Analyses of 1,236 genotyped primary ciliary dyskinesia individuals identify regional clusters of distinct DNA variants and significant genotype-phenotype correlations.

BACKGROUND: Primary ciliary dyskinesia (PCD) represents a group of rare hereditary disorders characterized by deficient ciliary airway clearance that can be associated with laterality defects. We aimed to describe the underlying gene defects, geographical differences in genotypes and their relationship to diagnostic findings and clinical phenotypes. METHODS: Genetic variants and clinical findings (age, sex, body mass index, laterality defects, FEV1) were collected from 19 countries using the ERN LUNG International PCD Registry. Genetic data were evaluated according to ACMG guidelines. We assessed regional distribution of implicated genes and genetic variants as well as genotype correlations with laterality defects and FEV1. RESULTS: 1236 individuals carried 908 distinct pathogenic DNA variants in 46 PCD genes. We found considerable variation in the distribution of PCD genotypes across countries due to the presence of distinct founder variants. The prevalence of PCD genotypes associated with pathognomonic ultrastructural defects (mean 72%; 47-100%) and laterality defects (mean 42%; 28-69%) varied widely among the countries. The prevalence of laterality defects was significantly lower in PCD individuals without pathognomonic ciliary ultrastructure defects (18%). The PCD cohort had a reduced median FEV1 z-score (-1.66). In the group of individuals with CCNO (-3.26), CCDC39 (-2.49), and CCDC40 (-2.96) variants, FEV1 z-scores were significantly lower, while the group of DNAH11 (-0.83) and ODAD1 (-0.85) variant individuals had significantly milder FEV1 z-score reductions compared to the whole PCD cohort. CONCLUSION: This unprecedented multinational dataset of DNA variants and information on their distribution across countries facilitates interpretation of genetic epidemiology of PCD and provides prediction of diagnostic and phenotypic features such as the course of lung function.

Danish Drowning Formula for identification of out-of-hospital cardiac arrest from drowning.

BACKGROUND: Accurate, reliable, and sufficient data is required to reduce the burden of drowning by targeting preventive measures and improving treatment. Today's drowning statistics are informed by various methods sometimes based on data sources with questionable reliability. These methods are likely responsible for a systematic and significant underreporting of drowning. This study's aim was to assess the 30-day survival of patients with out-of-hospital cardiac arrest (OHCA) identified in the Danish Cardiac Arrest Registry (DCAR) after applying the Danish Drowning Formula. METHODS: This nationwide, cohort, registry-based study with 30-day follow-up used the Danish Drowning Formula to identify drowning-related OHCA with a resuscitation attempt from the DCAR from January 1st, 2016, through December 31st, 2021. The Danish Drowning Formula is a text-search algorithm constructed for this study based on trigger-words identified from the prehospital medical records of validated drowning cases. The primary outcome was 30-day survival from OHCA. Data were analyzed using multiple logistic regression. RESULTS: Drowning-related OHCA occurred in 374 (1%) patients registered in the DCAR compared to 29,882 patients with OHCA from other causes. Drowning-related OHCA more frequently occurred at a public location (87% vs 25%, p < 0.001) and were more frequently witnessed by bystanders (80% vs 55%, p < 0.001). Both 30-day and 1-year survival for patients with drowning-related OHCA were significantly higher compared to OHCA from other causes (33% vs 14% and 32% vs 13%, respectively, p < 0.001). The adjusted odds ratio for 30-day survival for drowning-related OHCA and other causes of OHCA was 2.3 [1.7-3.2], p < 0.001. Increased 30-day survival was observed for drowning-related OHCA occurring at swimming pools compared to public location OHCA from other causes with an OR of 11.6 [6.0-22.6], p < 0.001. CONCLUSIONS: This study found higher 30-day survival among drowning-related OHCA compared to OHCA from other causes. This study proposed that a text-search algorithm (Danish Drowning Formula) could explore unstructured text fields to identify drowning persons. This method may present a low-resource solution to inform the drowning statistics in the future. REGISTRATION: This study was registered at ClinicalTrials.gov before analyses (NCT05323097).

Chronic airway disease in primary ciliary dyskinesia-spiced with geno-phenotype associations.

Primary ciliary dyskinesia (PCD) can be defined as a multiorgan ciliopathy with a dominant element of chronic airway disease affecting the nose, sinuses, middle ear, and in particular, the lower airways. Although most patients with PCD are diagnosed during preschool years, it is obvious that the chronic lung disease starts its course already from birth. The many faces of the clinical picture change, as does lung function, structural lung damage, the burden of infection, and of treatment throughout life. A markedly severe neutrophil inflammation in the respiratory tract seems pervasive and is only to a minimal extent ameliorated by a treatment strategy, which is predominantly aimed at bacterial infections. An ever-increasing understanding of the different aspects, their interrelationships, and possible different age courses conditioned by the underlying genotype is the focus of much attention. The future is likely to offer personalized medicine in the form of mRNA therapy, but to that end, it is of utmost importance that all patients with PCD be carefully characterized and given a genetic diagnosis. In this narrative review, we have concentrated on lower airways and summarized the current understanding of the chronic airway disease in this motile ciliopathy. In addition, we highlight the challenges, gaps, and opportunities in PCD lung disease research.

A retrospective review of Achromobacter species and antibiotic treatments in patients with primary ciliary dyskinesia.

Objectives: Primary ciliary dyskinesia (PCD) is a rare congenital disease with defective mucociliary clearance causing frequent and often persistent pulmonary infections. Achromobacter species are opportunistic pathogens renowned for the difficulty of effective treatments and deteriorating effects on lung function. We aimed to describe the occurrence, treatment, and rate of successful eradication of Achromobacter species in patients with PCD. Methods: We retrospectively reviewed 18 years of historical microbiological samples and 10 years of electronic health records for PCD patients in Denmark. Results: We included 136 patients. Twenty-six patients had isolates of Achromobacter species. On average, 5% of the cohort had at least one annual isolate. Infections became persistent in 38% with a median length of 6.6 years leading to a significant number of antibiotic treatments. Resistance toward tobramycin and ciprofloxacin was prevalent. Overall, successful eradication was achieved in 62% of patients. We found the course of lung function significantly worse during persistent Achromobacter species infection than during the two preceding years, but not different to the course in unaffected age-matched controls. Conclusion The prevalence of Achromobacter species in patients with PCD is in line with what has been reported in cystic fibrosis and can occur transiently, intermittently, or develop into a serious persistent lung infection associated with long-term antibiotic treatment.

Proof of Concept: Very Rapid Tidal Breathing Nasal Nitric Oxide Sampling Discriminates Primary Ciliary Dyskinesia from Healthy Subjects.

INTRODUCTION: Nasal nitric oxide (nNO) is extremely low in individuals with primary ciliary dyskinesia (PCD) and is recommended as part of early workup. We investigated whether tidal breathing sampling for a few seconds was as discriminative between PCD and healthy controls (HC) as conventional tidal breathing sampling (cTB-nNO) for 20-30 s. METHODS: We performed very rapid sampling of tidal breathing (vrTB-nNO) for 2, 4 and 6 s, respectively. Vacuum sampling with applied negative pressure (vrTB-nNOvac; negative pressure was applied by pinching the sampling tube) for < 2 s resulted in enhanced suction of nasal air during measurement. Feasibility, success rate, discriminatory capacity, repeatability and agreement were assessed for all four sampling modalities. RESULTS: We included 13 patients with PCD, median (IQR) age of 21.8 (12.2-27.7) years and 17 HC, 25.3 (14.5-33.4) years. Measurements were highly feasible (96.7% success rate). Measured NO values with vrTB-nNO modalities differed significantly from TB-nNO measurements (HC: p < 0.001, PCD: p < 0.05). All modalities showed excellent discrimination. The vacuum method gave remarkably high values of nNO in both groups (1865 vs. 86 ppb), but retained excellent discrimination. vrTB-nNO4sec, vrTB-nNO6sec and vrTB-nNOvac showed identical specificity to cTB-nNO (all: 1.0, 95% CI 0.77-1.0). CONCLUSION: vrTB-nNO sampling requires only a few seconds of probe-in-nose time, is feasible, and provides excellent discrimination between PCD and HC. Rapid TB-nNO sampling needs standardisation and further investigations in infants, young children and patients referred for PCD workup.

Pulmonary radioaerosol mucociliary clearance assessment: searching for genotype-specific differences and potential as an outcome measure in primary ciliary dyskinesia.

Background: Pulmonary radioaerosol mucociliary clearance (PRMC) is a reliable method for assessing in vivo whole lung mucociliary clearance and has been used at the Danish PCD Centre as a supplementary diagnostic test for primary ciliary dyskinesia (PCD) for more than two decades. This study aimed to investigate genotype-specific differences in PRMC measures and evaluate its potential as an outcome parameter. Material and methods: The study was based on a retrospective analysis of PRMC tests performed over a 24-year period (1999-2022) in individuals referred for PCD work-up and included patients with genetically confirmed PCD and non-PCD controls. Patients inhaled nebulised technetium-albumin-colloid before static and dynamic imaging was obtained. Three parameters were evaluated: 1-h lung retention (LR1), tracheobronchial velocity (TBV) and cough clearance. Results: The study included 69 patients from the Danish PCD cohort, representing 26 different PCD genotypes. Mucociliary clearance by PRMC was consistently absent in most PCD patients, regardless of genotype. However, a single patient with a CCDC103 mutation, preserved ciliary function and normal nasal nitric oxide levels exhibited normal LR1 and low TBV values. Voluntary cough significantly improved clearance, with a median improvement of 11% (interquartile range 4-24%). Conclusion: Absent mucociliary clearance by PRMC should be expected in PCD regardless of genotype but residual ciliary function could result in measurable PRMC. This indicates a potential for PRMC to detect improvements in ciliary function if this can be restored. Addressing involuntary cough and peripheral deposition of radioaerosol is important if PRMC is to be used as an outcome measure in future clinical PCD trials.

Fitness and lung function in children with primary ciliary dyskinesia and cystic fibrosis.

BACKGROUND: Peak oxygen uptake (VO2peak) is associated with morbidity and mortality in health and disease, and provides important information of global physical health not achieved from standard pulmonary function tests. Primary ciliary dyskinesia (PCD) and cystic fibrosis (CF) are genetically determined diseases involving different basic defects, but both showing impaired mucociliary clearance leading to chronic infections and pulmonary destruction early in life. PCD is generally considered a milder disease than CF and it is hypothesized that children with CF would have consistently lower VO2peak and pulmonary function than children with PCD. METHODS: We performed a prospective, observational single-center, clinical cohort study of VO2peak and pulmonary function in age and gender matched schoolchildren, at two occasions 12 months apart. RESULTS: VO2peak was persistently (at baseline and after 12 months) and significantly reduced in the 22 patients with PCD (z-score = -0.89 and -1.0) and 24 with CF (z-score = -0.94 and -1.1), included in the study. Abnormal VO2peak was detected in a larger proportion of children with PCD (≈30%) than CF (≈13%). Moreover, children with PCD exhibited persistently lower FEV1 (p < 0.0001 at first visit and p = 0.001 at second visit) while FEF25-75 and FVC differed only at baseline. Indeed, a retrospective analysis comparing lung function over the last year in our entire PCD and CF populations between 6 and 18 years of age, revealed lower values in patients with PCD (FEV1 z-score, p = 0.0004, FVC z-score p < 0.0001, FEF25-75 z-score p = 0.008). CONCLUSION: This is the first report indicating that cardiopulmonary fitness is equally and consistently reduced in both children with PCD and CF along with a consistent lower pulmonary function in PCD compared with CF. A certain reservation for possible selection bias and the small number of patients is necessary. However, increased focus on early diagnosis, evidence-based treatment regimens and close clinical monitoring in PCD are warranted.