Combined approaches, including long-read sequencing, address the diagnostic challenge of HYDIN in primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD), a disorder of the motile cilia, is now recognised as an underdiagnosed cause of bronchiectasis. Accurate PCD diagnosis comprises clinical assessment, analysis of cilia and the identification of biallelic variants in one of 50 known PCD-related genes, including HYDIN. HYDIN-related PCD is underdiagnosed due to the presence of a pseudogene, HYDIN2, with 98% sequence homology to HYDIN. This presents a significant challenge for Short-Read Next Generation Sequencing (SR-NGS) and analysis, and many diagnostic PCD gene panels do not include HYDIN. We have used a combined approach of SR-NGS with bioinformatic masking of HYDIN2, and state-of-the-art long-read Nanopore sequencing (LR_NGS), together with analysis of respiratory cilia including transmission electron microscopy and immunofluorescence to address the underdiagnosis of HYDIN as a cause of PCD. Bioinformatic masking of HYDIN2 after SR-NGS facilitated the detection of biallelic HYDIN variants in 15 of 437 families, but compromised the detection of copy number variants. Supplementing testing with LR-NGS detected HYDIN deletions in 2 families, where SR-NGS had detected a single heterozygous HYDIN variant. LR-NGS was also able to confirm true homozygosity in 2 families when parental testing was not possible. Utilising a combined genomic diagnostic approach, biallelic HYDIN variants were detected in 17 families from 242 genetically confirmed PCD cases, comprising 7% of our PCD cohort. This represents the largest reported HYDIN cohort to date and highlights previous underdiagnosis of HYDIN-associated PCD. Moreover this provides further evidence for the utility of LR-NGS in diagnostic testing, particularly for regions of high genomic complexity.

A BEAT-PCD consensus statement: a core outcome set for pulmonary disease interventions in primary ciliary dyskinesia.

Background: Consistent use of reliable and clinically appropriate outcome measures is a priority for clinical trials, with clear definitions to allow comparability. We aimed to develop a core outcome set (COS) for pulmonary disease interventions in primary ciliary dyskinesia (PCD). Methods: A multidisciplinary international PCD expert panel was set up. A list of outcomes was created based on published literature. Using a modified three-round e-Delphi technique, the panel was asked to decide on relevant end-points related to pulmonary disease interventions and how they should be reported. First, inclusion of an outcome in the COS was determined. Second, the minimum information that should be reported per outcome. The third round finalised statements. Consensus was defined as ≥80% agreement among experts. Results: During the first round, experts reached consensus on four out of 24 outcomes to be included in the COS. Five additional outcomes were discussed in subsequent rounds for their use in different subsettings. Consensus on standardised methods of reporting for the COS was reached. Spirometry, health-related quality-of-life scores, microbiology and exacerbations were included in the final COS. Conclusion: This expert consensus resulted in a COS for clinical trials on pulmonary health among people with PCD.

Ultrastructural cilia defects in multi-ciliated uterine glandular epithelial cells from women with reproductive failure.

In brief: The causes of subfertility and recurrent pregnancy loss are often unclear. This study shows that endometrial gland cilia from women with subfertility have ultrastructural defects. Abstract: Endometrial glands secrete products into the endometrium and are necessary for embryo implantation and successful pregnancy. However, structural and functional abnormalities in endometrial gland cilia from women with reproductive failure remain poorly understood. This was a cross-sectional study where endometrial biopsies were collected at days 19-23 of the menstrual cycle from women with unexplained recurrent pregnancy loss (n = 15), unexplained subfertility (n = 11) or from egg donor control participants (n = 10). Endometrial gland cilia ultrastructure was imaged by transmission electron microscopy and cilia defects assessed by an electron-microscopist from a national primary ciliary dyskinesia diagnostic centre. Endometrial glands were isolated, and the cilia beat frequency recorded by high speed video. Subfertile women have proportionately lower ultrastructurally normal cilia (P < 0.05); higher frequency of absent dynamin arms (P < 0.01) or inner arm defects (P < 0.01) and lower cilia beat frequency (P < 0.05). The mechanisms underlying these obversions have yet to be determined. Recent studies have identified cilia related gene expression changes associated with reproductive failure and this study adds to the growing body of literature revealing structural and functional changes. The observation that cilia defects occurred at a higher frequency in endometrial glands of subfertile women raises the question of its mechanistic role in implantation.

Incidence and Severity of SARS-CoV-2 Infections in People With Primary Ciliary Dyskinesia.

Objectives: There is little data on SARS-CoV-2 in people with rare chronic diseases. We studied incidence and severity of SARS-CoV-2 and its risk factors in people with primary ciliary dyskinesia (PCD) from May 2020 to May 2022. Methods: We used self-reported questionnaire data from the COVID-PCD study at baseline or during weekly follow-ups. We studied factors associated with SARS-CoV-2 and symptoms using Poisson regression. Results: By May 2022, 728 people participated (40% male, median age 27 years; range 0-85). 87 (12%) reported SARS-CoV-2 at baseline or during follow-up and 62 people reported an incident SARS-CoV-2 infection during 716 person-years (incidence rate 9 per 100 person years). The strongest predictors for reporting SARS-CoV-2 were exposure during periods where Delta variant was dominant (IRR 4.52, 95% CI 1.92-10.6) and Omicron variants (IRR 13.3, 95% CI 5.2-33.8). Severity was mild; 12 (14%) were asymptomatic and 75 (86%) had symptoms among whom four were hospitalized. None needed intensive care and nobody died. Conclusion: The COVID-PCD study participants did not have a higher incidence of SARS-CoV-2 infections nor higher risk of severe COVID-19 disease than people from the general population.

Diagnostic testing in people with primary ciliary dyskinesia: An international participatory study.

Diagnostic tests are important in primary ciliary dyskinesia (PCD), a rare disease, to confirm the diagnosis and characterize the disease. We compared diagnostic tests for PCD between countries worldwide, assessed whether people with PCD recall their tests, and identified factors associated with the use of tests. We used cross-sectional data from COVID-PCD-an international participatory cohort study collecting information directly from people with PCD. The baseline questionnaire inquired about tests used for PCD diagnosis. Using logistic regression, we investigated factors associated with measurement of nasal nitric oxide (nNO), biopsy for electron or video microscopy, and genetic testing. We included data from 747 participants (60% females) from 49 countries worldwide with median age 27 (interquartile range 12-44). Most (92%) reported diagnostic tests for PCD. Participants reported measurements of nNO (342; 49%), biopsy samples (561; 75%), and genetic tests (435; 58%). The reported use of individual tests, such as genetics, varied between countries from 38% in Switzerland to 68% in North America. Participant recall of test type also differed between countries with lowest recall in Switzerland. One-third (232; 36%) of participants reported all three tests (nNO, biopsy, and genetics). Recently diagnosed people reported more tests [nNO odds ratio (OR) 2.2, 95% Confidence Interval (CI) 1.5-3.2; biopsy OR 3.2, 95%CI 2.1-4.9; genetics OR 4.7, 95%CI 3.2-6.9] and those with situs abnormalities fewer tests (nNO OR 0.5, 95%CI 0.4-0.7; biopsy OR 0.5, 95%CI 0.4-0.8; genetics OR 0.7, 95%CI 0.5-0.94). Our results indicate PCD diagnostic testing differed widely around the world and many patients received incomplete diagnostic work-up based only on clinical features or single tests. People diagnosed long ago and those with situs abnormalities possibly benefit from supplementary testing to refine their diagnosis as a prerequisite for personalized medicine.

Defective airway intraflagellar transport underlies a combined motile and primary ciliopathy syndrome caused by IFT74 mutations.

Ciliopathies are inherited disorders caused by defective cilia. Mutations affecting motile cilia usually cause the chronic muco-obstructive sinopulmonary disease primary ciliary dyskinesia (PCD) and are associated with laterality defects, while a broad spectrum of early developmental as well as degenerative syndromes arise from mutations affecting signalling of primary (non-motile) cilia. Cilia assembly and functioning requires intraflagellar transport (IFT) of cargos assisted by IFT-B and IFT-A adaptor complexes. Within IFT-B, the N-termini of partner proteins IFT74 and IFT81 govern tubulin transport to build the ciliary microtubular cytoskeleton. We detected a homozygous 3-kb intragenic IFT74 deletion removing the exon 2 initiation codon and 40 N-terminal amino acids in two affected siblings. Both had clinical features of PCD with bronchiectasis, but no laterality defects. They also had retinal dysplasia and abnormal bone growth, with a narrowed thorax and short ribs, shortened long bones and digits, and abnormal skull shape. This resembles short-rib thoracic dysplasia, a skeletal ciliopathy previously linked to IFT defects in primary cilia, not motile cilia. Ciliated nasal epithelial cells collected from affected individuals had reduced numbers of shortened motile cilia with disarranged microtubules, some misorientation of the basal feet, and disrupted cilia structural and IFT protein distributions. No full-length IFT74 was expressed, only truncated forms that were consistent with N-terminal deletion and inframe translation from downstream initiation codons. In affinity purification mass spectrometry, exon 2-deleted IFT74 initiated from the nearest inframe downstream methionine 41 still interacts as part of the IFT-B complex, but only with reduced interaction levels and not with all its usual IFT-B partners. We propose that this is a hypomorphic mutation with some residual protein function retained, which gives rise to a primary skeletal ciliopathy combined with defective motile cilia and PCD.

Ear and upper airway clinical outcome measures for use in primary ciliary dyskinesia research: a scoping review.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterised by pulmonary, otological and sino-nasal manifestations. Well-defined clinical outcome measures are needed in such rare diseases research to improve follow-up and treatments. Pulmonary outcome measures have recently been described. The aim of this study was to identify ear and upper airway outcome measures that could be used for longitudinal follow-up of individuals with PCD. METHODS: A scoping review was performed by systematically searching MEDLINE, Embase and Cochrane Database of Systematic Reviews online databases for studies published from January 1996 to March 2022 that included at least 10 adult or paediatric PCD patients and reported ear and upper airway outcomes. RESULTS: 33 studies (1794 patients) were included. 10 ear and upper airway outcomes were reported. 17 studies reported audiometry, 16 reported otoscopic findings, and 13 reported rhinoscopic findings and sinus imaging. Health-related quality of life questionnaires were performed in seven studies. There was a high variability in definitions and measurement of outcomes between studies. CONCLUSIONS: This scoping review highlights the lack of data regarding ear and upper airway outcomes in PCD. It also reports a high heterogeneity in outcome definitions or measures. We provide well-founded specific suggestions to standardise ear and upper airway outcome definitions and reporting for future PCD research studies.

The Palestinian primary ciliary dyskinesia population: first results of the diagnostic and genetic spectrum.

Background: Diagnostic testing for primary ciliary dyskinesia (PCD) started in 2013 in Palestine. We aimed to describe the diagnostic, genetic and clinical spectrum of the Palestinian PCD population. Methods: Individuals with symptoms suggestive of PCD were opportunistically considered for diagnostic testing: nasal nitric oxide (nNO) measurement, transmission electron microscopy (TEM) and/or PCD genetic panel or whole-exome testing. Clinical characteristics of those with a positive diagnosis were collected close to testing including forced expiratory volume in 1 s (FEV1) Global Lung Index z-scores and body mass index z-scores. Results: 68 individuals had a definite positive PCD diagnosis, 31 confirmed by genetic and TEM results, 23 by TEM results alone, and 14 by genetic variants alone. 45 individuals from 40 families had 17 clinically actionable variants and four had variants of unknown significance in 14 PCD genes. CCDC39, DNAH11 and DNAAF11 were the most commonly mutated genes. 100% of variants were homozygous. Patients had a median age of 10.0 years at diagnosis, were highly consanguineous (93%) and 100% were of Arabic descent. Clinical features included persistent wet cough (99%), neonatal respiratory distress (84%) and situs inversus (43%). Lung function at diagnosis was already impaired (FEV1 z-score median -1.90 (-5.0-1.32)) and growth was mostly within the normal range (z-score mean -0.36 (-3.03-2.57). 19% individuals had finger clubbing. Conclusions: Despite limited local resources in Palestine, detailed geno- and phenotyping forms the basis of one of the largest national PCD populations globally. There was notable familial homozygosity within the context of significant population heterogeneity.

The impact of primary ciliary dyskinesia on female and male fertility: a narrative review.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a genetic condition affecting the structure and function of sperm flagellum and motile cilia including those in the male and female reproductive tracts. Infertility is a commonly reported feature of PCD, but there is uncertainty as to how best to counsel patients on their fertility prognosis. OBJECTIVE AND RATIONALE: This review aimed to summarize the prevalence of subfertility, possible underlying mechanisms, and the success of ART in men and women with PCD. The efficacy of ART in this patient group is relatively unknown and, hence, the management of infertility in PCD patients remains a challenge. There are no previous published or registered systematic reviews of fertility outcomes in PCD. SEARCH METHODS: Systematic literature searches were performed in Medline, Embase, Cochrane Library, and PubMed electronic databases to identify publications between 1964 and 2022 reporting fertility outcomes in men and women with PCD. Publications were excluded if they reported only animal studies, where gender was not specified or where subjects had a medical co-morbidity also known to impact fertility. Quality of evidence was assessed by critical appraisal and application of an appraisal tool for cross-sectional studies. The primary outcomes were natural conception in men and women with PCD, and conception following ART in men and women with PCD. OUTCOMES: A total of 1565 publications were identified, and 108 publications were included after screening by two independent researchers. The quality of available evidence was low. The exact prevalence of subfertility in PCD is unclear but appears to be higher in men (up to 83% affected) compared to women (up to 61% affected). Variation in the prevalence of subfertility was observed between geographic populations which may be explained by differences in underlying genotype and cilia function. Limited evidence suggests subfertility in affected individuals is likely caused by abnormal cilia motion in the fallopian tubes, endometrium and efferent ductules, and dysmotile sperm. Some men and women with PCD benefited from ART, which suggests its use should be considered in the management of subfertility in this patient group. Further epidemiological and controlled studies are needed to determine the predictors of fertility and optimal management in this patient group. WIDER IMPLICATIONS: It is important that patients with PCD receive evidence-based counselling about the potential impact of their condition on their fertility prognosis and what management options may be available to them if affected. Understanding the pathophysiology and optimal management of subfertility in PCD will increase our understanding of the role of cilia and the impact of wider secondary ciliopathies on reproduction.

Nasal nitric oxide measurement in children for the diagnosis of primary ciliary dyskinesia: European Respiratory Society technical standard.

Nasal nitric oxide (nNO) is extremely low in most people with primary ciliary dyskinesia (PCD) and its measurement is an important contributor to making the diagnosis. Existing guidelines and technical standards focus on nNO measurements in older, cooperative children using chemiluminescence analysers. However, measurements of nNO in pre-school-age children (age 2-5 years) may facilitate early diagnosis and electrochemical rather than chemiluminescence analysers are widely used. Pre-schoolers often need different methods to be employed when measuring nNO. Hence, a European Respiratory Society Task Force has developed this technical standard as the first step towards standardising sampling, analysis and reporting of nNO measured as part of the diagnostic testing for PCD in all age groups, including pre-school-age children. Furthermore, we considered both chemiluminescence and electrochemical analysers that are in use worldwide. There was a paucity of quality evidence for electrochemical analysers and sampling methods used in young children, and the Task Force proposes future research priorities to allow updates of this technical standard.

Biallelic variants in CEP164 cause a motile ciliopathy-like syndrome.

Ciliopathies may be classed as primary or motile depending on the underlying ciliary defect and are usually considered distinct clinical entities. Primary ciliopathies are associated with multisystem syndromes typically affecting the brain, kidney, and eye, as well as other organ systems such as the liver, skeleton, auditory system, and metabolism. Motile ciliopathies are a heterogenous group of disorders with defects in specialised motile ciliated tissues found within the lung, brain, and reproductive system, and are associated with primary ciliary dyskinesia, bronchiectasis, infertility and rarely hydrocephalus. Primary and motile cilia share defined core ultra-structures with an overlapping proteome, and human disease phenotypes can reflect both primary and motile ciliopathies. CEP164 encodes a centrosomal distal appendage protein vital for primary ciliogenesis. Human CEP164 mutations are typically described in patients with nephronophthisis-related primary ciliopathies but have also been implicated in motile ciliary dysfunction. Here we describe a patient with an atypical motile ciliopathy phenotype and biallelic CEP164 variants. This work provides further evidence that CEP164 mutations can contribute to both primary and motile ciliopathy syndromes, supporting their functional and clinical overlap, and informs the investigation and management of CEP164 ciliopathy patients.

The Impact on Parents of Diagnosing PCD in Young Children.

Primary ciliary dyskinesia (PCD) is an incurable, rare, inherited, chronic condition. Treatment includes the regular clearing of airway mucus, aggressive treatment of infections and management of hearing loss. Caregiver burden has not been explored, hence we interviewed 18 mothers and 6 fathers of children under 6 years to understand the impact of diagnostic testing and implications of a positive diagnosis. Interviews were transcribed and thematically analysed and five key themes were identified. These included the parents' experiences following child's diagnosis, impact of child's treatment regimen on parent, impact of child's health status on parent, parent's coping strategies, and parental concerns for the future. Parents described their diagnostic journey, with the findings revealing how a lack of awareness among clinicians of the PCD symptom pattern can lead to a delayed diagnosis. Parents discussed the emotional and practical impact of a PCD diagnosis and the coping strategies employed to deal with challenges arising following a diagnosis. Parents use a variety of different lifestyle changes to accommodate their child's treatment regimen and to cope with disruptive life events such as the COVID-19 pandemic. This study provides valuable insights into parental adjustment and adaptation to a PCD diagnosis and management regimen. Going forward, this research highlights the need for integrated social care for PCD patients and their families.

Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding.

Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.

Temporal Whole-Transcriptomic Analysis of Characterized In Vitro and Ex Vivo Primary Nasal Epithelia.

Air-liquid interface (ALI) cell culture of primary airway progenitors enables the differentiation and recapitulation of a pseudostratified epithelium in vitro, providing a highly useful tool for researching respiratory health and disease. Previous studies into gene expression in ALI-cultures compared to ex vivo nasal brushings have been limited in the number of time-points and/or the number of genes studied. In this study physiological and global transcriptomic changes were assessed in an extended in vitro 63-day human healthy nasal epithelium ALI-culture period and compared to ex vivo nasal brushing samples. Ex vivo nasal brushing samples formed distinct transcriptome clusters to in vitro ALI-cultured nasal epithelia, with from day 14 onwards ALI samples best matching the ex vivo samples. Immune response regulation genes were not expressed in the in vitro ALI-culture compared to the ex vivo nasal brushing samples, likely because the in vitro cultures lack an airway microbiome, lack airborne particles stimulation, or did not host an immune cell component. This highlights the need for more advanced co-cultures with immune cell representation to better reflect the physiological state. During the first week of ALI-culture genes related to metabolism and proliferation were increased. By the end of week 1 epithelial cell barrier function plateaued and multiciliated cell differentiation started, although widespread ciliation was not complete until day 28. These results highlight that time-points at which ALI-cultures are harvested for research studies needs to be carefully considered to suit the purpose of investigation (transcriptomic and/or functional analysis).

Evaluating the Immune Response in Treatment-Naive Hospitalised Patients With Influenza and COVID-19.

The worldwide COVID-19 pandemic has claimed millions of lives and has had a profound effect on global life. Understanding the body's immune response to SARS-CoV-2 infection is crucial in improving patient management and prognosis. In this study we compared influenza and SARS-CoV-2 infected patient cohorts to identify distinct blood transcript abundances and cellular composition to better understand the natural immune response associated with COVID-19, compared to another viral infection being influenza, and identify a prognostic signature of COVID-19 patient outcome. Clinical characteristics and peripheral blood were acquired upon hospital admission from two well characterised cohorts, a cohort of 88 patients infected with influenza and a cohort of 80 patients infected with SARS-CoV-2 during the first wave of the pandemic and prior to availability of COVID-19 treatments and vaccines. Gene transcript abundances, enriched pathways and cellular composition were compared between cohorts using RNA-seq. A genetic signature between COVID-19 survivors and non-survivors was assessed as a prognostic predictor of COVID-19 outcome. Contrasting immune responses were detected with an innate response elevated in influenza and an adaptive response elevated in COVID-19. Additionally ribosomal, mitochondrial oxidative stress and interferon signalling pathways differentiated the cohorts. An adaptive immune response was associated with COVID-19 survival, while an inflammatory response predicted death. A prognostic transcript signature, associated with circulating immunoglobulins, nucleosome assembly, cytokine production and T cell activation, was able to stratify COVID-19 patients likely to survive or die. This study provides a unique insight into the immune responses of treatment naïve patients with influenza or COVID-19. The comparison of immune response between COVID-19 survivors and non-survivors enables prognostication of COVID-19 patients and may suggest potential therapeutic strategies to improve survival.

Genome sequencing reveals underdiagnosis of primary ciliary dyskinesia in bronchiectasis.

BACKGROUND: Bronchiectasis can result from infectious, genetic, immunological and allergic causes. 60-80% of cases are idiopathic, but a well-recognised genetic cause is the motile ciliopathy, primary ciliary dyskinesia (PCD). Diagnosis of PCD has management implications including addressing comorbidities, implementing genetic and fertility counselling and future access to PCD-specific treatments. Diagnostic testing can be complex; however, PCD genetic testing is moving rapidly from research into clinical diagnostics and would confirm the cause of bronchiectasis. METHODS: This observational study used genetic data from severe bronchiectasis patients recruited to the UK 100,000 Genomes Project and patients referred for gene panel testing within a tertiary respiratory hospital. Patients referred for genetic testing due to clinical suspicion of PCD were excluded from both analyses. Data were accessed from the British Thoracic Society audit, to investigate whether motile ciliopathies are underdiagnosed in people with bronchiectasis in the UK. RESULTS: Pathogenic or likely pathogenic variants were identified in motile ciliopathy genes in 17 (12%) out of 142 individuals by whole-genome sequencing. Similarly, in a single centre with access to pathological diagnostic facilities, 5-10% of patients received a PCD diagnosis by gene panel, often linked to normal/inconclusive nasal nitric oxide and cilia functional test results. In 4898 audited patients with bronchiectasis, <2% were tested for PCD and <1% received genetic testing. CONCLUSIONS: PCD is underdiagnosed as a cause of bronchiectasis. Increased uptake of genetic testing may help to identify bronchiectasis due to motile ciliopathies and ensure appropriate management.

An international survey on nasal nitric oxide measurement practices for the diagnosis of primary ciliary dyskinesia.

Nasal nitric oxide (nNO) measurements are used in the assessment of patients suspected of having primary ciliary dyskinesia (PCD), but recommendations for performing such measurements have not focused on children and do not include all current practices. To guide the development of a European Respiratory Society-supported technical standard for nNO measurement in children, an international online survey was conducted to better understand current measurement practices among providers involved in PCD diagnostics. 78 professionals responded, representing 65 centres across 18 countries, mainly in Europe and North America. Nearly all centres measured nNO in children and more than half performed measurements before 5 years of age. The test was often postponed in children with signs of acute airway infection. In Europe, the electrochemical technique was more frequently used than chemiluminescence. A similar proportion of centres performed measurements during exhalation against a resistance (49 out of 65) or during tidal breathing (50 out of 65); 15 centres used only exhalation against a resistance and 15 used only tidal breathing. The cut-off values used to discriminate PCD were consistent across centres using chemiluminescence analysers; these centres reported results as an output (nL·min-1). Cut-off values were highly variable across centres using electrochemical devices, and nNO concentrations were typically reported as ppb. This survey is the first to determine real-world use of nNO measurements globally and revealed remarkable variability in methodology, equipment and interpretation. These findings will help standardise methods and training.

Lung function from school age to adulthood in primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) presents with symptoms early in life and the disease course may be progressive, but longitudinal data on lung function are scarce. This multinational cohort study describes lung function trajectories in children, adolescents and young adults with PCD. We analysed data from 486 patients with repeated lung function measurements obtained between the age of 6 and 24 years from the International PCD Cohort and calculated z-scores for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio using the Global Lung Function Initiative 2012 references. We described baseline lung function and change of lung function over time and described their associations with possible determinants in mixed-effects linear regression models. Overall, FEV1, FVC and FEV1/FVC z-scores declined over time (average crude annual FEV1 decline was -0.07 z-scores), but not at the same rate for all patients. FEV1 z-scores improved over time in 21% of patients, remained stable in 40% and declined in 39%. Low body mass index was associated with poor baseline lung function and with further decline. Results differed by country and ultrastructural defect, but we found no evidence of differences by sex, calendar year of diagnosis, age at diagnosis, diagnostic certainty or laterality defect. Our study shows that on average lung function in PCD declines throughout the entire period of lung growth, from childhood to young adult age, even among patients treated in specialised centres. It is essential to develop strategies to reverse this tendency and improve prognosis.

Lower airway clinical outcome measures for use in primary ciliary dyskinesia research: a scoping review.

OBJECTIVES: Disease-specific, well-defined and validated clinical outcome measures are essential in designing research studies. Poorly defined outcome measures hamper pooling of data and comparisons between studies. We aimed to identify and describe pulmonary outcome measures that could be used for follow-up of patients with primary ciliary dyskinesia (PCD). METHODS: We conducted a scoping review by systematically searching MEDLINE, Embase and the Cochrane Database of Systematic Reviews online databases for studies published from 1996 to 2020 that included ≥10 PCD adult and/or paediatric patients. RESULTS: We included 102 studies (7289 patients). 83 studies reported on spirometry, 11 on body plethysmography, 15 on multiple-breath washout, 36 on high-resolution computed tomography (HRCT), 57 on microbiology and 17 on health-related quality of life. Measurement and reporting of outcomes varied considerably between studies (e.g. different scoring systems for chest HRCT scans). Additionally, definitions of outcome measures varied (e.g. definition of chronic colonisation by respiratory pathogen), impeding direct comparisons of results. CONCLUSIONS: This review highlights the need for standardisation of measurements and reporting of outcome measures to enable comparisons between studies. Defining a core set of clinical outcome measures is necessary to ensure reproducibility of results and for use in future trials and prospective cohorts.