Rectal organoid morphology analysis (ROMA) as a novel physiological assay for diagnostic classification in cystic fibrosis.

BACKGROUND: Diagnosing cystic fibrosis (CF) is not always straightforward, in particular when sweat chloride concentration (SCC) is intermediate and <2 CF-causing CFTR variants are identified. The physiological CFTR assays proposed in the guidelines, nasal potential difference and intestinal current measurement, are not readily available nor feasible at all ages. Rectal organoid morphology analysis (ROMA) was previously shown to discriminate between organoids from subjects with and without CF based on a distinct phenotypical difference: compared with non-CF organoids, CF organoids have an irregular shape and lack a visible lumen. The current study serves to further explore the role of ROMA when a CF diagnosis is inconclusive. METHODS: Organoid morphology was analysed using the previously established ROMA protocol. Two indices were calculated: the circularity index to quantify the roundness of organoids and the intensity ratio as a measure of the presence of a central lumen. RESULTS: Rectal organoids from 116 subjects were cultured and analysed together with the 189 subjects from the previous study. ROMA almost completely discriminated between CF and non-CF. ROMA indices correlated with SCC, pancreatic status and genetics, demonstrating convergent validity. For cases with an inconclusive diagnosis according to current guidelines, ROMA provided additional diagnostic information, with a diagnostic ROMA classification for 18 of 24 (75%). DISCUSSION: ROMA provides additional information to support a CF diagnosis when SCC and genetics are insufficient for diagnostic classification. ROMA is standardised and can be centralised, allowing future inclusion in the diagnostic work-up as first-choice physiological assay in case of an unclear diagnosis.

Single-cell RNA sequencing of cystic fibrosis liver disease explants reveals endothelial complement activation.

BACKGROUND & AIMS: Cystic fibrosis (CF) is considered a multisystemic disorder in which CF-associated liver disease (CFLD) is the third most common cause of mortality. Currently, no effective treatment is available for CFLD because its pathophysiology is still unclear. Interestingly, CFLD exhibits identical vascular characteristics as non-cirrhotic portal hypertension, recently classified as porto-sinusoidal vascular disorders (PSVD). METHODS: Since endothelial cells (ECs) are an important component in PSVD, we performed single-cell RNA sequencing (scRNA-seq) on four explant livers from CFLD patients to identify differential endothelial characteristics which could contribute to the disease. We comprehensively characterized the endothelial compartment and compared it with publicly available scRNA-seq datasets from cirrhotic and healthy livers. Key gene signatures were validated ex vivo on patient tissues. RESULTS: We found that ECs from CF liver explants are more closely related to healthy than cirrhotic patients. In CF patients we also discovered a distinct population of liver sinusoidal ECs-coined CF LSECs-upregulating genes involved in the complement cascade and coagulation. Finally, our immunostainings further validated the predominant periportal location of CF LSECs. CONCLUSIONS: Our work showed novel aspects of human liver ECs at the single-cell level thereby supporting endothelial involvement in CFLD, and reinforcing the hypothesis that ECs could be a driver of PSVD. Therefore, considering the vascular compartment in CF and CFLD may help developing new therapeutic approaches for these diseases.

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.

ERS International Congress 2023: highlights from the Paediatrics Assembly.

Respiratory health in children is essential for general wellbeing and healthy development in the short and long term. It is well known that many respiratory diseases in adulthood have their origins in early life, and therefore research on prevention of respiratory diseases and management of children with respiratory diseases will benefit patients during the full life course. Scientific and clinical advances in the field of respiratory health are moving at a fast pace. This article summarises some of the highlights in paediatric respiratory medicine presented at the hybrid European Respiratory Society (ERS) International Congress 2023 which took place in Milan (Italy). Selected sessions are summarised by Early Career Members of the Paediatrics Assembly (Assembly 7) under the supervision of senior ERS officers, and cover a wide range of research areas in children, including respiratory physiology and sleep, asthma and allergy, cystic fibrosis, respiratory infection and immunology, neonatology and intensive care, respiratory epidemiology and bronchology.

A core outcome set for bronchiectasis in children and adolescents for use in clinical research: an international consensus study.

Improving the treatment of non-cystic fibrosis bronchiectasis in children and adolescents requires high-quality research with outcomes that meet study objectives and are meaningful for patients and their parents and caregivers. In the absence of systematic reviews or agreement on the health outcomes that should be measured in paediatric bronchiectasis, we established an international, multidisciplinary panel of experts to develop a core outcome set (COS) that incorporates patient and parent perspectives. We undertook a systematic review from which a list of 21 outcomes was constructed; these outcomes were used to inform the development of separate surveys for ranking by parents and patients and by health-care professionals. 562 participants (201 parents and patients from 17 countries, 361 health-care professionals from 58 countries) completed the surveys. Following two consensus meetings, agreement was reached on a ten-item COS with five outcomes that were deemed to be essential: quality of life, symptoms, exacerbation frequency, non-scheduled health-care visits, and hospitalisations. Use of this international consensus-based COS will ensure that studies have consistent, patient-focused outcomes, facilitating research worldwide and, in turn, the development of evidence-based guidelines for improved clinical care and outcomes. Further research is needed to develop validated, accessible measurement instruments for several of the outcomes in this COS.

Cystic Fibrosis Cases Missed by Newborn Bloodspot Screening-Towards a Consistent Definition and Data Acquisition.

Repeated European surveys of newborn bloodspot screening (NBS) have shown varied strategies for collecting missed cases, and information on data collection differs among countries/regions, hampering data comparison. The ECFS Neonatal Screening Working Group defined missed cases by NBS as either false negatives, protocol-related, concerning analytical issues, or non-protocol-related, concerning pre- and post-analytical issues. A questionnaire has been designed and sent to all key workers identified in each NBS programme to assess the feasibility of collecting data on missed cases, the stage of the NBS programme when the system failed, and individual patient data on each missed case.

ERS International Congress 2022: highlights from the Paediatrics Assembly.

This review has been prepared by the Early Career Members and Chairs of the European Respiratory Society (ERS) Assembly 7: Paediatrics. We here summarise the highlights of the advances in paediatric respiratory research presented at the ERS International Congress 2022. The eight scientific groups of this Assembly cover a wide range of research areas, including respiratory physiology and sleep, asthma and allergy, cystic fibrosis (CF), respiratory infection and immunology, neonatology and intensive care, respiratory epidemiology, bronchology, and lung and airway developmental biology. Specifically, we report on abstracts presented at the congress on the effect of high altitude on sleep, sleep disorders, the hypoxic challenge test, and measurements of ventilation inhomogeneity. We discuss prevention of preschool wheeze and asthma, and new asthma medications. In children with CF, we describe how to monitor the effect of CF transmembrane conductance regulator modulator therapy. We present respiratory manifestations and chronic lung disease associated with common variable immunodeficiency. Furthermore, we discuss how to monitor respiratory function in neonatal and paediatric intensive care units. In respiratory epidemiology, we present the latest news from population-based and clinical cohort studies. We also focus on innovative and interventional procedures for the paediatric airway, such as cryotherapy. Finally, we stress the importance of better understanding the molecular mechanisms underlying normal and abnormal lung development.

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.

ABCA3-related interstitial lung disease beyond infancy.

BACKGROUND: The majority of patients with childhood interstitial lung disease (chILD) caused by pathogenic variants in ATP binding cassette subfamily A member 3 (ABCA3) develop severe respiratory insufficiency within their first year of life and succumb to disease if not lung transplanted. This register-based cohort study reviews patients with ABCA3 lung disease who survived beyond the age of 1 year. METHOD: Over a 21-year period, patients diagnosed as chILD due to ABCA3 deficiency were identified from the Kids Lung Register database. 44 patients survived beyond the first year of life and their long-term clinical course, oxygen supplementation and pulmonary function were reviewed. Chest CT and histopathology were scored blindly. RESULTS: At the end of the observation period, median age was 6.3 years (IQR: 2.8-11.7) and 36/44 (82%) were still alive without transplantation. Patients who had never received supplemental oxygen therapy survived longer than those persistently required oxygen supplementation (9.7 (95% CI 6.7 to 27.7) vs 3.0 years (95% CI 1.5 to 5.0), p=0.0126). Interstitial lung disease was clearly progressive over time based on lung function (forced vital capacity % predicted absolute loss -1.1% /year) and on chest CT (increasing cystic lesions in those with repetitive imaging). Lung histology pattern were variable (chronic pneumonitis of infancy, non-specific interstitial pneumonia, and desquamative interstitial pneumonia). In 37/44 subjects, the ABCA3 sequence variants were missense variants, small insertions or deletions with in-silico tools predicting some residual ABCA3 transporter function. CONCLUSION: The natural history of ABCA3-related interstitial lung disease progresses during childhood and adolescence. Disease-modifying treatments are desirable to delay such disease course.

European survey of newborn bloodspot screening for CF: opportunity to address challenges and improve performance.

BACKGROUND: The aim of this study was to record the current status of newborn bloodspot screening (NBS) for CF across Europe and assess performance. METHODS: Survey of representatives of NBS for CF programmes across Europe. Performance was assessed through a framework developed in a previous exercise. RESULTS: In 2022, we identified 22 national and 34 regional programmes in Europe. Barriers to establishing NBS included cost and political inertia. Performance was assessed from 2019 data reported by 21 national and 21 regional programmes. All programmes employed different protocols, with IRT-DNA the most common strategy. Six national and 11 regional programmes did not use DNA analysis. CONCLUSIONS: Integrating DNA analysis into the NBS protocol improves PPV, but at the expense of increased carrier and CFSPID recognition. Some programmes employ strategies to mitigate these outcomes. Programmes should constantly strive to improve performance but large datasets are needed to assess outcomes reliably.

Laboratory biomarkers in the diagnosis and follow-up of treatment of allergic bronchopulmonary aspergillosis in cystic fibrosis.

Allergic bronchopulmonary aspergillosis (ABPA), a severe inflammatory respiratory disease, is caused by a hypersensitivity reaction to the colonization of the airways with Aspergillus fumigatus. It is most often described in patients with asthma or cystic fibrosis. The diagnosis of ABPA is based on a combination of clinical, radiological, and immunological findings that have been included in different diagnostic criteria over the years. In this paper, we review the biomarkers included in these diagnostic criteria and novel research biomarkers that may be used in the diagnosis and treatment follow-up of ABPA in cystic fibrosis.

The burden and surveillance of RSV disease in young children in Belgium-expert opinion.

Infections with respiratory syncytial virus (RSV) can cause severe disease. In young children, RSV is the most common cause of lower respiratory tract illness and life-threatening infections most commonly occur in the first years of life. In adults, elderly and immunocompromised people are most vulnerable. Recently there has been an acceleration in the development of candidate RSV vaccines, monoclonal antibodies and therapeutics which are expected to become available in Europe within the next 2-10 years. Understanding the true burden of childhood RSV disease will become very important to support public health authorities and policy makers in the assessment of new therapeutic opportunities against RSV disease. A systematic literature search was performed to map local data on the burden of RSV disease and to evaluate available RSV surveillance systems. A group of 9 paediatric infectious diseases specialists participated in an expert panel. The purpose of this meeting was to evaluate and map the burden associated with RSV infection in children, including patient pathways and the epidemiological patterns of virus circulation in Belgium. Sources of information on the burden of RSV disease in Belgium are very limited. For the outpatient setting, it is estimated that 5-10% of young patients seen in primary care are referred to the hospital. Around 3500 children between 0 and 12 months of age are hospitalized for RSV-bronchiolitis every year and represent the majority of all hospitalizations. The current Belgian RSV surveillance system was evaluated and found to be insufficient. Knowledge gaps are highlighted and future perspectives and priorities offered. CONCLUSION: The Belgian population-based RSV surveillance should be improved, and a hospital-led reporting system should be put in place to enable the evaluation of the true burden of RSV disease in Belgium and to improve disease management in the future. WHAT IS KNOWN: • RSV bronchiolitis is a very important cause of infant hospitalization. • The burden of disease in the community is poorly studied and underestimated. WHAT IS NEW: • This expert opinion summarizes knowledge gaps and offers insights that allow improvement of local surveillance systems in order to establish a future-proof RSV surveillance system.

Congenital cystic adenomatoid malformations of the lung: a retrospective study of diagnosis, treatment strategy and postoperative morbidity in surgically treated patients.

OBJECTIVES: The purpose of this study was to evaluate the diagnosis of, clinical signs of and strategy for congenital cystic adenomatoid malformations (CCAM). METHODS: In this retrospective study, patients who had thoracic surgery for CCAM lesions at the University Hospitals of Leuven from July 1993 to July 2016 were identified. Data on diagnosis, prenatal ultrasound findings, clinical signs, lesion site, CCAM type, associated anomalies, imaging, surgical approach and postoperative morbidity were reviewed. The Fisher exact and Mann-Whitney tests were used as appropriate. RESULTS: A total of 55 patients were identified with CCAM. In 65% (n = 36/55), CCAM was detected on prenatal ultrasound scans. Prenatal symptoms due to hydrops or mass effect were present in 22% (n = 8/36), 6 of whom eventually needed prenatal intervention (thoracoamniotic shunting or intrauterine puncture). Elective surgery was performed in 40% of patients (n = 22/55); others developed clinical signs that indicated the need for semi-urgent surgery, with clinical signs of pulmonary infection and respiratory distress being the most common. Most patients had a single lobectomy via a minithoracotomy. Postoperative complications and length of stay were significantly higher in patients with CCAM with preoperative clinical signs. CONCLUSIONS: Surgery in asymptomatic patients with CCAM can be performed safely with few postoperative complications and can be planned at a young age in patients with a high risk of developing clinical signs later in life.

The Management of Asymptomatic Congenital Pulmonary Airway Malformation: Results of a European Delphi Survey.

Consensus on the optimal management of asymptomatic congenital pulmonary airway malformation (CPAM) is lacking, and comparison between studies remains difficult due to a large variety in outcome measures. We aimed to define a core outcome set (COS) for pediatric patients with an asymptomatic CPAM. An online, three-round Delphi survey was conducted in two stakeholder groups of specialized caregivers (surgeons and non-surgeons) in various European centers. Proposed outcome parameters were scored according to level of importance, and the final COS was established through consensus. A total of 55 participants (33 surgeons, 22 non-surgeons) from 28 centers in 13 European countries completed the three rounds and rated 43 outcome parameters. The final COS comprises seven outcome parameters: respiratory insufficiency, surgical complications, mass effect/mediastinal shift (at three time-points) and multifocal disease (at two time-points). The seven outcome parameters included in the final COS reflect the diversity in priorities among this large group of European participants. However, we recommend the incorporation of these outcome parameters in the design of future studies, as they describe measurable and validated outcomes as well as the accepted age at measurement.

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.

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.

European Respiratory Society statement for defining respiratory exacerbations in children and adolescents with bronchiectasis for clinical trials.

Bronchiectasis is being diagnosed increasingly in children and adolescents. Recurrent respiratory exacerbations are common in children and adolescents with this chronic pulmonary disorder. Respiratory exacerbations are associated with an impaired quality of life, poorer long-term clinical outcomes, and substantial costs to the family and health systems. The 2021 European Respiratory Society (ERS) clinical practice guideline for the management of children and adolescents with bronchiectasis provided a definition of acute respiratory exacerbations for clinical use but to date there is no comparable universal definition for clinical research. Given the importance of exacerbations in the field, this ERS Task Force sought to obtain robust definitions of respiratory exacerbations for clinical research. The panel was a multidisciplinary team of specialists in paediatric and adult respiratory medicine, infectious disease, physiotherapy, primary care, nursing, radiology, methodology, patient advocacy, and parents of children and adolescents with bronchiectasis. We used a standardised process that included a systematic literature review, parent survey, and a Delphi approach involving 299 physicians (54 countries) caring for children and adolescents with bronchiectasis. Consensus was obtained for all four statements drafted by the panel as the disagreement rate was very low (range 3.6-7.2%). The panel unanimously endorsed the four consensus definitions for 1a) non-severe exacerbation and 1b) severe exacerbation as an outcome measure, 2) non-severe exacerbation for studies initiating treatment, and 3) resolution of a non-severe exacerbation for clinical trials involving children and adolescents with bronchiectasis. This ERS Task Force proposes using these internationally derived, consensus-based definitions of respiratory exacerbations for future clinical paediatric bronchiectasis research.

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.