Nasal nitric oxide (nNO) concentrations are low in patients with primary ciliary dyskinesia (PCD) providing a noninvasive screening test. We conducted a systematic review of the literature to examine ...the utility of nNO in screening for PCD, in particular 1) different respiratory manoeuvres during sampling (velum closure, tidal breathing, etc.), 2) accuracy in screening young/uncooperative children, 3) stationary versus portable analysers, and 4) nNO in "atypical" PCD. 96 papers were assessed according to modified PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria and 22 were included in this review. Meta-analysis of 11 studies comparing nNO during a velum closure breath hold gave a mean±SD nNO of 19.4±18.6 nL·min(-1) in PCD (n = 478) and 265.0±118.9 nL·min(-1) in healthy controls (n = 338). Weighted mean difference for PCD versus healthy controls was 231.1 nL·min(-1) (95% CI 193.3-268.9; n = 338) and 114.1 nL·min(-1) (95% CI 101.5-126.8; n = 415) for PCD versus cystic fibrosis. Five studies of nNO measurement during tidal breathing demonstrated that this is an acceptable manoeuvre in young children where velum closure is not possible, but the discriminatory value was reduced. Four small studies of portable NO analysers suggest these are reliable tools for screening for PCD. However, nNO must be interpreted alongside clinical suspicion. Future studies should focus on standardising sampling techniques and reporting.
Angiotensin-converting enzyme 2 (ACE2) is the main entry point in airway epithelial cells for SARS-CoV-2. ACE2 binding to the SARS-CoV-2 protein spike triggers viral fusion with the cell plasma ...membrane, resulting in viral RNA genome delivery into the host. Despite ACE2's critical role in SARS-CoV-2 infection, full understanding of ACE2 expression, including in response to viral infection, remains unclear. ACE2 was thought to encode five transcripts and one protein of 805 amino acids. In the present study, we identify a novel short isoform of ACE2 expressed in the airway epithelium, the main site of SARS-CoV-2 infection. Short ACE2 is substantially upregulated in response to interferon stimulation and rhinovirus infection, but not SARS-CoV-2 infection. This short isoform lacks SARS-CoV-2 spike high-affinity binding sites and, altogether, our data are consistent with a model where short ACE2 is unlikely to directly contribute to host susceptibility to SARS-CoV-2 infection.
Few original studies have described the prevalence and severity of clinical symptoms of primary ciliary dyskinesia (PCD). This systematic review and meta-analysis aimed to identify all published ...studies on clinical manifestations of PCD patients, and to describe their prevalence and severity stratified by age and sex.We searched PubMed, Embase and Scopus for studies describing clinical symptoms of ≥10 patients with PCD. We performed meta-analyses and meta-regression to explain heterogeneity.We included 52 studies describing a total of 1970 patients (range 10-168 per study). We found a prevalence of 5% for congenital heart disease. For the rest of reported characteristics, we found considerable heterogeneity (I
range 68-93.8%) when calculating the weighted mean prevalence. Even after taking into account the explanatory factors, the largest part of the between-studies variance in symptom prevalence remained unexplained for all symptoms. Sensitivity analysis including only studies with test-proven diagnosis showed similar results in prevalence and heterogeneity.Large differences in study design, selection of study populations and definition of symptoms could explain the heterogeneity in symptom prevalence. To better characterise the disease, we need larger, multicentre, multidisciplinary, prospective studies that include all age groups, use uniform diagnostics and report on all symptoms.
Primary ciliary dyskinesia (PCD) is a rare genetic disease that affects the motility of cilia, leading to impaired mucociliary clearance. It is estimated that the vast majority of patients with PCD ...have not been diagnosed as such, providing a major obstacle to delivering appropriate care. Challenges in diagnosing PCD include lack of disease-specific symptoms and absence of a single, "gold standard", diagnostic test. Management of patients is currently not based on high-level evidence because research findings are mostly derived from small observational studies with limited follow-up period. In this review, we provide a critical overview of the available literature on clinical care for PCD patients, including recent advances. We identify barriers to PCD research and make suggestions for overcoming challenges.
Symptoms of primary ciliary dyskinesia (PCD) are nonspecific and guidance on whom to refer for testing is limited. Diagnostic tests for PCD are highly specialised, requiring expensive equipment and ...experienced PCD scientists. This study aims to develop a practical clinical diagnostic tool to identify patients requiring testing.Patients consecutively referred for testing were studied. Information readily obtained from patient history was correlated with diagnostic outcome. Using logistic regression, the predictive performance of the best model was tested by receiver operating characteristic curve analyses. The model was simplified into a practical tool (PICADAR) and externally validated in a second diagnostic centre.Of 641 referrals with a definitive diagnostic outcome, 75 (12%) were positive. PICADAR applies to patients with persistent wet cough and has seven predictive parameters: full-term gestation, neonatal chest symptoms, neonatal intensive care admittance, chronic rhinitis, ear symptoms, situs inversus and congenital cardiac defect. Sensitivity and specificity of the tool were 0.90 and 0.75 for a cut-off score of 5 points. Area under the curve for the internally and externally validated tool was 0.91 and 0.87, respectively.PICADAR represents a simple diagnostic clinical prediction rule with good accuracy and validity, ready for testing in respiratory centres referring to PCD centres.
Abstract
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.
Graphical abstract
Primary ciliary dyskinesia has a variable impact on fertility in men and women.
Dynein-decorated doublet microtubules (DMTs) are critical components of the oscillatory molecular machine of cilia, the axoneme, and have luminal surfaces patterned periodically by microtubule inner ...proteins (MIPs). Here we present an atomic model of the 48-nm repeat of a mammalian DMT, derived from a cryoelectron microscopy (cryo-EM) map of the complex isolated from bovine respiratory cilia. The structure uncovers principles of doublet microtubule organization and features specific to vertebrate cilia, including previously unknown MIPs, a luminal bundle of tektin filaments, and a pentameric dynein-docking complex. We identify a mechanism for bridging 48- to 24-nm periodicity across the microtubule wall and show that loss of the proteins involved causes defective ciliary motility and laterality abnormalities in zebrafish and mice. Our structure identifies candidate genes for diagnosis of ciliopathies and provides a framework to understand their functions in driving ciliary motility.
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•Structure of the 48-nm repeat of a mammalian doublet microtubule from respiratory cilia•Tektin filaments bind within the lumens of doublet microtubules•A pentameric docking complex attaches axonemal dyneins to doublet microtubules•Loss of connectivity across microtubule walls causes ciliopathy-like phenotypes
Characterizing the structural organization of mammalian ciliary microtubules provides a context for understanding cilium dynamics and the potential effect of mutations associated with human ciliopathies.
Diagnosis of primary ciliary dyskinesia (PCD) relies on a combination of tests. High-speed video microscopy analysis (HSVA) is widely used to contribute to the diagnosis. It can be analyzed on the ...day of diagnostic consultation, but the qualitative analyses are subjective. Diagnostic accuracy and reliability of assessing ciliary function have not been robustly evaluated. We aimed to establish the accuracy of HSVA to diagnose PCD compared with a combination of tests, and to assess the interobserver reliability of HSVA analysis.
We randomly selected and anonymized archived videos from 120 patients seen at three UK PCD centers. Three experienced scientists independently reviewed six videos per patient, using a standardized proforma, blinded to diagnostic and clinical data. We compared study outcomes with two references: (1) a combination of diagnostic tests in accordance with the European Respiratory Society PCD diagnostic guidelines and (2) original clinical outcome determined by all available diagnostic tests.
HSVA had excellent sensitivity and specificity to diagnose PCD: (1) 100% and 96%, respectively, compared with ERS guidelines, and (2) 96% and 91% compared with diagnostic outcomes. There was high interobserver agreement for “PCD-positive” outcomes (κ = 0.7).
Specialist scientists accurately diagnosed PCD using HSVA, with high interobserver agreement. HSVA can be reliably used to counsel patients and commence treatment on the day of testing while awaiting confirmatory investigations.
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