Validation of a portable nitric oxide analyzer for screening in primary ciliary dyskinesias

The assessment of exhaled nitric oxide in patients with obesity and asthma before and after exercise

OBJECTIVE

It is well-known that children who suffer from obesity and asthma may also have exercise-induced bronchospasm. Exhaled nitric oxide is an indicator of airway inflammation, and could be affected by exercise. This study looked at how exercise, which is a typical cause of acute airway obstruction, affects the levels of FeNO and spirometric parameters in obese and asthmatic children.

MATERIALS AND METHODS

Seventy children between the ages of 6 and 18 were divided into four groups: healthy children, obese children with asthma, obese children without asthma, and normal-weight asthmatic children. FeNO and spirometric parameters were assessed before and after exercise. Their heart rate was raised to 160-170 beats per minute by walking on a flat surface.

RESULTS

The highest mean FeNO was seen in the asthmatic-obese group, while the lowest mean FeNO was found in the healthy group. MEF25-75 increased with exercise in the obese non-asthmatic group. FEV1/FVC was the lowest in the asthmatic-obese group.

CONCLUSIONS

FeNO and FEV1/FVC have a strong association with asthma. The highest values of FeNO found in asthma-obesity combined. It was seen that obesity increased inflammation but exercise did not affect FeNO values. FeNO and FEV1 values were found to be higher in obese patients with and without asthma than normal weight and overweight asthmatics and non-asthmatics.

Nasal Nitric Oxide in Children: A Review of Current Outreach in Pediatric Respiratory Medicine

Nasal nitric oxide (nNO) is a gas synthesized by the inducible and constitutive NO synthase (NOS) enzyme in the airway cells of the nasal mucosa. Like lung nitric oxide, it is thought to be associated with airway inflammation in various respiratory diseases in children. The aim of our review was to investigate the current state of use of nNO measurement in children. A comprehensive search was conducted using the Web of Science and PubMed databases specifically targeting publications in the English language, with the following keywords: nasal NO, children, allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, primary ciliary dyskinesia (PCD), and cystic fibrosis (CF). We describe the use of nNO in pediatric allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, PCD, and CF based on the latest literature. nNO is a noninvasive, clinically applicable test for use in pediatric allergic rhinitis, chronic rhinosinusitis, acute rhinosinusitis, PCD, and CF. It can be used as a complementary method in the diagnosis of these respiratory diseases and as a monitoring method for the treatment of allergic rhinitis and acute and chronic rhinosinusitis.

Nasal Nitric Oxide as a Biomarker in the Diagnosis and Treatment of Sinonasal Inflammatory Diseases: A Review of the Literature

OBJECTIVE

To critically review the literature on nasal nitric oxide (nNO) and its current clinical and research applicability in the diagnosis and treatment of different sinonasal inflammatory diseases, including acute bacterial rhinosinusitis (ABRS), allergic rhinitis (AR), and chronic rhinosinusitis (CRS).

METHODS

A search of the PubMed database was conducted to include articles on nNO and sinonasal diseases from January 2003 to January 2020. All article titles and abstracts were reviewed to assess their relevance to nNO and ABRS, AR, or CRS. After selection of the manuscripts, full-text reviews were performed to synthesize current understandings of nNO and its applications to the various sinonasal inflammatory diseases.

RESULTS

A total of 79 relevant studies from an initial 559 articles were identified using our focused search and review criteria. nNO has been consistently shown to be decreased in ABRS and CRS, especially in cases with nasal polyps. While AR is associated with elevations in nNO, nNO levels have also been found to be lower in AR cases with higher symptom severity. The obstruction of the paranasal sinuses is speculated to be an important variable in the relationship between nNO and the sinonasal diseases. Treatment of these diseases appears to affect nNO through the reduction of inflammatory disease burden and also mitigation of sinus obstruction.

CONCLUSION

nNO has been of increasing interest to researchers and clinicians over the last decade. The most compelling data for nNO as a clinical tool involve CRS. nNO can be used as a marker of ostiomeatal complex patency. Variations in measurement techniques and technology continue to impede standardized interpretation and implementation of nNO as a biomarker for sinonasal inflammatory diseases.

Nasal nitric oxide measurement variability to establish a standard for reliable results

Nasal nitric oxide (nNO) measurement is a first-line test used to increase the post-measurement probability of primary ciliary dyskinesia (PCD) in subjects with symptoms consistent with this diagnosis [1]. The accuracy of nNO measurement is essential since it will orientate the work-up towards tests that are usually highly specialised and sometimes invasive. Accuracy of biological measurements relies on the technical and on the biological variability. While the accuracy of NO analysers is known better for chemiluminescence devices (e.g. <1 ppb with 1% linearity from 0.1 to 5000 ppb for CLD 88 (Eco Medics, Duernten, Switzerland)) than for widely used electrochemical devices (e.g. ±5 ppb for values <50 ppb and 10% for values >50 ppb for Niox Vero (Circassia, Oxford, UK)) [2], little is known on the biological variability of nNO measurements, except for increased nNO output variability in adults with rhinitis compared with healthy subjects and the positive effect of training on the level of nNO taken during expiration against a resistance (nNO-ER) in children [3, 4].

A repeatability of 10% for NO measurements obtained with the velum closed in the same or both nostrils is relevant, while measurements taken during tidal breathing should aim for a repeatability of 20% and 30%, respectivelyhttps://bit.ly/3sMnug6

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

Nasal nitric oxide (nNO) measurements are routinely used in the assessment of patients suspected to have 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 measurements in children, an international online survey was conducted to better understand current practices for measuring nNO among providers involved in PCD diagnostics.

Seventy-eight professionals responded, representing 65 centres across 18 countries, mainly located in Europe and North America. Nearly all centres measured nNO in children and more than half of them 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 (49/65) or during tidal breathing (50/65) with 15 centres using only exhalation against a resistance and 15 centres using only tidal breathing. The cut-off values used to discriminate PCD was consistent across centres using chemiluminescence analyzers and these centres reported results as an output (nL.min−1). However, cut-off values were highly variable across centres using electrochemical devices, and nNO concentrations were typically reported as ppb.

This survey represents the first to determine real-world use of nNO measurements worldwide and revealed remarkable variability in methodology, equipment, and interpretation. These findings will be useful to standardise methods and training.

Feasibility of nasal NO screening in healthy newborns

BACKGROUND

Nasal nitric oxide (nNO) measurement is recommended as a first line screening test for primary ciliary dyskinesia (PCD). While reliable velum- and non-velum-closure techniques exist for preschool children and older individuals, no data are available for neonates.

AIMS

To determine feasibility of nNO screening and nNO concentration in healthy newborns in the first week of life.

METHODS

Nasal NO was analyzed in tidal breathing during natural sleep using a CLD-88 sp NO analyzer (chemoluminescence sensor) and a NIOX MINO (electrochemical sensor). Test success and nNO concentration were determined and compared between the two devices.

RESULTS

Nasal NO was measured in 62 healthy neonates within the first week of life. Feasibility of nNO measurement was 100% for at least one nostril and 85.5% for both nostrils using the chemoluminescence device, but significantly lower with the electrochemical device (85.5% and 53.2%; p < .001). Median nNO concentration was 38 ppb (interquartile range, 27-55; range, 9-100) with the ECOMEDICS device and 23 (15-33, 8-59) with the NIOX MINO (p < .001), with a trend towards higher values for older subjects. None of the subjects exceeded nNO levels of 100 ppb.

CONCLUSION

Measurement of nNO using a chemoluminescence device is highly feasible in newborns during natural sleep. However, nNO levels are considerably lower compared to the published data for older individuals and in the range of a PCD reference group of infants between 4 and 8 weeks of age, potentially resulting in a great overlap with subjects with PCD in this age group. Therefore, screening for PCD using nasal NO might not be useful in the first week of life. Upon clinical suspicion, other diagnostic tests such as high-speed video analysis of the cilia should be applied.

Progress in Diagnosing Primary Ciliary Dyskinesia: The North American Perspective

Primary Ciliary Dyskinesia (PCD) is a rare, under-recognized disease that affects respiratory ciliary function, resulting in chronic oto-sino-pulmonary disease. The PCD clinical phenotype overlaps with other common respiratory conditions and no single diagnostic test detects all forms of PCD. In 2018, PCD experts collaborated with the American Thoracic Society (ATS) to create a clinical diagnostic guideline for patients across North America, specifically considering the local resources and limitations for PCD diagnosis in the United States and Canada. Nasal nitric oxide (nNO) testing is recommended for first-line testing in patients ≥5 years old with a compatible clinical phenotype; however, all low nNO values require confirmation with genetic testing or ciliary electron micrograph (EM) analysis. Furthermore, these guidelines recognize that not all North American patients have access to nNO testing and isolated genetic testing is appropriate in cases with strong clinical PCD phenotypes. For unresolved diagnostic cases, referral to a PCD Foundation accredited center is recommended. The purpose of this narrative review is to provide insight on the North American PCD diagnostic process, to enhance the understanding of and adherence to current guidelines, and to promote collaboration with diagnostic pathways used outside of North America.

Nasal Nitric Oxide Measurement in Primary Ciliary Dyskinesia. A Technical Paper on Standardized Testing Protocols

Nasal nitric oxide concentrations are extremely low in primary ciliary dyskinesia (PCD), and measurement of this nasal gas is recommended as a PCD diagnostic test in cooperative patients aged 5 years and older. However, nasal nitric oxide measurements must be performed with chemiluminescence analyzers using a standardized protocol to ensure proper results, because nasal nitric oxide values can be influenced by various internal and external factors. Repeat nasal nitric oxide testing on separate visits is required to ensure that low diagnostic values are persistent and consistent with PCD. This technical paper presents the standard operating procedures for nasal nitric oxide measurement used by the PCD Foundation Clinical and Research Centers Network at various specialty centers across North America. Adherence to this document ensures reliable nasal nitric oxide testing and high diagnostic accuracy when employed in a population with appropriate clinical phenotypes for PCD.

Primary ciliary dyskinesia: a major player in a bigger game

Primary ciliary dyskinesia (PCD) is an inherited disorder of clinical and genetic heterogeneity resulting from mutations in genes involved in the transport, assembly and function of motile cilia. The resulting impairment in mucociliary clearance means patients suffer from chronic progressive lung disease, bronchiectasis, rhinosinusitis and middle ear disease. Subfertility is common to both male and female patients. Situs abnormalities occur in around half of patients, with a subgroup suffering more complex situs arrangements where congenital heart defects or other organ abnormalities frequently coexist. Variations from the classical PCD phenotype are increasingly recognised where overlapping features across a range of motile and nonmotile ciliopathies are redefining our approach to both diagnosis and management of these complex conditions. PCD offers an ideal opportunity for direct visualisation of ciliary function and structure, following nasal brush biopsy, allowing opportunities for researchers to directly interrogate the downstream impact of loss of function mutations. In turn, this has led to rapid advances in the development of new diagnostic tests. These advances mean that PCD is an excellent disease model for understanding the genetic and mechanistic causes of the clinical phenotype for all respiratory ciliopathies. Furthermore, the overlapping role of motile ciliary defects in a wider set of complex and syndromic disorders related to loss of function mutations in primary, nonmotile cilia has been recognised. As we better understand the role of ciliary defects in a broad spectrum of diseases, we should aim to map out a framework through which we can identify, diagnose and treat all respiratory ciliopathies.

Key points

Primary ciliary dyskinesia is just one of a group of conditions where a heterogeneous array of genetic mutations affect the assembly or structure of motile cilia.Overlapping phenotypes between motile and nonmotile ciliopathies are redefining the diagnostic and therapeutic approach to encompass all ciliopathy patients with a respiratory phenotype.An extended diagnostic algorithm may be required to capture the majority of cases with a respiratory ciliopathy, including patients with syndromic ciliopathies.The terminology around disorders of motile cilia is becoming more descriptive to better reflect the heterogeneity and underlying disease mechanisms across the spectrum of respiratory ciliopathies.

Educational aims

To summarise the existing knowledge base around the disease mechanisms for respiratory ciliopathies, including primary ciliary dyskinesia (PCD).To explore and understand the reasons for changing terminology around respiratory ciliopathies.To emphasise key messages around the diagnosis and treatment of all ciliopathies.Diagnosing PCD is complex and time consuming, and there is no single stand-alone test that can confirm or exclude a diagnosis in all cases.

Motile ciliopathies

Motile cilia are highly complex hair-like organelles of epithelial cells lining the surface of various organ systems. Genetic mutations (usually with autosomal recessive inheritance) that impair ciliary beating cause a variety of motile ciliopathies, a heterogeneous group of rare disorders. The pathogenetic mechanisms, clinical symptoms and severity of the disease depend on the specific affected genes and the tissues in which they are expressed. Defects in the ependymal cilia can result in hydrocephalus, defects in the cilia in the fallopian tubes or in sperm flagella can cause female and male subfertility, respectively, and malfunctional motile monocilia of the left-right organizer during early embryonic development can lead to laterality defects such as situs inversus and heterotaxy. If mucociliary clearance in the respiratory epithelium is severely impaired, the disorder is referred to as primary ciliary dyskinesia, the most common motile ciliopathy. No single test can confirm a diagnosis of motile ciliopathy, which is based on a combination of tests including nasal nitric oxide measurement, transmission electron microscopy, immunofluorescence and genetic analyses, and high-speed video microscopy. With the exception of azithromycin, there is no evidence-based treatment for primary ciliary dyskinesia; therapies aim at relieving symptoms and reducing the effects of reduced ciliary motility.

Registries and collaborative studies for primary ciliary dyskinesia in Europe

Primary ciliary dyskinesia (PCD) is a rare inherited disease characterised by malfunctioning cilia leading to a heterogeneous clinical phenotype with many organ systems affected. There is a lack of data on clinical presentation, prognosis and effectiveness of treatments, making it mandatory to improve the scientific evidence base.

This article reviews the data resources that are available in Europe for clinical and epidemiological research in PCD, namely established national PCD registries and national cohort studies, plus two large collaborative efforts (the international PCD (iPCD) Cohort and the International PCD Registry), and discusses their strengths, limitations and perspectives.

Denmark, Cyprus, Norway and Switzerland have national population-based registries, while England and France conduct multicentre cohort studies. Based on the data contained in these registries, the prevalence of diagnosed PCD is 3–7 per 100 000 in children and 0.2–6 per 100 000 in adults. All registries, together with other studies from Europe and beyond, contribute to the iPCD Cohort, a collaborative study including data from over 4000 PCD patients, and to the International PCD Registry, which is part of the ERN (European Reference Network)-LUNG network.

This rich resource of readily available, standardised and contemporaneous data will allow obtaining fast answers to emerging clinical and research questions in PCD.

The growing collaborative network of national and international registries and cohort studies of patients with PCD provides an excellent resource for research on this rare diseasehttps://bit.ly/3dto75l

Nitric Oxide and Biological Mediators in Pediatric Chronic Rhinosinusitis and Asthma

BACKGROUND

In the context of the so-called unified airway theory, chronic rhinosinusitis (CRS) and asthma may coexist. The inflammation underlying these conditions can be studied through the aid of biomarkers. Main body: We described the main biological mediators that have been studied in pediatric CRS and asthma, and, according to the available literature, we reported their potential role in the diagnosis and management of these conditions. As for CRS, we discussed the studies that investigated nasal nitric oxide (nNO), pendrin, and periostin. As for asthma, we discussed the role of fractional exhaled nitric oxide (feNO), the role of periostin, and that of biological mediators measured in exhaled breath condensate (EBC) and exhaled air (volatile organic compounds, VOCs).

CONCLUSION

Among non-invasive biomarkers, nNO seems the most informative in CRS and feNO in asthma. Other biological mediators seem promising, but further studies are needed before they can be applied in clinical practice.

Primary ciliary dyskinesia in the genomics age

Primary ciliary dyskinesia is a genetically and clinically heterogeneous syndrome. Impaired function of motile cilia causes failure of mucociliary clearance. Patients typically present with neonatal respiratory distress of unknown cause and then continue to have a daily wet cough, recurrent chest infections, perennial rhinosinusitis, otitis media with effusion, and bronchiectasis. Approximately 50% of patients have situs inversus, and infertility is common. While understanding of the underlying genetics and disease mechanisms have substantially advanced in recent years, there remains a paucity of evidence for treatment. Next-generation sequencing has increased gene discovery, and mutations in more than 40 genes have been reported to cause primary ciliary dyskinesia, with many other genes likely to be discovered. Increased knowledge of cilia genes is challenging perceptions of the clinical phenotype, as some genes reported in the last 5 years are associated with mild respiratory disease. Developments in genomics and molecular medicine are rapidly improving diagnosis, and a genetic cause can be identified in approximately 70% of patients known to have primary ciliary dyskinesia. Groups are now investigating novel and personalised treatments, although gene therapies are unlikely to be available in the near future.

Diagnosis of Primary Ciliary Dyskinesia. An Official American Thoracic Society Clinical Practice Guideline

BACKGROUND

This document presents the American Thoracic Society clinical practice guidelines for the diagnosis of primary ciliary dyskinesia (PCD).

TARGET AUDIENCE

Clinicians investigating adult and pediatric patients for possible PCD.

METHODS

Systematic reviews and, when appropriate, meta-analyses were conducted to summarize all available evidence pertinent to our clinical questions. Evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach for diagnosis and discussed by a multidisciplinary panel with expertise in PCD. Predetermined conflict-of-interest management strategies were applied, and recommendations were formulated, written, and graded exclusively by the nonconflicted panelists. Three conflicted individuals were also prohibited from writing, editing, or providing feedback on the relevant sections of the manuscript.

RESULTS

After considering diagnostic test accuracy, confidence in the estimates for each diagnostic test, relative importance of test results studied, desirable and undesirable direct consequences of each diagnostic test, downstream consequences of each diagnostic test result, patient values and preferences, costs, feasibility, acceptability, and implications for health equity, the panel made recommendations for or against the use of specific diagnostic tests as compared with using the current reference standard (transmission electron microscopy and/or genetic testing) for the diagnosis of PCD.

CONCLUSIONS

The panel formulated and provided a rationale for the direction as well as for the strength of each recommendation to establish the diagnosis of PCD.

Severe pulmonary disease in an adult primary ciliary dyskinesia population in Brazil

Primary Ciliary Dyskinesia (PCD) is underdiagnosed in Brazil. We enrolled patients from an adult service of Bronchiectasis over a two-year period in a cross-sectional study. The inclusion criteria were laterality disorders (LD), cough with recurrent infections and the exclusion of other causes of bronchiectasis. Patients underwent at least two of the following tests: nasal nitric oxide, ciliary movement and analysis of ciliary immunofluorescence, and genetic tests (31 PCD genes + CFTR gene). The clinical characterization included the PICADAR and bronchiectasis scores, pulmonary function, chronic Pseudomonas aeruginosa (cPA) colonization, exhaled breath condensate (EBC) and mucus rheology (MR). Forty-nine of the 500 patients were diagnosed with definite (42/49), probable (5/49), and clinical (2/49) PCD. Twenty-four patients (24/47) presented bi-allelic pathogenic variants in a total of 31 screened PCD genes. A PICADAR score > 5 was found in 37/49 patients, consanguinity in 27/49, LD in 28/49, and eight PCD sibling groups. FACED diagnosed 23/49 patients with moderate or severe bronchiectasis; FEV1 ≤ 50% in 25/49 patients, eight patients had undergone lung transplantation, four had been lobectomized and cPA+ was determined in 20/49. The EBC and MR were altered in all patients. This adult PCD population was characterized by consanguinity, severe lung impairment, genetic variability, altered EBC and MR.

Cost-effectiveness analysis of three algorithms for diagnosing primary ciliary dyskinesia: a simulation study

Background

Primary Ciliary Dyskinesia (PCD) diagnosis relies on a combination of tests which may include (a) nasal Nitric Oxide (nNO), (b) High Speed Video Microscopy (HSVM) and (c) Transmission Electron Microscopy (TEM). There is variability in the availability of these tests and lack of universal agreement whether diagnostic tests should be performed in sequence or in parallel. We assessed three combinations of tests for PCD diagnosis and estimated net sensitivity and specificity as well as cost-effectiveness (CE) and incremental cost-effectiveness (ICE) ratios.

Methods and results

A hypothetical initial population of 1000 referrals (expected 320 PCD patients) was followed through a probabilistic decision analysis model which was created to assess the CE of three diagnostic algorithms (a) nNO + TEM in sequence, (b) nNO + HSVM in sequence and (c) nNO/HSVM in parallel followed, in cases with conflicting results, by confirmatory TEM (nNO/HSVM+TEM). Number of PCD patients identified, CE and ICE ratios were calculated using Monte Carlo simulations. Out of 320 expected PCD patients, 313 were identified by nNO/HSVM+TEM, 274 with nNO + HSVM and 198 with nNO + TEM. The nNO/HSVM+TEM had the highest mean annual cost (€209 K) followed by nNO + TEM (€150 K) and nNO + HSVM (€136 K). The nNO + HSVM algorithm dominated the nNO + TEM algorithm (less costly and more effective). The ICE ratio for nNO/HSVM+TEM was €2.1 K per additional PCD patient identified.

Conclusions

The diagnostic algorithm (nNO/HSVM+TEM) with parallel testing outperforms algorithms with tests in sequence. These findings, can inform the dialogue on the development of evidence-based guidelines for PCD diagnostic testing. Future research in understudied aspects of the disease, such as PCD-related quality of life and PCD-associated costs, is needed to help the better implementation of these guidelines across various healthcare systems.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1116-3) contains supplementary material, which is available to authorized users.

Accuracy of Nasal Nitric Oxide Measurement as a Diagnostic Test for Primary Ciliary Dyskinesia. A Systematic Review and Meta-analysis

RATIONALE

Primary ciliary dyskinesia (PCD) is a rare disorder causing chronic otosinopulmonary disease, generally diagnosed through evaluation of respiratory ciliary ultrastructure and/or genetic testing. Nasal nitric oxide (nNO) measurement is used as a PCD screening test because patients with PCD have low nNO levels, but its value as a diagnostic test remains unknown.

OBJECTIVES

To perform a systematic review to assess the utility of nNO measurement (index test) as a diagnostic tool compared with the reference standard of electron microscopy (EM) evaluation of ciliary defects and/or detection of biallelic mutations in PCD genes.

DATA SOURCES

Ten databases were searched for reference sources from database inception through July 29, 2016.

DATA EXTRACTION

Study inclusion was limited to publications with rigorous nNO index testing, reference standard diagnostic testing with EM and/or genetics, and calculable diagnostic accuracy information for cooperative patients (generally >5 yr old) with high suspicion of PCD.

SYNTHESIS

Meta-analysis provided a summary estimate for sensitivity and specificity and a hierarchical summary receiver operating characteristic curve. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to assess study quality, and Grading of Recommendations Assessment, Development, and Evaluation was used to assess the certainty of evidence. In 12 study populations (1,344 patients comprising 514 with PCD and 830 without PCD), using a reference standard of EM alone or EM and/or genetic testing, summary sensitivity was 97.6% (92.7-99.2) and specificity was 96.0% (87.9-98.7), with a positive likelihood ratio of 24.3 (7.6-76.9), a negative likelihood ratio of 0.03 (0.01-0.08), and a diagnostic odds ratio of 956.8 (141.2-6481.5) for nNO measurements. After studies using EM alone as the reference standard were excluded, the seven studies using an extended reference standard of EM and/or genetic testing showed a summary sensitivity of nNO measurements of 96.3% (88.7-98.9) and specificity of 96.4% (85.1-99.2), with a positive likelihood ratio of 26.5 (5.9-119.1), a negative likelihood ratio of 0.04 (0.01-0.12), and a diagnostic odds ratio of 699.3 (67.4-7256.0). Certainty of the evidence was graded as moderate.

CONCLUSIONS

nNO is a sensitive and specific test for PCD in cooperative patients (generally >5 yr old) with high clinical suspicion for this disease. With a moderate level of evidence, this meta-analysis confirms that nNO testing using velum closure maneuvers has diagnostic accuracy similar to EM and/or genetic testing for PCD when cystic fibrosis is ruled out. Thus, low nNO values accompanied by an appropriate clinical phenotype could be used as a diagnostic PCD test, though EM and/or genetics will continue to provide confirmatory information.

How to use nasal nitric oxide in a child with suspected primary ciliary dyskinesia

Measuring nasal nitric oxide (nNO) is increasingly used as part of testing for primary ciliary dyskinesia (PCD). The diagnosis of PCD is often delayed until after bronchiectasis is established and auditory damage has occurred. It is important that all paediatricians are aware of clinical features that are suggestive of PCD that should prompt diagnostic testing. nNO levels are recognised to be low in people with PCD and results generated by static chemiluminescence analysers using velum closure technique in older children have good sensitivity and specificity. However, to conclusively rule PCD in or out, further tests of ciliary function are required and assessment of cilia ultrastructure, immunohistochemistry studies and genotyping may also be indicated. These tests are more complex, invasive and expensive than nNO. nNO is less well studied in younger children where tidal breathing measurements are required. Portable nitric oxide analysers are also increasingly used in practice. This paper discusses when to consider PCD as a possible diagnosis in a child along with the indications, physiological and technical background and clinical utility of nNO as a test for PCD in children.

Normal values of offline exhaled and nasal nitric oxide in healthy children and teens using chemiluminescence

Nitric oxide (NO) can be used to detect respiratory or ciliary diseases. Fractional exhaled nitric oxide (FeNO) measurement can reflect ongoing eosinophilic airway inflammation and has a diagnostic utility as a test for asthma screening and follow-up while nasal nitric oxide (nNO) is a valuable screening tool for the diagnosis of primary ciliary dyskinesia. The possibility of collecting airway gas samples in an offline manner offers the advantage to extend these measures and improve the screening and management of these diseases, but normal values from healthy children and teens remain sparse.

METHODS

Samples were consecutively collected using the offline method for eNO and nNO chemiluminescence measurement in 88 and 31 healthy children and teens, respectively. Offline eNO measurement was also performed in 30 consecutive children with naïve asthma and/or respiratory allergy.

RESULTS

The normal offline eNO value was determined by the following regression equation -8.206 + 0.176 × height. The upper limit of the norm for the offline eNO value was 27.4 parts per billion (ppb). A separate analysis was performed in children, pre-teens and teens, for which offline eNO was 13.6 ± 4.7 ppb, 16.3 ± 13.7 ppb and 20.0 ± 7.2 ppb, respectively. The optimal cut-off value of the offline eNO to predict asthma or respiratory allergies was 23.3 ppb, with a sensitivity and specificity of 77% and 91%, respectively. Mean offline nNO was determined at 660 ppb with the lower limit of the norm at 197 ppb.

CONCLUSION

The use of offline eNO and nNO normal values should favour the widespread screening of respiratory diseases in children of school age in their usual environment.

Diagnosis of primary ciliary dyskinesia: potential options for resource-limited countries

Primary ciliary dyskinesia is a genetic disease of ciliary function leading to chronic upper and lower respiratory tract symptoms. The diagnosis is frequently overlooked because the symptoms are nonspecific and the knowledge about the disease in the primary care setting is poor. Additionally, none of the available tests is accurate enough to be used in isolation. These tests are expensive, and need sophisticated equipment and expertise to analyse and interpret results; diagnosis is therefore only available at highly specialised centres. The diagnosis is particularly challenging in countries with limited resources due to the lack of such costly equipment and expertise.

In this review, we discuss the importance of early and accurate diagnosis especially for countries where the disease is clinically prevalent but diagnostic tests are lacking. We review the diagnostic tests available in specialised centres (nasal nitric oxide, high-speed video microscopy, transmission electron microscopy, immunofluorescence and genetics). We then consider modifications that might be considered in less well-resourced countries whilst maintaining acceptable accuracy.

European Respiratory Society guidelines for the diagnosis of primary ciliary dyskinesia

The diagnosis of primary ciliary dyskinesia is often confirmed with standard, albeit complex and expensive, tests. In many cases, however, the diagnosis remains difficult despite the array of sophisticated diagnostic tests. There is no "gold standard" reference test. Hence, a Task Force supported by the European Respiratory Society has developed this guideline to provide evidence-based recommendations on diagnostic testing, especially in light of new developments in such tests, and the need for robust diagnoses of patients who might enter randomised controlled trials of treatments. The guideline is based on pre-defined questions relevant for clinical care, a systematic review of the literature, and assessment of the evidence using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach. It focuses on clinical presentation, nasal nitric oxide, analysis of ciliary beat frequency and pattern by high-speed video-microscopy analysis, transmission electron microscopy, genotyping and immunofluorescence. It then used a modified Delphi survey to develop an algorithm for the use of diagnostic tests to definitively confirm and exclude the diagnosis of primary ciliary dyskinesia; and to provide advice when the diagnosis was not conclusive. Finally, this guideline proposes a set of quality criteria for future research on the validity of diagnostic methods for primary ciliary dyskinesia.

Diagnostic Methods in Primary Ciliary Dyskinesia

Diagnosing primary ciliary dyskinesia is difficult. With no reference standard, a combination of tests is needed; most tests require expensive equipment and specialist scientists. We review the advances in diagnostic testing over the past hundred years, with emphasis on recent advances. We particularly focus on use of high-speed video analysis, transmission electron microscopy, nasal nitric oxide and genetic testing. We discuss the international efforts that are in place to advance the evidence base for diagnostic tests.

Diagnosis, monitoring, and treatment of primary ciliary dyskinesia: PCD foundation consensus recommendations based on state of the art review

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, rare lung disease resulting in chronic oto-sino-pulmonary disease in both children and adults. Many physicians incorrectly diagnose PCD or eliminate PCD from their differential diagnosis due to inexperience with diagnostic testing methods. Thus far, all therapies used for PCD are unproven through large clinical trials. This review article outlines consensus recommendations from PCD physicians in North America who have been engaged in a PCD centered research consortium for the last 10 years. These recommendations have been adopted by the governing board of the PCD Foundation to provide guidance for PCD clinical centers for diagnostic testing, monitoring, and appropriate short and long-term therapeutics in PCD patients.

Diagnostic accuracy of nasal nitric oxide for establishing diagnosis of primary ciliary dyskinesia: a meta-analysis

BACKGROUND

To date, diagnosis of Primary Ciliary Dyskinesia (PCD) remains difficult and challenging. We systematically evaluated the diagnostic performance of nasal Nitric Oxide (nNO) measurement for the detection of PCD, using either velum-closure (VC) or non-velum-closure (non-VC) techniques.

METHODS

All major electronic databases were searched from inception until March 2015 using appropriate terms. The sensitivity and specificity of nNO measurement was calculated in PCD patients diagnosed by transmission electron microscopy, high speed video-microscopy or genetic testing. Summary receiver operating characteristic (HSROC) curves were drawn using the parameters of the fitted models.

RESULTS

Twelve studies provided data for 13 different populations, including nine case-control (n = 793) and four prospective cohorts (n = 392). The overall sensitivity of nNO measured by VC techniques was 0.95 (95 % CI 0.91-0.97), while specificity was 0.94 (95 % CI 0.88-0.97). The positive likelihood ratio (LR+) of the test was 15.8 (95 % CI 8.1-30.6), whereas the negative likelihood ratio (LR-) was 0.06 (95 % CI 0.04-0.09). For non-VC techniques, the overall sensitivity of nNO measurement was 0.93 (95 % CI 0.89-0.96) whereas specificity was 0.95 (95 % CI 0.82-0.99). The LR+ of the test was 18.5 (95 % CI 4.6-73.8) whereas the LR- was 0.07 (95 % CI 0.04-0.12).

CONCLUSIONS

Diagnostic accuracy of nNO measurement both with VC and non-VC maneuvers is high and can be effectively employed in the clinical setting to detect PCD even in young children, thus potentiating early diagnosis. Measurement of nNO merits to be part of a revised diagnostic algorithm with the most efficacious combination of tests to achieve PCD diagnosis.

Accuracy of diagnostic testing in primary ciliary dyskinesia

Diagnosis of primary ciliary dyskinesia (PCD) lacks a “gold standard” test and is therefore based on combinations of tests including nasal nitric oxide (nNO), high-speed video microscopy analysis (HSVMA), genotyping and transmission electron microscopy (TEM). There are few published data on the accuracy of this approach.

Using prospectively collected data from 654 consecutive patients referred for PCD diagnostics we calculated sensitivity and specificity for individual and combination testing strategies. Not all patients underwent all tests.

HSVMA had excellent sensitivity and specificity (100% and 93%, respectively). TEM was 100% specific, but 21% of PCD patients had normal ultrastructure. nNO (30 nL·min⁻¹ cut-off) had good sensitivity and specificity (91% and 96%, respectively). Simultaneous testing using HSVMA and TEM was 100% sensitive and 92% specific.

In conclusion, combination testing was found to be a highly accurate approach for diagnosing PCD. HSVMA alone has excellent accuracy, but requires significant expertise, and repeated sampling or cell culture is often needed. TEM alone is specific but misses 21% of cases. nNO (≤30 nL·min⁻¹) contributes well to the diagnostic process. In isolation nNO screening at this cut-off would miss ∼10% of cases, but in combination with HSVMA could reduce unnecessary further testing. Standardisation of testing between centres is a future priority.

Combination testing in PCD diagnosis remains the most accurate approach, but standardisation is neededhttp://ow.ly/TLEDu

Technical and practical issues for tidal breathing measurements of nasal nitric oxide in children

To promote early screening of patients with suspected Primary Ciliary Dyskinesia (PCD), nasal nitric oxide (nNO) measurements during tidal breathing (TB) have been developed for children unable to ensure velum closure (VC) during breath hold or expiration against resistance. To investigate technical and practical issues related to TB-nNO methods in children referred for suspected or asserted PCD, we recorded, in a prospective multicenter study, TB-nNO (calculated as the mean of 5 peaks, 10 or 30 sec during tidal breathing) and VC-nNO when available. We studied 142 children (PCD diagnosis asserted in 47, excluded in 39). Nasal NO values were significantly different according to methods, VC-nNO being higher than TB-nNO (TB-nNO 5 peaks higher than mean of 10 or 30 sec). Specificity (90-94%) and sensitivity (86-97%) were similar between TB-nNO and VC-nNO methods. Age was more correlated with VC-nNO than with TB-nNO. TB-nNO could differ between the two nostrils by more than 10% (or 10 ppb when nNO absolute value lower 100 ppb) in 32-43% of the tested children, according to the different tidal breathing values, and was reproducible in the long term but influenced by ambient NO. Despite TB-nNO values being lower than VC-nNO, TB-nNO was found to be as discriminant for PCD, and probably more discriminant in children less than 8 years old, as the VC method. These results were obtained using the chemiluminescence technique which allows an easier assessment of relevant factors such as nasal permeability and ambient NO than the electrochemical technique.

Application of nitric oxide measurements in clinical conditions beyond asthma

Fractional exhaled nitric oxide (FeNO) is a convenient, non-invasive method for the assessment of active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid diagnosis and monitoring in several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory, infectious, and/or immunological conditions. In this short review, we provide an overview of several clinical studies and discuss the status of potential applications of NO measurements in clinical conditions beyond asthma.

Nasal nitric oxide screening for primary ciliary dyskinesia: systematic review and meta-analysis

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.

Diagnosis and management of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is an inherited autosomal-recessive disorder of motile cilia characterised by chronic lung disease, rhinosinusitis, hearing impairment and subfertility. Nasal symptoms and respiratory distress usually start soon after birth, and by adulthood bronchiectasis is invariable. Organ laterality defects, usually situs inversus, occur in ∼50% of cases. The estimated prevalence of PCD is up to ∼1 per 10,000 births, but it is more common in populations where consanguinity is common. This review examines who to refer for diagnostic testing. It describes the limitations surrounding diagnosis using currently available techniques and considers whether recent advances to genotype patients with PCD will lead to genetic testing and screening to aid diagnosis in the near future. It discusses the challenges of monitoring and treating respiratory and ENT disease in children with PCD.