath washout is an established technique to assess functional residual capacity and ventilation inhomogeneity in the lung. Accurate measurement of gas concentrations is essential for the appropriate calculation of clinical outcomes. We investigated the accuracy of oxygen and carbon dioxide gas sensor measurements used for the indirect calculation of nitrogen concentration in a commercial multiple-breath washout device (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and its impact on functional residual capacity and lung clearance index. High-precision calibration gas mixtures and mass spectrometry were used to evaluate sensor output. We assessed the impact of corrected signal processing on multiple-breath washout outcomes in a data set of healthy children and children with cystic fibrosis using custom analysis software. We found inadequate correction for the cross sensitivity of the oxygen and carbon dioxide sensors in the Exhalyzer D device. This results in an overestimation of expired nitrogen concentration and consequently, multiple-breath washout outcomes. Breath-by-breath correction of this error reduced the mean (SD) cumulative expired volume by 19.6% (5.0%), functional residual capacity by 8.9% (2.2%), and lung clearance index by 11.9% (4.0%). It also substantially reduced the level of the tissue nitrogen signal at the end of measurements. Inadequate correction for cross sensitivity in the oxygen and carbon dioxide gas sensors of the Exhalyzer D device leads to an overestimation of functional residual capacity and lung clearance index. Correction of this error is possible and could be applied by reanalyzing the measurements in an updated software version. NEW & NOTEWORTHY We investigated the sensor accuracy of a prominent nitrogen multiple-breath washout (N 2 MBW) device (Eco Medics AG, Duernten, Switzerland) as a possible cause of lack of comparability between outcomes of different MBW devices and methods. We identified an error in the nitrogen concentration calculation of this device, which results in a 10%-15% overestimation of primary outcomes, functional residual capacity, and lung clearance index. It also leads to a significant overestimation of nitrogen back-diffusion into the lungs.

Background: Although the lung clearance index (LCI) is a sensitive marker of small airway disease in individuals with cystic fibrosis (CF), less is known about longitudinal changes in LCI during routine clinical surveillance. Here, our objectives were to describe the longitudinal course of LCI in children with CF during routine clinical surveillance and assess influencing factors., Methods: Children with CF aged 3-18 years performed LCI measurements every 3 months as part of routine clinical care between 2011 and 2018. We recorded clinical data at every visit. We used a multilevel mixed effect model to determine changes in LCI over time and identify clinical factors that influence LCI course., Results: We collected LCI measurements from 1204 visits (3603 trials) in 78 participants, of which 907 visits had acceptable LCI data. The average unadjusted increase in LCI for the entire population was 0.29 (95% CI 0.20-0.38) LCI units·year -1 . The increase in LCI was more pronounced in adolescence (0.41 (95% CI 0.27-0.54) LCI units·year -1 ). Colonisation with either Pseudomonas aeruginosa or Aspergillus fumigatus , pulmonary exacerbations, CF-related diabetes and bronchopulmonary aspergillosis were associated with a higher increase in LCI over time. Adjusting for clinical risk factors reduced the increase in LCI over time to 0.24 (95% CI 0.16-0.33) LCI units·year -1 ., Conclusions: LCI measured during routine clinical surveillance is associated with underlying disease progression in children with CF. An increased change in LCI over time should prompt further diagnostic intervention., Competing Interests: Conflict of interest: B.S. Frauchiger has nothing to disclose. Conflict of interest: S. Binggeli has nothing to disclose. Conflict of interest: S. Yammine reports grants from Swiss National Science Foundation, outside the submitted work. Conflict of interest: B. Spycher reports grants from Swiss National Science Foundation and Swiss Cancer League, outside the submitted work. Conflict of interest: L. Krüger has nothing to disclose. Conflict of interest: K.A. Ramsey reports grants from Swiss National Science Foundation, outside the submitted work. Conflict of interest: P. Latzin reports grants from Vertex, during the conduct of the study; personal fees from Vertex, Novartis, Roche, Polyphor, Vifor, Gilead, Schwabe, Zambon and Santhera, grants from Vertex, outside the submitted work., (Copyright ©ERS 2021. For reproduction rights and permissions contact permissions@ersnet.org.)