Prime editing functionally corrects cystic fibrosis-causing CFTR mutations in human organoids and airway epithelial cells.

Prime editing is a recent, CRISPR-derived genome editing technology capable of introducing precise nucleotide substitutions, insertions, and deletions. Here, we present prime editing approaches to correct L227R- and N1303K-CFTR, two mutations that cause cystic fibrosis and are not eligible for current market-approved modulator therapies. We show that, upon DNA correction of the CFTR gene, the complex glycosylation, localization, and, most importantly, function of the CFTR protein are restored in HEK293T and 16HBE cell lines. These findings were subsequently validated in patient-derived rectal organoids and human nasal epithelial cells. Through analysis of predicted and experimentally identified candidate off-target sites in primary stem cells, we confirm previous reports on the high prime editor (PE) specificity and its potential for a curative CF gene editing therapy. To facilitate future screening of genetic strategies in a translational CF model, a machine learning algorithm was developed for dynamic quantification of CFTR function in organoids (DETECTOR: "detection of targeted editing of CFTR in organoids").

Genetic Spectrum and Clinical Characteristics of Patients with Primary Ciliary Dyskinesia: a Belgian Single Center Study.

PURPOSE: We aimed to examine the correlation between clinical characteristics and the pathogenic gene variants in patients with Primary Ciliary Dyskinesia (PCD). METHODS: We conducted a retrospective single-center study in patients with PCD followed at the University Hospitals Leuven. We included patients with genetically confirmed PCD and described their genotype, data from ultrastructural ciliary evaluation and clinical characteristics. Genotype/phenotype correlations were studied in patients with the most frequently involved genes. RESULTS: We enrolled 74 patients with a median age of 25.58 years. The most frequently involved genes were DNAH11 (n = 23) and DNAH5 (n = 19). The most frequent types of pathogenic variants were missense (n = 42) and frameshift variants (n = 36) and most patients had compound heterozygous variants (n = 44). Ciliary ultrastructure (p < 0.001), situs (p = 0.015) and age at diagnosis (median 9.50 vs 4.71 years, p = 0.037) differed between DNAH11 and DNAH5. When correcting for situs this difference in age at diagnosis was no longer significant (p = 0.973). Patients with situs inversus were diagnosed earlier (p = 0.031). Respiratory tract microbiology (p = 0.161), lung function (cross-sectional, p = 0.829 and longitudinal, p = 0.329) and chest CT abnormalities (p = 0.202) were not significantly different between DNAH11 and DNAH5 variants. CONCLUSION: This study suggests a genotype-phenotype correlation for some of the evaluated clinical characteristics of the two most frequently involved genes in this study, namely DNAH11 and DNAH5.

Respiratory morbidity in patients with spinal muscular atrophy-a changing world in the light of disease-modifying therapies.

Respiratory complications are common in spinal muscular atrophy (SMA) and significantly contribute to morbidity and mortality in these patients. Generalized respiratory and bulbar muscle weakness translates into diverse and complex clinical consequences necessitating strict follow-up and specialized care. The natural history of SMA has evolved drastically in recent years as a result of the introduction of novel, disease-modifying therapies. While the impact of these therapies on motor function is well described in literature, its consequence for respiratory management has not been extensively studied. In this review we aim to provide a comprehensive overview of the respiratory morbidities, their follow-up, management, and the impact of novel therapies in SMA.

Reversible Hypothalamic Obesity in a Girl with Suprasellar Tuberculoma.

INTRODUCTION: Suprasellar tuberculoma are extremely rare in children and most of those patients present with headache, vomiting, visual disturbances, and hypofunction of the pituitary gland. In this case report, we present a girl with tuberculosis, who developed significant weight gain in combination with pituitary dysfunction, which recovered after antituberculosis treatment. CASE PRESENTATION: An 11-year old girl presented with headache, fever and anorexia that progressively evolved into an encephalopathic status with cranial nerves III and VI paresis. Brain MRI showed meningeal contrast capture along cranial nerves II (including optic chiasm), III, V and VI bilaterally and multiple contrast enhancing brain parenchyma lesions. Tuberculin skin test was negative but interferon-gamma release assay was positive. The clinical and radiological working diagnosis was consistent with tuberculous meningoencephalitis. Pulse corticosteroids for 3 days and quadruple antituberculosis therapy were started and the girl demonstrated obvious improvement of her neurological symptoms. However, after a few months of therapy she developed remarkable weight gain (+20 kg in 1 year) and growth arrest. Her hormone profile revealed insulin resistance (homeostasis model assessment-estimated insulin resistance [HOMA-IR] 6.8) despite putative growth hormone deficiency (circulating insulin-like growth factor-I [IGF-I] 104 µg/L [-2.4 SD]). Follow-up brain MRI showed a decrease in basal meningitis, but increased parenchymal lesions in the suprasellar region extending medially into the nucleus lentiformis, with now a voluminous tuberculoma at this site. Antituberculosis treatment was continued for a total of 18 months. The patient improved clinically, she regained her pre-illness Body Mass Index (BMI) SDS and her growth rate increased slightly. On the hormonal side, disappearance of insulin resistance (HOMA-IR 2.5) and an increase in IGF-I (175 µg/L, -1.4 SD) was noted, and her last brain MRI showed a remarkable volume reduction of the suprasellar tuberculoma. CONCLUSION: Suprasellar tuberculoma can have a very dynamic presentation during the active stage of the disease, which can be reversed by prolonged antituberculosis treatment. Previous studies showed that the tuberculous process can also cause long term and irreversible changes in the hypothalamic-pituitary axis. Prospective studies are however needed in the pediatric population to know the exact incidence and type of pituitary dysfunction.

Nanoblades allow high-level genome editing in murine and human organoids.

Genome engineering has become more accessible thanks to the CRISPR-Cas9 gene-editing system. However, using this technology in synthetic organs called "organoids" is still very inefficient. This is due to the delivery methods for the CRISPR-Cas9 machinery, which include electroporation of CRISPR-Cas9 DNA, mRNA, or ribonucleoproteins containing the Cas9-gRNA complex. However, these procedures are quite toxic for the organoids. Here, we describe the use of the "nanoblade (NB)" technology, which outperformed by far gene-editing levels achieved to date for murine- and human tissue-derived organoids. We reached up to 75% of reporter gene knockout in organoids after treatment with NBs. Indeed, high-level NB-mediated knockout for the androgen receptor encoding gene and the cystic fibrosis transmembrane conductance regulator gene was achieved with single gRNA or dual gRNA containing NBs in murine prostate and colon organoids. Likewise, NBs achieved 20%-50% gene editing in human organoids. Most importantly, in contrast to other gene-editing methods, this was obtained without toxicity for the organoids. Only 4 weeks are required to obtain stable gene knockout in organoids and NBs simplify and allow rapid genome editing in organoids with little to no side effects including unwanted insertion/deletions in off-target sites thanks to transient Cas9/RNP expression.

Understanding and managing respiratory infections in children and young adults with neurological impairment.

INTRODUCTION: Patients with neurocognitive impairment (NI) have multiple medical needs, with respiratory problems leading to an important reduction in quality of life and life expectancy. We aimed to explain that the origin of chronic respiratory symptoms in patients with NI is multifactorial. AREAS COVERED: In people with NI there is a high prevalence of swallowing dysfunction and hypersalivation inducing aspiration; cough efficacy is decreased resulting in chronic lung infection; sleep-disordered breathing is frequent and muscle mass is abnormal due to malnutrition. Technical investigations are not always specific and sensitive enough to better diagnose the causes of the respiratory symptoms; moreover, they can sometimes be difficult to perform in this vulnerable patient population. We provide a clinical pathway to adopt to identify, prevent, and treat respiratory complications in children and young adults with NI. A holistic approach in discussion with all care providers and the parents is highly recommended. EXPERT OPINION: The care for people with NI and chronic respiratory problems is challenging. The interplay between several causative factors may be difficult to entangle. Well-performed clinical research in this field is largely missing and should be encouraged. Only then, evidence-based clinical care will become possible for this vulnerable patient group.

Disrupted Ca2+ homeostasis and immunodeficiency in patients with functional IP3 receptor subtype 3 defects.

Calcium signaling is essential for lymphocyte activation, with genetic disruptions of store-operated calcium (Ca2+) entry resulting in severe immunodeficiency. The inositol 1,4,5-trisphosphate receptor (IP3R), a homo- or heterotetramer of the IP3R1-3 isoforms, amplifies lymphocyte signaling by releasing Ca2+ from endoplasmic reticulum stores following antigen stimulation. Although knockout of all IP3R isoforms in mice causes immunodeficiency, the seeming redundancy of the isoforms is thought to explain the absence of variants in human immunodeficiency. In this study, we identified compound heterozygous variants of ITPR3 (a gene encoding IP3R subtype 3) in two unrelated Caucasian patients presenting with immunodeficiency. To determine whether ITPR3 variants act in a nonredundant manner and disrupt human immune responses, we characterized the Ca2+ signaling capacity, the lymphocyte response, and the clinical phenotype of these patients. We observed disrupted Ca2+ signaling in patient-derived fibroblasts and immune cells, with abnormal proliferation and activation responses following T-cell receptor stimulation. Reconstitution of IP3R3 in IP3R knockout cell lines led to the identification of variants as functional hypomorphs that showed reduced ability to discriminate between homeostatic and induced states, validating a genotype-phenotype link. These results demonstrate a functional link between defective endoplasmic reticulum Ca2+ channels and immunodeficiency and identify IP3Rs as diagnostic targets for patients with specific inborn errors of immunity. These results also extend the known cause of Ca2+-associated immunodeficiency from store-operated entry to impaired Ca2+ mobilization from the endoplasmic reticulum, revealing a broad sensitivity of lymphocytes to genetic defects in Ca2+ signaling.

Impact of COVID-19 on viral respiratory infection epidemiology in young children: A single-center analysis.

Background: The COVID-19 pandemic impacts different health aspects. Concomitant with the adoption of non-pharmaceutical interventions (NPIs) to reduce the spread of SARS-CoV-2, global surveillance studies reported a reduction in occurrence of respiratory pathogens like influenza A and B virus (IAV & IBV) and respiratory syncytial virus (RSV). We hypothesized to observe this collateral benefit on viral respiratory infection epidemiology in young children. Methods: Respiratory samples of children aged below 6 years, presenting at the outpatient clinic, emergency department, or pediatric infectious diseases department of the University Hospitals Leuven, between April 2017 and April 2021 were retrospectively analyzed. The occurrence (positivity rate), and seasonal patterns of viral respiratory infections were described. Chi-squared or Fisher's exact test (and Bonferroni correction) were used to explore differences in occurrence between 2020-2021 and previous 12-month (April to April) periods. Results: We included 3020 samples (453 respiratory panels, 2567 single SARS-CoV-2 PCR tests). IAV and IBV were not detected from March and January 2020, respectively. For IAV, positivity rate in 2020-2021 (0%, n = 0) was significantly different from 2018-2019 (12.4%, n = 17) (p < 0.001) and 2019-2020 (15.4%, n = 19) (p < 0.001). IBV positivity rate in 2020-2021 (0%, n = 0) was not significantly different from previous periods. RSV occurrence was significantly lower in 2020-2021 (3.2%, n = 3), compared to 2017-2018 (15.0%, n = 15) (p = 0.006), 2018-2019 (16.1%, n = 22) (p = 0.002) and 2019-2020 (22.8%, n = 28) (p < 0.001). The RSV (winter) peak was absent and presented later (March-April 2021). Positivity rate of parainfluenza virus 3 (PIV-3) was significantly higher in 2020-2021 (11.8%, n = 11) than 2017-2018 (1%, n = 1) (p = 0.002). PIV-3 was absent from April 2020 to January 2021, whereas no clear seasonal pattern was distinguished the other years. For the other viruses tested, no significant differences in occurrence were observed between 2020-2021 and previous periods. From March 2020 onwards, 20 cases (0.7%) of SARS-CoV-2 were identified. Conclusion: These findings reinforce the hypothesis of NPIs impacting the epidemiology of influenza viruses and RSV in young children. Compared to previous periods, no IAV and IBV cases were observed in the 2020-2021 study period, and the RSV peak occurred later. Since the pandemic is still ongoing, continuation of epidemiological surveillance, even on a larger scale, is indicated.

The Short Term Influence of Chest Physiotherapy on Lung Function Parameters in Children With Cystic Fibrosis and Primary Ciliary Dyskinesia.

Airway clearance therapy (ACT) is one of the cornerstone treatment modalities to improve mucociliary clearance for patients with bronchiectasis. The progression of lung disease in patients with bronchiectasis can be evaluated by spirometry and multiple breath washout (MBW) and it is advised to monitor these on a regular basis. However, the short term effect of ACT on spirometry and MBW parameters is insufficiently clear and this variability may impact standardization. For cystic fibrosis (CF), available literature refutes a short time effect on spirometry and MBW parameters in children, however, for primary ciliary dyskinesia (PCD) no data are available. We performed a single-center, prospective cross-over study to evaluate the short term effect of a single ACT session using positive expiratory pressure mask on forced expiratory volume in 1 s (FEV1) and lung clearance index (LCI), derived from MBW, compared to no ACT (control) in pediatric patients with CF and PCD. A total of 31 children were included: 14 with PCD and 17 with CF. For the whole group, there was no difference in median change of FEV1 pp between the treatment and the control group (p 0.969), nor in median change of LCI (p 0.294). For the CF subgroup, the mean change in FEV1 pp with ACT was -1.4% (range -9 to + 5) versus -0.2% (range -6 to + 5) for no ACT (p 0.271), the mean change in LCI with ACT was + 0.10 (range -0.7 to + 1.2) versus + 0.17 (range -0.5 to + 2.8) for no ACT (p 0.814). In the PCD subgroup, the mean change in FEV1 pp with ACT was + 1.0 (range -7 to + 8) versus -0.3 (range -6 to + 5) for no ACT (p 0.293) and the mean change in LCI with ACT was -0.46 (range -3.7 to + 0.9) versus -0.11 (range -1.4 to + 1.3) for no ACT (p 0.178). There was no difference between PCD and CF for change in FEV1 pp after ACT (p = 0.208), nor for LCI (p = 0.095). In this small group of pediatric patients, no significant short-term effect of chest physiotherapy on FEV1 pp nor LCI in PCD and CF values nor variability was documented.

Risk factors for disease severity and increased medical resource utilization in respiratory syncytial virus (+) hospitalized children: A descriptive study conducted in four Belgian hospitals.

BACKGROUND: We aimed to provide regional data on clinical symptoms, medical resource utilization (MRU), and risk factors for increased MRU in hospitalized respiratory syncytial virus (RSV)-infected Belgian pediatric population. METHODS: This prospective, multicenter study enrolled RSV (+) hospitalized children (aged ≤5y) during the 2013-2015 RSV seasons. RSV was diagnosed within 24h of hospitalization. Disease severity of RSV (+) patients was assessed until discharge or up to maximum six days using a Physical Examination Score (PES) and a derived score based on ability to feed, dyspnea and respiratory effort (PES3). MRU (concomitant medications, length of hospitalization [LOH], and oxygen supplementation) was evaluated. Kaplan-Meier survival analysis was performed to compare MRU by age and presence of risk factors for severe disease. Association between baseline covariates and MRU was analyzed using Cox regression models. RESULTS: In total, 75 children were included, Median (range) age was 4 (0-41) months, risk factors were present in 18.7%, and early hospitalization (≤3 days of symptom onset) was observed in 57.3% of patients. Cough (100%), feeding problems (82.2%), nasal discharge (87.8%), and rales and rhonchi (82.2%) were frequently observed. Median (range) LOH and oxygen supplementation was 5 (2-7) and 3 (1-7) days. Oxygen supplementation, bronchodilators, and antibiotics were administered to 58.7%, 64.0%, and 41.3% of the patients, respectively. Age <3 months and baseline total PES3 score were associated with probability and the duration of receiving oxygen supplementation. LOH was not associated with any covariate. CONCLUSION: RSV is associated with high disease burden and MRU in hospitalized children. Oxygen supplementation but not length of hospitalization was associated with very young age and the PES3 score. These results warrant further assessment of the PES3 score as a predictor for the probability of receiving and length of oxygen supplementation in RSV hospitalized children. REGISTRATION: NCT02133092.

Severity of the S1251N allele in cystic fibrosis is affected by the presence of the F508C variant in cis.

BACKGROUND: In cystic fibrosis (CF), genotype-phenotype correlation is complicated by the large number of CFTR variants, the influence of modifier genes, environmental effects, and the existence of complex alleles. We document the importance of complex alleles, in particular the F508C variant present in cis with the S1251N disease-causing variant, by detailed analysis of a patient with CF, with the [S1251N;F508]/G542X genotype and a very mild phenotype, contrasting it to that of four subjects with the [S1251N;F508C]/F508del genotype and classical CF presentation. METHODS: Genetic differences were identified by Sanger sequencing and CFTR function was quantified using rectal organoids in rectal organoid morphology analysis (ROMA) and forskolin-induced swelling (FIS) assays. CFTR variants were further characterised in CF bronchial epithelial (CFBE) cell lines. The impact of involved amino acid changes in the CFTR 3D protein structure was evaluated. RESULTS: Organoids of the patient [S1251N;F508] with mild CF phenotype confirmed the CF diagnosis but showed higher residual CFTR function compared to the four others [S1251N;F508C]. CFBE cell lines showed a decrease in [S1251N;F508C]-CFTR function but not in processing when compared to [S1251N;F508]-CFTR. Analysis of the 3D CFTR structure suggested an additive deleterious effect of the combined presence of S1251N and F508C with respect to NBD1-2 dimerisation. CONCLUSIONS: In vitro and in silico data show that the presence of F508C in cis with S1251N decreases CFTR function without affecting processing. Complex CFTR alleles play a role in clinical phenotype and their identification is relevant in the context of personalised medicine for each patient with CF.

Early SARS-CoV-2 Reinfections within 60 Days and Implications for Retesting Policies.

Illustrated by a clinical case supplemented by epidemiologic data, early reinfections with SARS-CoV-2 Omicron BA.1 after infection with Delta variant, and reinfection with Omicron BA.2 after Omicron BA.1 infection, can occur within 60 days, especially in young, unvaccinated persons. The case definition of reinfection, which influences retesting policies, should be reconsidered.

Novel CFTR modulator combinations maximise rescue of G85E and N1303K in rectal organoids.

Introduction: Cystic fibrosis (CF) is a severe monogenic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Several types of CFTR modulators (correctors/potentiators) have been developed to overcome protein dysfunction associated with these mutations. CFTR modulator therapy is now available for the major CF-causing mutations; however, 10% of people with CF remain without causal treatments. By combining investigational and market-approved CFTR modulators, we aimed to maximise functional rescue of iva-, luma- and tezacaftor refractory mutants G85E and N1303K. Methods: We used the well-established forskolin-induced swelling (FIS) in primary rectal organoids to assess responses to different CFTR corrector and potentiator types. The FIS analysis was performed with brightfield microscopy, allowing both 1-h and 24-h follow-up. Corrector and potentiator activity of elexacaftor was investigated. Results: For G85E, maximal rescue was observed by a combination of elexacaftor and corr4a. For N1303K, the quadruple combination teza-elexa-ivacaftor with apigenin was required to obtain a rescue similar to that of luma-ivacaftor rescued F508del. Elexacaftor rescued G85E and N1303K by different mechanisms, with chronic corrector effects on G85E and acute potentiation of N1303K only in the presence of ivacaftor. Synergy in N1303K rescue for iva-elexacaftor and apigenin suggests at least three potentiator mechanisms for this mutant. 24-h FIS identified ivacaftor as the main CFTR modulator for N1303K and elexacaftor and apigenin as co-potentiators. Conclusions: Novel combinations of CFTR modulators can further improve functional rescue of G85E and N1303K in rectal organoids, although for N1303K, more effective CFTR modulators are still needed.

Assays of CFTR Function In Vitro, Ex Vivo and In Vivo.

Cystic fibrosis, a multi-organ genetic disease, is characterized by abnormal function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel at the apical membrane of several epithelia. In recent years, therapeutic strategies have been developed to correct the CFTR defect. To evaluate CFTR function at baseline for diagnosis, or the efficacy of CFTR-restoring therapy, reliable tests are needed to measure CFTR function, in vitro, ex vivo and in vivo. In vitro techniques either directly or indirectly measure ion fluxes; direct measurement of ion fluxes and quenching of fluorescence in cell-based assays, change in transmembrane voltage or current in patch clamp or Ussing chamber, swelling of CFTR-containing organoids by secondary water influx upon CFTR activation. Several cell or tissue types can be used. Ex vivo and in vivo assays similarly evaluate current (intestinal current measurement) and membrane potential differences (nasal potential difference), on tissues from individual patients. In the sweat test, the most frequently used in vivo evaluation of CFTR function, chloride concentration or stimulated sweat rate can be directly measured. Here, we will describe the currently available bio-assays for quantitative evaluation of CFTR function, their indications, advantages and disadvantages, and correlation with clinical outcome measures.

Needle-free iontophoresis-driven ß-adrenergic sweat rate test.

OBJECTIVES: Two CFTR-dependent ß-adrenergic sweat rate tests applying intradermal drug injections were reported to better define diagnosis and efficacy of CFTR-directed therapies. The aim of this work was to develop and test a needle-free image-based test and to provide an accurate analysis of the responses. METHODS: The modified method was conducted by applying two successive iontophoresis sessions using the Macroduct device. Efficiency of drug delivery was tested by evaporimetry. Cholinergically stimulated sweating was evoked by pilocarpine iontophoresis. ß-adrenergically stimulated sweating was obtained by iontophoresis of isoproterenol and aminophylline in the presence of atropine and ascorbic acid. A nonlinear mixed-effects (NLME) approach was applied to model volumes of sweat and subject-specific effects displaying inter- and intra-subject variability. RESULTS: Iontophoresis provided successful transdermal delivery of all drugs, including almost neutral isoproterenol and aminophylline. Pilocarpine was used at a concentration ∼130-times lower than that used in the classical Gibson and Cooke sweat test. Addition of ascorbic acid lowered the pH of the solution, made it stable, prevented isoproterenol degradation and promoted drug iontophoresis. Maximal secretory capacity and kinetic rate of ß-adrenergic responses were blunted in CF. A cutoff of 5.2 minutes for ET50, the time to reach the half maximal secretion, discriminated CF from controls with a 100% sensitivity and specificity. Heterozygous showed an apparently reduced kinetic rate and a preserved secretory capacity. CONCLUSION: We tested a safe, well-tolerated needle-free image-based sweat test potentially applicable in children. Modelling responses by NLME allowed evaluating metrics of CFTR-dependent effects reflecting secretory capacity and kinetic rate.

Riociguat for the treatment of Phe508del homozygous adults with cystic fibrosis.

BACKGROUND: Riociguat is a first-in-class soluble guanylate cyclase stimulator for which preclinical data suggested improvements in cystic fibrosis transmembrane conductance regulator (CFTR) function. METHODS: This international, multicenter, two-part, Phase II study of riociguat enrolled adults with cystic fibrosis (CF) homozygous for Phe508del CFTR. Part 1 was a 28-day, randomized, double-blind, placebo-controlled study in participants not receiving CFTR modulator therapy. Twenty-one participants were randomized 1:2 to placebo or oral riociguat (0.5 mg three times daily [tid] for 14 days, increased to 1.0 mg tid for the subsequent 14 days). The primary and secondary efficacy endpoints were change in sweat chloride concentration and percent predicted forced expiratory volume in 1 second (ppFEV1), respectively, from baseline to Day 14 and Day 28 with riociguat compared with placebo. RESULTS: Riociguat did not alter CFTR activity (change in sweat chloride) or lung function (change in ppFEV1) at doses up to 1.0 mg tid after 28 days. The most common drug-related adverse event (AE) was headache occurring in three participants (21%); serious AEs occurred in one participant receiving riociguat (7%) and one participant receiving placebo (14%). This safety profile was consistent with the underlying disease and the known safety of riociguat for its approved indications. CONCLUSIONS: The Rio-CF study was terminated due to lack of efficacy and the changing landscape of CF therapeutic development. The current study⁠, within its limits of a small sample size, did not provide evidence that riociguat could be a valid treatment option for CF. CLINICAL TRIAL REGISTRATION NUMBER: NCT02170025.

Rectal organoid morphology analysis (ROMA) as a promising diagnostic tool in cystic fibrosis.

Diagnosing cystic fibrosis (CF) when sweat chloride is not in the CF range and less than 2 disease-causing CFTR mutations are found requires physiological CFTR assays, which are not always feasible or available. We developed a new physiological CFTR assay based on the morphological differences between rectal organoids from subjects with and without CF. In organoids from 167 subjects with and 22 without CF, two parameters derived from a semi-automated image analysis protocol (rectal organoid morphology analysis, ROMA) fully discriminated CF subjects with two disease-causing mutations from non-CF subjects (p<0.001). ROMA, feasible at all ages, can be centralised to improve standardisation.

Lung clearance index predicts pulmonary exacerbations in individuals with primary ciliary dyskinesia: a multicentre cohort study.

BACKGROUND: Lung clearance index (LCI) is a promising lung function outcome in individuals with primary ciliary dyskinesia (PCD). The impact of events clinically important for individuals with PCD, such as pulmonary exacerbations, on LCI is unknown. METHODS: We conducted an international, multicentre, observational cohort study to assess the association of LCI and risk of pulmonary exacerbation, specific changes in LCI during pulmonary exacerbation and global variability of LCI across four visits every 4 months. Ninety individuals with PCD, aged 3-41 years, underwent nitrogen multiple-breath washout (MBW) and spirometry measurements. The association of LCI and pulmonary exacerbations was assessed by Cox proportional hazards and random-effects regression models. RESULTS: We obtained 430 MBW and 427 spirometry measurements. In total, 379 person-years at risk contributed to the analysis. Per one unit increase (deterioration) in LCI, the risk of future pulmonary exacerbation increased by 13%: HR (95% CI), 1.13 (1.04 to 1.23). If LCI changed from a range of values considered normal to abnormal, the risk of future pulmonary exacerbations increased by 87%: 1.87 (1.08 to 3.23). During pulmonary exacerbations, LCI increased by 1.22 units (14.5%). After pulmonary exacerbations, LCI tended to decline. Estimates of variability in LCI suggested lower variation within individuals compared with variation between individuals. Findings were comparable for forced expiratory volume in 1 s. CONCLUSION: On a visit-to-visit basis, LCI measurement may add to the prediction of pulmonary exacerbations, the assessment of lung function decline and the potential lung function response to treatment of pulmonary exacerbations.