Improvement in Lung Clearance Index and Chest Computed Tomography Scores with Elexacaftor/Tezacaftor/Ivacaftor Treatment in People with Cystic Fibrosis Aged 12 Years and Older - The RECOVER Trial.

Rationale: Clinical trials have shown that use of elexacaftor/tezacaftor/ivacaftor (ETI) is associated with improvements in sweat chloride, pulmonary function, nutrition, and quality of life in people with cystic fibrosis (CF). Little is known about the impact of ETI on ventilation inhomogeneity and lung structure. Objectives: RECOVER is a real-world study designed to measure the impact of ETI in people with CF. The primary endpoints were lung clearance (lung clearance index; LCI2.5) and FEV1. Secondary endpoints included spirometry-controlled chest computed tomography (CT) scores. Methods: The study was conducted in seven sites in Ireland and the United Kingdom. Participants ages 12 years and older who were homozygous for the F508del mutation (F508del/F508del) or heterozygous for F508del and a minimum-function mutation (F508del/MF) were recruited before starting ETI and were followed up over 12 months. LCI2.5 was measured using nitrogen multiple breath washout (MBW) at baseline and at 6 and 12 months. Spirometry was performed as per the criteria of the American Thoracic Society and the European Respiratory Society. Spirometry-controlled chest CT scans were performed at baseline and at 12 months. CT scans were scored using the Perth Rotterdam Annotated Grid Morphometric Analysis (PRAGMA) system. Other outcome measures include weight, height, Cystic Fibrosis Quality of Life Questionnaire-Revised (CFQ-R), and sweat chloride. Measurements and Main Results: One hundred seventeen people with CF ages 12 and older were recruited to the study. Significant improvements were seen in LCI scores (-2.5; 95% confidence interval [CI], -3.0, -2.0) and in the percents predicted for FEV1 (8.9; 95% CI, 7.0, 10.9), FVC (6.6; 95% CI, 4.9, 8.3), and forced expiratory flow between 25% and 75% of expired volume (12.4; 95% CI, 7.8, 17.0). Overall PRAGMA-CF scores reflecting airway disease improved significantly (-3.46; 95% CI, -5.23, -1.69). Scores for trapped air, mucus plugging, and bronchial wall thickening improved significantly, but bronchiectasis scores did not. Sweat chloride levels decreased in both F508del/F508del (-43.1; 95% CI, -47.4, -38.9) and F508del/MF (-42.8; 95% CI, -48.5, -37.2) groups. Scores on the Respiratory Domain of the CFQ-R improved by 14.2 points (95% CI, 11.3, 17.2). At 1 year, sweat chloride levels were significantly lower for the F508del/F508del group compared with scores for the F508del/MF group (33.93 vs. 53.36, P < 0.001). Conclusions: ETI is associated with substantial improvements in LCI2.5, spirometry, and PRAGMA-CF CT scores in people with CF ages 12 years and older. ETI led to improved nutrition and quality of life. People in the F508del/F508del group had significantly lower sweat chloride on ETI treatment compared with the F508del/MF group. Clinical trial registered with www.clinicaltrials.gov (NCT04602468).

Clinical findings of patients with cystic fibrosis according to newborn screening results.

BACKGROUND: Cystic fibrosis (CF) is a lethal recessive genetic disease caused by loss of function associated with mutations in the CF trans-membrane conductance regulator. It is highly prevalent (approximately 1 in 3,500) in Caucasians. The aim of this study was to compare demographic and clinical features, diagnostic tests, treatments, and complications of patients with CF whose newborn screening (NBS) with twice-repeated immune reactive trypsinogen testing was positive, normal, and not performed. METHODS: In this study, 359 of all 1,488 CF patients recorded in the CF Registry of Turkey in 2018, who had been born through the process of NBS, were evaluated. Demographic and clinical features were compared in patients diagnosed with positive NBS (Group 1), normal (Group 2), or without NBS (Group 3). RESULTS: In Group 1, there were 299 patients, in Group 2, there were 40 patients, and in Group 3, there were 20 patients. Among all patients, the median age at diagnosis was 0.17 years. The median age at diagnosis was higher in Groups 2 and 3 than in Group 1 (P = 0.001). Fecal elastase results were higher in Group 2 (P = 0.033). The weight z-score was lower and chronic Staphylococcus aureus infection was more common in Group 3 (P = 0.017, P = 0.004, respectively). CONCLUSIONS: Frequency of growth retardation and chronic S. aureus infection can be reduced with an early diagnosis using NBS. In the presence of clinical suspicion in patients with normal NBS, further analyses such as genetic testing should be performed, especially to prevent missing patients with severe mutations.

Silver-manganese nanocomposite modified screen-printed carbon electrode in the fabrication of an electrochemical, disposable biosensor strip for cystic fibrosis.

A silver-manganese nanocomposite was successfully prepared by the urea hydrolysis method and used to detect chloride ions in sweat electrochemically. The synthesis involves the reaction of manganese sulphate, silver nitrate, and urea at 100 °C for 24 h. The crystalline nature of the particle was studied by diffraction analysis and found to be mixed-phase oxides of manganese alongside the oxides of silver. Morphological studies revealed the presence of quasi-prism-like structures, which is characteristic of ß-MnO2. A disposable sensor was fabricated by screen-printing the catalyst and used for the electrochemical detection of chloride ions in sweat. The sensor exhibited good selectivity, a sensitivity of 22.93 ± 0.64 µA mM-1 cm-2 in solution and 3010 ± 60 µA (log mM) -1 cm-2 for the fabricated sensor strip with a detection range from 5 mM up to 200 mM. The detection limit is 207 ± 7 µM (S/N = 3) in solution and 17 ± 6 µM for the fabricated sensor strip. The relative standard deviation (RSD) of sensor response is 2.38%. A prototype of the biosensor strip was fabricated and validated using real samples. This brings the possibility of developing a real-time biosensor strip for cystic fibrosis in point-of-care testing applications.

Audit of sweat chloride testing reveals analytical errors.

OBJECTIVES: Sweat chloride testing (SCT) is the mainstay for the diagnosis of cystic fibrosis (CF) and biomarker in the evaluation of CFTR-modifying drugs. To be a reliable and valid tool, analytical variance (CVA) must be minimized. However, external quality assessments have revealed significant deviations in routine clinical practice. Our goal was to identify and quantify technical errors through proficiency testing and simulations. METHODS: Chloride concentrations of three blinded samples (each as triplicates) were measured in 9 CF centers using a chloridometer in a routine setting. Technical errors were simulated and quantified in a series of measurements. We compared imprecision and bias before and after a counseling session by evaluating coefficients of variation (CV), adherence to tolerance limits, and inter-rater variability coefficients. RESULTS: Pipetting errors resulting in changes in sample volume were identified as the main source of error with deviations up to 41%. After the counseling session, the overall CVA decreased from 7.6 to 5.2%, the pass rate increased from 67 to 92%, and the inter-rater variability diminished. Significant deviations continued to be observed in individual centers. CONCLUSIONS: Prevention of technical errors in SCT decreases imprecision and bias. Quality assurance programs must be established in all CF centers, including staff training, standard operating procedures, and proficiency testing.

Correlating Cystic Fibrosis Transmembrane Conductance Regulator Function with Clinical Features to Inform Precision Treatment of Cystic Fibrosis.

Rationale: The advent of precision treatment for cystic fibrosis using small-molecule therapeutics has created a need to estimate potential clinical improvements attributable to increases in cystic fibrosis transmembrane conductance regulator (CFTR) function. Objectives: To derive CFTR function of a variety of CFTR genotypes and correlate with key clinical features (sweat chloride concentration, pancreatic exocrine status, and lung function) to develop benchmarks for assessing response to CFTR modulators. Methods: CFTR function assigned to 226 unique CFTR genotypes was correlated with the clinical data of 54,671 individuals enrolled in the Clinical and Functional Translation of CFTR (CFTR2) project. Cross-sectional FEV1% predicted measurements were plotted by age at which measurement was obtained. Shifts in sweat chloride concentration and lung function reported in CFTR modulator trials were compared with function-phenotype correlations to assess potential efficacy of therapies. Measurements and Main Results: CFTR genotype function exhibited a logarithmic relationship with each clinical feature. Modest increases in CFTR function related to differing genotypes were associated with clinically relevant improvements in cross-sectional FEV1% predicted over a range of ages (6-82 yr). Therapeutic responses to modulators corresponded closely to predictions from the CFTR2-derived relationship between CFTR genotype function and phenotype. Conclusions: Increasing CFTR function in individuals with severe disease will have a proportionally greater effect on outcomes than similar increases in CFTR function in individuals with mild disease and should reverse a substantial fraction of the disease process. This study provides reference standards for clinical outcomes that may be achieved by increasing CFTR function.

Clinical characteristics and genetic analysis of cystic fibrosis transmembrane conductance reseptor-related disease.

BACKGROUND: Cystic fibrosis (CF) transmembrane conductance receptor (CFTR)-related disease is diagnosed in patients affected by CFTR dysfunction who do not fully meet the CF diagnostic criteria. Only 2% of all CF patients have CFTR-related disease. We define the demographic characteristics of such patients, described the performance of mutational analyses, and describe the clinical findings. METHODS: Twenty-four patients were followed-up for CFTR-related disease. Patients with CF symptoms but who did not completely fulfil the CF diagnostic criteria were enrolled. Age, body mass index at the times of diagnosis and admission, symptoms, pulmonary function and fecal elastase test results, gene analyses, and clinical findings during follow-up were evaluated. RESULTS: Ten patients (42%) were female and 14 (58%) male. Their mean age was 15.3 years (minimum-maximum 6-20 years). The mean age at diagnosis was 8.5 years (minimum-maximum 3-14 years) and the most common presenting complaint was a cough (n = 19). During follow up, chronic sinusitis developed in 15 patients, bronchiectasis in 13, nasal polyposis in six, failure to thrive in three, recurrent pancreatitis in two, asthma in one, and congenital bilateral absence of the vas deferens in one. Fecal elastase levels were low in only one of the three patients who failed to thrive. In terms of CFTR gene mutations, two were found in 10 patients, one in eight patients, and none in six. CONCLUSIONS: Cystic fibrosis transmembrane conductance receptor-related disease presents with various clinical findings. Serious symptoms may develop later in life. Late diagnosis significantly compromises the quality and duration of life in such patients.

Treatment of Cystic Fibrosis Patients Homozygous for F508del with Lumacaftor-Ivacaftor (Orkambi®) Restores Defective CFTR Channel Function in Circulating Mononuclear Cells.

The treatment of cystic fibrosis (CF) patients homozygous for the F508del mutation with Orkambi®, a combination of a corrector (lumacaftor) and a potentiator (ivacaftor) of the mutated CFTR protein, resulted in some amelioration of the respiratory function. However, a great variability in the clinical response was also observed. The aim of this study was to evaluate the response to Orkambi® in a small cohort of F508del/F508del patients (n = 14) in terms of clinical and laboratory parameters, including ex vivo CFTR activity in mononuclear cells (MNCs), during a 12-month treatment. Patients responded with an increase in percent predicted forced expiratory volume in 1 s (FEV1%) and body mass index (BMI) as well as with a decrease in white blood cell (WBC) total counts and serum C-reactive protein (CRP) levels, although not significantly. Sweat chloride and CFTR-dependent chloride efflux were found to decrease and increase, respectively, as compared with pre-therapy values. CFTR and BMI showed a statistically significant correlation during Orkambi® treatment. Clustering analysis showed that CFTR, BMI, sweat chloride, FEV1%, and WBC were strongly associated. These data support the notion that CFTR-dependent chloride efflux in MNCs should be investigated as a sensitive outcome measure of Orkambi® treatment in CF patients.

Is it cystic fibrosis? The challenges of diagnosing cystic fibrosis.

The spectrum of conditions caused by abnormal CFTR function is broad - from 'classic' cystic fibrosis (CF) to single organ conditions termed CFTR-related disorders. Defining and securing the diagnosis in an important minority of patients can be a challenge as the sweat test is equivocal or normal; the impact this has on the patient (at different stages of their life) can be very significant as it has the potential to lead to misdiagnosis and over (or under) treatment with associated psychological burden. The nasal potential difference test and intestinal current measurements are physiological measurements of CFTR function and thus can provide important diagnostic information. This article provides an overview of the latest developments in CF diagnostics, outlining the approach to be taken when the diagnosis is unclear and some of the areas of uncertainty.

Tezacaftor/Ivacaftor in Subjects with Cystic Fibrosis and F508del/F508del-CFTR or F508del/G551D-CFTR.

RATIONALE: Tezacaftor (formerly VX-661) is an investigational small molecule that improves processing and trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) in vitro, and improves CFTR function alone and in combination with ivacaftor. OBJECTIVES: To evaluate the safety and efficacy of tezacaftor monotherapy and of tezacaftor/ivacaftor combination therapy in subjects with cystic fibrosis homozygous for F508del or compound heterozygous for F508del and G551D. METHODS: This was a randomized, placebo-controlled, double-blind, multicenter, phase 2 study (NCT01531673). Subjects homozygous for F508del received tezacaftor (10 to 150 mg) every day alone or in combination with ivacaftor (150 mg every 12 h) in a dose escalation phase, as well as in a dosage regimen testing phase. Subjects compound heterozygous for F508del and G551D, taking physician-prescribed ivacaftor, received tezacaftor (100 mg every day). MEASUREMENTS AND MAIN RESULTS: Primary endpoints were safety through Day 56 and change in sweat chloride from baseline through Day 28. Secondary endpoints included change in percent predicted FEV1 (ppFEV1) from baseline through Day 28 and pharmacokinetics. The incidence of adverse events was similar across treatment arms. Tezacaftor (100 mg every day)/ivacaftor (150 mg every 12 h) resulted in a 6.04 mmol/L decrease in sweat chloride and 3.75 percentage point increase in ppFEV1 in subjects homozygous for F508del, and a 7.02 mmol/L decrease in sweat chloride and 4.60 percentage point increase in ppFEV1 in subjects compound heterozygous for F508del and G551D from baseline through Day 28 (P < 0.05 for all). CONCLUSIONS: These results support continued clinical development of tezacaftor (100 mg every day) in combination with ivacaftor (150 mg every 12 h) in subjects with cystic fibrosis. Clinical trial registered with www.clinicaltrials.gov (NCT01531673).

Passively Addressable Ultra-Low Volume Sweat Chloride Sensor.

This work demonstrates a novel electrochemical biosensor for the detection of chloride ion levels in ultra-low volumes (1-3 microliters) of passively expressed human sweat. We present here a hydration monitor that the pediatric, geriatric, and other immune-compromised or physically inactive/sedentary population cohort can utilize, for whom the current methods of chloride quantification of active stimulation of sweat glands through iontophoresis or treadmill runs are unsuitable. In this work, non-faradaic electroanalysis using gold microelectrodes deposited on a flexible nanoporous substrate, for high nanoscale surface area to volume enhancement, was leveraged to operate in ultra-low sweat volumes of <3 µL eluted at natural rates. The specific chloride ionophore-based affinity of chloride ions resulted in the modulation of charge transfer within the electrical double layer at the electrode-sweat buffer interface, which was transduced using electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Linear calibration dose responses with R-squared values of 0.9746 and 0.9403 for EIS and CA respectively were obtained for a dynamic range of 10-100 mM. The surface charge and the binding chemistry of the capture probe were studied using zeta potential studies and UV-Vis. The dynamic sweat chloride-tracking capability of the sensor was evaluated for a duration of 180 min. Studies were conducted to probe the efficacy of the developed sensor for passive ultra-low sweat chloride assessment on human subjects (n = 3).

Super-Absorbent Polymer Valves and Colorimetric Chemistries for Time-Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin-Mounted Soft Microfluidics.

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.

Cystic Fibrosis Transmembrane Conductance Regulator-Related Metabolic Syndrome and Cystic Fibrosis Screen Positive, Inconclusive Diagnosis.

OBJECTIVE: An unintended consequence of cystic fibrosis (CF) newborn screening (NBS) is the identification of infants with a positive NBS test but inconclusive diagnostic testing. These infants are classified as CF transmembrane conductance regulator-related metabolic syndrome (CRMS) in the US and CF screen positive, inconclusive diagnosis (CFSPID) in other countries. Diagnostic and management decisions of these infants are challenges for CF healthcare professionals and stressful situations for families. As CF NBS has become more widespread across the world, increased information about the epidemiology and outcomes of these infants is becoming available. These data were reviewed at the 2015 CF Foundation Diagnosis Consensus Conference, and a harmonized definition of CRMS and CFSPID was developed. STUDY DESIGN: At the consensus conference, participants reviewed published and unpublished studies of CRMS/CFSPID and used a modified Delphi methodology to develop a harmonized approach to the definition of CRMS/CFSPID. RESULTS: Several studies of CRMS/CFSPID from populations around the world have been published in the past year. Although the studies vary in the number of infants studied, study design, and outcome measures, there have been some consistent findings. CRMS/CFSPID occurs relatively frequently, with CF:CRMS that ranges from 3 to 5 cases of CF for every 1 case of CRMS/CFSPID in regions where gene sequencing is not used. The incidence varies by NBS protocol used, and in some regions more cases of CRMS/CFSPID are detected than cases of CF. The majority of individuals with CRMS/CFSPID do not develop CF disease or progress to a diagnosis of CF. However, between 10% and 20% of asymptomatic infants can develop clinical features concerning for CF, such as a respiratory culture positive for Pseudomonas aeruginosa. Most studies have only reported short-term outcomes in the first 1-3 years of life; the long-term outcomes of CRMS/CFSPID remain unknown. The European CF Society definition of CFSPID and the CF Foundation definition of CRMS differ only slightly, and the consensus conference was able to create a unified definition of CRMS/CFSPID. CONCLUSIONS: CRMS/CFSPID is a relatively common outcome of CF NBS, and clinicians need to be prepared to counsel families whose NBS test falls into this classification. The vast majority of infants with CRMS/CFSPID will remain free from disease manifestations early in life. However, a small proportion may develop clinical features concerning for CF or demonstrate progression to a clinical phenotype compatible with a CF diagnosis, and their long-term outcomes are not known. A consistent international definition of CRMS/CFSPID will allow for better data collection for study of outcomes and result in improved patient care.

Clinical and laboratory profile of children with Cystic Fibrosis: Experience of a tertiary care center in Pakistan.

OBJECTIVE: To determine the clinical presentation, diagnostic investigations and laboratory workup done in admitted children with cystic fibrosis at Aga Khan University Hospital Karachi, Pakistan. METHODS: This is athree years retrospective study from January 2013 to December 2015 conducted at The Aga Khan University Hospital Karachi Pakistan, enrolling admitted patient from birth to 15 years of either gender, diagnosed with CF on the basis of clinical features and positive sweat chloride test. Different clinical presentations were noted including initial presentations. Sweat chloride values more than 60mmol/L were labeled as positive and consistent with diagnosis of CF. Available Delta F-508 mutation analyses were noted. Relevant laboratory and radiological investigations including sputum culture and HR-CT chest findings were documented. Results were analyzed using SPSS version 20. RESULTS: Total 43 children were selected according to the inclusion criteria. Chronic cough (69.76%) was the most common initial clinical presentation. Mean age at onset of symptoms was 14.41± 26.18 months and mean age at diagnosis was 47.20 ± 45.80 months Respiratory features were most common in our cohort including chronic productive cough (90.71%), recurrent bronchopneumonia (72.09%) and asthma like presentation (44.19%) with wheezing and cough. 86% patients presented with failure to thrive. Gastroenterological features including steatorrhea were seen in 55.81% patients and 44.19% patients had abdominal distension. Mean sweat chloride value in our population was 82.70± 22.74. Gene analysis for Delta F-508 was identified in 12 (27.90%) patients. Bronchiectatic pulmonary changes on HRCT were seen in 18 patients (41.86%). Pseudomonas grew in 12 patients (27.90%) in sputum cultures at the time of diagnosis. CONCLUSION: Respiratory presentations predominate in CF children followed by gastrointestinal features. Nearly half of our patient had bronchiectatic changes on CT scan chest and more than quarter had pseudomonas colonization in the airways at the time of diagnosis. Delta F-508 mutation was found to be uncommon in our study population. There is significant delay in diagnosing patients with CF.

Heterogeneity of CFTR modulator-induced sweat chloride concentrations in people with cystic fibrosis.

BACKGROUND: Sweat chloride (SC) concentrations in people with cystic fibrosis (PwCF) reflect relative CF transmembrane conductance regulator (CFTR) protein function, the primary CF defect. Populations with greater SC concentrations tend to have lesser CFTR function and more severe disease courses. CFTR modulator treatment can improve CFTR function within specific CF genotypes and is commonly associated with reduced SC concentration. However, SC concentrations do not necessarily fall to concentrations seen in the unaffected population, suggesting potential for better CFTR treatment outcomes. We characterized post-modulator SC concentration variability among CHEC-SC study participants by genotype and modulator. METHODS: PwCF receiving commercially approved modulators for ≥90 days were enrolled for a single SC measurement. Clinical data were obtained from chart review and the CF Foundation Patient Registry (CFFPR). Variability of post-modulator SC concentrations was assessed by cumulative SC concentration frequencies. RESULTS: Post-modulator SC concentrations (n = 3787) were collected from 3131 PwCF; most (n = 1769, 47 %) were collected after elexacaftor/tezacaftor/ivacaftor (ETI) treatment. Modulator use was associated with lower SC distributions, with post-ETI concentrations the lowest on average. Most post-ETI SC concentrations were <60 mmol/L (79 %); 26 % were <30 mmol/L. Post-ETI distributions varied by genotype. All genotypes containing at least one F508del allele had individuals with post-ETI SC ≥60 mmol/L, with the largest proportion being F508del/minimal function (31 %). CONCLUSIONS: Post-modulator SC concentration heterogeneity was observed among all genotypes and modulators, including ETI. The presence of PwCF with post-modulator SC concentrations within the CF diagnostic range suggests room for additional treatment-associated CFTR restoration in this population.

Skin-Interfaced Bifluidic Paper-Based Device for Quantitative Sweat Analysis.

The erratic, intermittent, and unpredictable nature of sweat production, resulting from physiological or psychological fluctuations, poses intricacies to consistently and accurately sample and evaluate sweat biomarkers. Skin-interfaced microfluidic devices that rely on colorimetric mechanisms for semi-quantitative detection are particularly susceptible to these inaccuracies due to variations in sweat secretion rate or instantaneous volume. This work introduces a skin-interfaced colorimetric bifluidic sweat device with two synchronous channels to quantify sweat rate and biomarkers in real-time, even during uncertain sweat activities. In the proposed bifluidic-distance metric approach, with one channel to measure sweat rate and quantify collected sweat volume, the other channel can provide an accurate analysis of the biomarkers based on the collected sweat volume. The closed channel design also reduces evaporation and resists contamination from the external environment. The feasibility of the device is highlighted in a proof-of-the-concept demonstration to analyze sweat chloride for evaluating hydration status and sweat glucose for assessing glucose levels. The low-cost yet highly accurate device provides opportunities for clinical sweat analysis and disease screening in remote and low-resource settings. The developed device platform can be facilely adapted for the other biomarkers when corresponding colorimetric reagents are exploited.

Characterizing CFTR modulated sweat chloride response across the cf population: Initial results from the CHEC-SC study.

BACKGROUND: CHEC-SC is an ongoing epidemiologic study characterizing modulator-induced sweat chloride (SC) responses across the CF population, with interim results available prior to the availability of triple combination modulator therapy. METHODS: Eligible participants had been prescribed a modulator for ≥90 days with re-enrollment allowed upon establishment of a new modulator. Pre-modulator SC values were obtained from chart review; post-modulator sweat was collected and analyzed locally. SC changes were descriptively summarized with biologic sex effects adjusted for age, weight, and CFTR genotype. Heterogeneity in ivacaftor SC response was characterized in relation to published CFTR functional responses. RESULTS: 1848 participants provided 2004 SC measurements, 26.2% on ivacaftor, 39.1% on lumacaftor/ivacaftor, and 34.7% on tezacaftor/ivacaftor. Average SC changes for all modulators were consistent with those reported in previous clinical studies, with greater variation in SC response observed among rarer mutations and notable shifts in the proportion with SC <60mmol/L independent of the magnitude of SC change. Ivacaftor induced in vitro CFTR functional change was significantly correlated with ivacaftor-modulated SC response (Pearson correlation= ‒0.52, 95% CI: ‒0.773, ‒0.129). Average SC change from ivacaftor to tezacaftor/ivacaftor was ‒4.9 mmol/L (n=17,95% CI:‒9.3, ‒0.5) and differed from those switching from lumacaftor/ivacaftor (10.0 mmol/L, n=139, 95% CI:7.8,12.3). Sex at birth was not associated with SC response. CONCLUSIONS: CHEC-SC is the largest study characterizing modulator-induced SC changes across the CF population. There was a strong association between ivacaftor induced in vitro CFTR function and SC response across a genotypically heterogenous cohort. Biological sex was not associated with SC response.

Lung clearance index in children with cystic fibrosis previously diagnosed with CRMS/CFSPID: A monocentric prospective experience.

INTRODUCTION: No data are available on the values and role of lung clearance index (LCI) in cystic fibrosis (CF) Screen Positive Inconclusive Diagnosis (CFSPID) progressed to CF diagnosis (CFSPID > CF). This study aimed to assess the value of the LCI in correctly predicting the progression of CFSPID to CF. METHODS: This is a prospective study carried out at the CF Regional Center of Florence, Italy from September 1, 2019. We compared LCI values in children with CF diagnosed for positive newborn screening (NBS), CFSPID or CFSPID > CF for pathological sweat chloride (SC). The Exhalyzer-D (EcoMedics AG, Duernten, Switzerland, software version 3.3.1) was used to conduct the LCI tests, every 6 months on stable children. RESULTS: Forty-two cooperating children were enrolled (mean age at LCI tests: 5.4 years, range: 2.7-8.7): 26 (62%) had CF, 8 (19%) were CFSPID > CF for positive SC, while 8 (19%) kept the CFSPID label at last LCI test. The mean LCI value for patients with CF (7.39; 5.98-10.24) was statistically higher compared to both the mean LCI in the CFSPID > CF (6.62; 5.69-7.58) and in CFSPID (6.56; 5.64-7.21). CONCLUSIONS: Most of asymptomatic CFSPID or progressed to CF have normal LCI. Further data on the longitudinal course of LCI during follow up of CFSPID and on larger cohorts is needed.