Sweat conductivity: An accurate diagnostic test for cystic fibrosis?

Diagnosing cystic fibrosis in low- and middle-income countries: challenges and strategies

BACKGROUND

Cystic Fibrosis is caused by recessively inherited variants of the cystic fibrosis transmembrane regulator. It is associated with diverse clinical presentations that can affect the respiratory, digestive, and reproductive systems and inhibit nutrient absorption and growth.

MAIN BODY

The current estimation of people affected by Cystic Fibrosis is likely underestimated as this disease remains undiagnosed in countries with limited diagnostic capacity. Recent evidence indicates that Cystic Fibrosis is more common than initially thought and is likely underreported in low- and middle-income countries. The sweat chloride test remains the gold standard for diagnosing Cystic Fibrosis. However, the costs of commercially available instruments, consumables, and laboratory reagents remain relatively high for widespread implementation in low- and middle-income countries.

CONCLUSION

Alternative, cost-effective, and simpler approaches to sweat electrolyte measurement, may present more feasible options for CF diagnosis in the setting of low- and middle-income countries. Novel low-cost, point-of-care innovations for measuring sweat chloride should be explored and further validated as suitable alternatives. It will be important to consider how to implement these options and adjust the diagnostic algorithm to meet the needs of low- and middle-income countries. Future Cystic Fibrosis research in low- and middle-income countries should focus on finding a lower-cost and resource-intensive pathway for CF screening and diagnosis to improve its availability.

Diagnosing Cystic Fibrosis in the 21st Century-A Complex and Challenging Task

Cystic fibrosis (CF) is a chronic and potentially life-threatening condition, wherein timely diagnosis assumes paramount significance for the prompt initiation of therapeutic interventions, thereby ameliorating pulmonary function, addressing nutritional deficits, averting complications, mitigating morbidity, and ultimately enhancing the quality of life and extending longevity. This review aims to amalgamate existing knowledge to provide a comprehensive appraisal of contemporary diagnostic modalities pertinent to CF in the 21st century. Deliberations encompass discrete delineations of each diagnostic modality and the elucidation of potential diagnostic quandaries encountered in select instances, as well as the delineation of genotype-phenotype correlations germane to genetic counseling endeavors. The synthesis underscores that, notwithstanding the availability and strides in diagnostic methodologies, including genetic assays, the sweat test (ST) retains its position as the preeminent diagnostic standard for CF, serving as a robust surrogate for CFTR functionality. Prospective clinical investigations in the realm of CF should be orchestrated with the objective of discerning novel diagnostic modalities endowed with heightened specificity and sensitivity.

Normative data for aquagenic wrinkling of palms in children 1-15 years of age: A cross-sectional study

BACKGROUND

Aquagenic wrinkling of palms (AWP) is emerging as a screening test for cystic fibrosis (CF). There is lack of normative data for the same in our population.

OBJECTIVES

To generate normative data for AWP in children 1-15 years of age and to describe the factors associated with it.

METHODS

Children aged 1-15 years were enrolled after obtaining informed consent and assent of the parent and child based on age. Information regarding age, gender, anthropometry, indications for visiting hospital and drug intake were noted down. Wrinkling test was done using distilled water maintained in room temperature. Sweat chloride analysis was done using Nano duct sweat analysis system for children having AWP within 3 min. The mean/median time to wrinkle was noted and presented as centile curves after smoothing.

RESULTS

The mean (SD) and median (interquartile range [IQR]) aquagenic wrinkling time in children 1-15 years of age was 4.88 (1.066) and 5 (4-5.75) minutes respectively. The mean (SD) and median (IQR) time for AWP was 4.78 (1.076) and 5 (4-5) minutes respectively for boys and 4.98 (1.048) and 5 (4-6) minutes, respectively for girls. The time taken to wrinkle was observed to increase with age. Males have earlier AWP than females. There was no association between AWP and anthropometry or sweat chloride levels.

CONCLUSION

We have estimated the normative data for AWP in children 1-15 years of age which can be used for CF screening in children with typical clinical features from resource limited settings.

Sweat conductivity diagnostic accuracy for cystic fibrosis: a systematic review and meta-analysis

OBJECTIVE

We conducted a systematic review and meta-analysis of diagnostic test accuracy studies to summarise the properties of sweat conductivity (SC) to rule in/out cystic fibrosis (CF).

DATA SOURCE

We searched PubMed, Embase, Web of Science, Google Scholar, SciELO and LILACS up to 13 March 2023.

STUDY SELECTION

We selected prospective and retrospective diagnostic test accuracy studies which compared SC, measured through two well-established and commercially available devices, that is, Nanoduct or Sweat-Chek Analyser, to quantitative measurement of sweat chloride.

MAIN OUTCOME MEASURES

Pooled sensitivity, specificity, positive likelihood ratio (+LR) and negative likelihood ratio (-LR), and their corresponding 95% CIs.

DATA EXTRACTION AND SYNTHESIS

The Preferred Reporting Items for a Systematic Review and Meta-analysis of Diagnostic Test Accuracy Studies guidelines were followed. Data were extracted by one reviewer and checked by another. The hierarchical summary receiver operating characteristics model was used to estimate diagnostic test accuracy.

RESULTS

Ten studies involving 8286 participants were included. The pooled estimates of sensitivity, specificity, +LR and -LR were 0.97 (95% CI 0.94 to 0.98), 0.99 (95% CI 0.98 to 0.99), 171 (95% CI 58 to 500) and 0.02 (95% CI 0.01 to 0.05), respectively. Sensitivity analyses did not reveal a substantial impact of study-level factors on the results, such as study quality, cut-off values for a positive test, study sample size and participant age group. The quality of evidence was considered moderate.

CONCLUSION

SC demonstrated excellent diagnostic performance. In addition, its accuracy parameters suggest its role as an alternative to the sweat test for CF diagnosis.

PROSPERO REGISTRATION NUMBER

CRD42022284504.

Sweat conductivity for diagnosing cystic fibrosis after positive newborn screening: prospective, diagnostic test accuracy study

OBJECTIVE

To assess the accuracy of sweat conductivity among newborns and very young infants.

DESIGN

Prospective, population-based, diagnostic test accuracy study.

SETTING

Public Statewide Newborn Screening Programme where the incidence rate of cystic fibrosis (CF) is ≈1:11 000.

PATIENTS

Newborns and very young infants with positive two-tiered immunoreactive trypsinogen.

INTERVENTIONS

Sweat conductivity and sweat chloride were performed simultaneously, on the same day and facility by independent technicians, with the cut-off values of 80 mmol/L and 60 mmol/L, respectively.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive and negative predictive values (PPV and NPV), overall accuracy, positive and negative likelihood ratios (+LR, -LR) and post (sweat conductivity (SC)) test probability were calculated to assess SC performance.

RESULTS

1193 participants were included, 68 with and 1108 without CF, and 17 with intermediate values. The mean (SD) age was 48 (19.2) days, ranging from 15 to 90 days. SC yielded sensitivity of 98.5% (95% CI 95.7 to 100), specificity of 99.9% (95% CI 99.7 to 100), PPV of 98.5% (95% CI 95.7 to 100) and NPV of 99.9% (95% CI 99.7 to 100), overall accuracy of 99.8% (95% CI 99.6 to 100), +LR of 1091.7 (95% CI 153.8 to 7744.9) and -LR of 0.01 (95% CI 0.00 to 0.10). After a positive and negative sweat conductivity result, the patient's probability of CF increases around 350 times and drops to virtually zero, respectively.

CONCLUSION

Sweat conductivity had excellent accuracy in ruling in or ruling out CF after positive two-tiered immunoreactive trypsinogen among newborns and very young infants.

Full-Cut Manufacture of Skin-Interfaced Microfluidic Patch with Copper Electrode for In Situ Admittance Sensing of Sweat Rate

Sweat-rate measurement has received more and more attention, especially for specific groups, such as athletes, soldiers and manual workers, due to their excessive sweat loss under prolonged intense heat stress, which increases the risk of dehydration and electrolyte imbalance. The highly effective manufacture of a sweat-sensing device is essential to its wide range of applications in perspiration-related physiological information detection. In this work, we propose a simple and cost-effective strategy for the manufacture of a microfluidic sweat-rate-sensing patch via laser cutting and transfer printing technology. A copper foil tape is used as the electrode for in situ admittance based sweat-rate-sensing. The detection circuits and measurement conditions are optimized to prevent the negative effect of an electrochemical reaction between a copper electrode and sweat for precise admittance measurement. In vitro and on-body experiments demonstrate that the copper electrode is applicable for admittance-based sweat sensing and is capable of achieving equivalent sensing accuracy as a gold electrode and that the proposed sensor structure can perform consecutive and accurate sweat-rate-sensing and facilitates a significant increase in manufacturing efficiency.

Genetic spectrum of Chinese children with cystic fibrosis: comprehensive data analysis from the main referral centre in China

BACKGROUND AND OBJECTIVES

Cystic fibrosis (CF) is a heterogeneous disease with a diverse genetic spectrum among populations. Few patients with CF of Chinese origin have been reported worldwide. The objective of this study is to characterise the genotypic features of CF in Chinese children.

METHODS

We recruited and characterised the genetic manifestations of 103 Chinese children with CF in Beijing Children's Hospital from 2010 to 2022. Whole-exome sequencing were performed to define the genotypes. Meanwhile, other 99 genetically confirmed patients with Chinese origin described in 45 references were also summarised.

RESULTS

158 different variants including 23 novel observations were identified after sequencing. The majority of CFTR variants (82.3%) in Chinese have been observed only once or twice. 43.7% of the variants were only identified in patients of Chinese origin. The c.2909G>A(p.Gly970Asp), c.1766+5G>T and c.1657C>T(p.Arg553X) were the most frequent variants among Chinese patients, with allele frequency of 12.1%, 5.4% and 3.6%, respectively. The first two variants both showed significant Chinese ethnic tendency, while the latter one most likely came from Europeans for historical reasons. They also demonstrated significant differences in geographical distribution. c.1521_1523delCTT(p.F508del) was rarely observed in patients of pure Chinese origin, with an allele frequency of 1.8%. Two de novo variants (c.960dupA[p.Ser321IlefsX43] and c.2491-2A>G) and two deep-intronic variants (c.3718-2477C>T and c.3874-4522A>G) were identified, which were also quite rare among Chinese.

CONCLUSIONS

The genetic spectrum of CF in Chinese is unique and quite different from that observed in Caucasians. The geographical distributions of the most frequent variants were reported for the first time.

Clinical findings of patients with cystic fibrosis according to newborn screening results

BACKGROUND

Cystic fibrosis (CF) is a lethal recessive genetic disease caused by loss of function associated with mutations in the CF trans-membrane conductance regulator. It is highly prevalent (approximately 1 in 3,500) in Caucasians. The aim of this study was to compare demographic and clinical features, diagnostic tests, treatments, and complications of patients with CF whose newborn screening (NBS) with twice-repeated immune reactive trypsinogen testing was positive, normal, and not performed.

METHODS

In this study, 359 of all 1,488 CF patients recorded in the CF Registry of Turkey in 2018, who had been born through the process of NBS, were evaluated. Demographic and clinical features were compared in patients diagnosed with positive NBS (Group 1), normal (Group 2), or without NBS (Group 3).

RESULTS

In Group 1, there were 299 patients, in Group 2, there were 40 patients, and in Group 3, there were 20 patients. Among all patients, the median age at diagnosis was 0.17 years. The median age at diagnosis was higher in Groups 2 and 3 than in Group 1 (P = 0.001). Fecal elastase results were higher in Group 2 (P = 0.033). The weight z-score was lower and chronic Staphylococcus aureus infection was more common in Group 3 (P = 0.017, P = 0.004, respectively).

CONCLUSIONS

Frequency of growth retardation and chronic S. aureus infection can be reduced with an early diagnosis using NBS. In the presence of clinical suspicion in patients with normal NBS, further analyses such as genetic testing should be performed, especially to prevent missing patients with severe mutations.

Sweat testing in the modern era: A national survey of sweat testing practice in the Republic of Ireland

BACKGROUND

The sweat test has been the "gold standard" diagnostic test for cystic fibrosis for more than 40 years. We hypothesized that there would be a change in the pattern of sweat testing in Ireland since the introduction of cystic fibrosis newborn screening in 2011, when practices were last reviewed. This is a follow up survey looking at sweat testing numbers and practices.

METHODS

A national survey compiled data on sweat collection, conductivity and sweat chloride testing in all hospitals previously identified as performing sweat tests.

RESULTS

All 13 centres in Ireland performing sweat testing in 2018 responded to the survey (100% return rate). Our results indicate that 1007 sweat tests were performed in 2018 compared to 2555 in 2011, equating to a 61% reduction. Seven out of 13 centres are performing less than 50 sweat tests per year. Nine out of 13 centres (69%) had a sweat test failure rate greater than the recommended allowable rate of ≤ 10%. We detected a trend of sweat testing in patients with an existing diagnosis of CF who had commenced cystic fibrosis transmembrane conductance regulator (CFTR) modulators.

CONCLUSIONS

There has been a significant reduction in the number of sweat tests performed in Ireland since the introduction of newborn screening for CF. There remains a lack of standardisation in many aspects of the service ranging from sample collection to reporting of results. We have identified a new trend of sweat testing in the cystic fibrosis transmembrane conductance regulator modulator era.

Hand-drawn electrode based disposable paper chip for artificial sweat analysis using impedance spectroscopy

Low cost, disposable paper based electrical sensor to examine the analyte concentration in an extremely small volume of sample solution is essential for environmental and healthcare applications. For the development of paper based devices, sophisticated instruments are essential to pattern electrode on the top surface of the paper. In most cases, such fabricated device results in direct contact with the analyte solution on the surface of the electrode during electrical detection and leads to high electrical double layer capacitance. In this work, we have focused to reduce the double layer capacitance by fabricating hand drawn electrode paper sensor utilising the reverse side of the paper. This design acts as a sample storage and facilitate impedimetric sensing of ionic concentration of analyte solution using a few microlitre. Droplet formation at the bottom of the paper in the confined area is visually monitored to reduce sample wastage. The interaction between two different electrode materials (graphite and silver) on the paper substrate with the different volume and concentration of the electrolyte is analysed to improve the robustness and sensitivity of the measurement. Simultaneously, we observed a reduction in the electrical double layer effect on the low sample volumes. The proposed paper based sensor shows the enhanced impedance stability on silver electrode patterned paper chip than graphite electrode paper chip to detect the different ionic concentration of artificial sweat sample. Finally, it demonstrates that paper chip has great potential as a disposable diagnostics sensor in healthcare applications.

Cystic fibrosis in South Africa: spectrum of disease and determinants of outcome

Introduction

Little is known about cystic fibrosis (CF) in low- to middle-income settings. This study aimed to describe the spectrum and outcomes of CF in South Africa (SA) from the recently established SA CF registry (SACFR).

Methods

Demographic, diagnosis and clinical data were extracted from the SACFR. Cross-sectional univariable and multivariable regression analysis of best forced expiratory volume in 1 s (FEV₁; age≥6 years) and nutrition (all ages) in 2018 was conducted to investigate factors associated with severe lung disease (SLD; FEV₁ ≤3.0 z-score) and undernutrition.

Results

By December 2018, ancestry of 447 individuals included in the SACFR was Caucasian (315; 70%), mixed (87; 19%) and black African (41; 9%). Median diagnosis age was 7.6 months (IQR 2.7-37.1). Genotype was p.Phe508del homozygous (220; 49%); p.Phe508del heterozygous (144; 32%) and neither p.Phe508del or unknown Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) variant in 83 (19%); the second most frequent CFTR variant was 3120+1G>A, common in black Africans. Median age of patients in 2018 was 14.7 years (IQR 7.4-24.4). SLD was independently associated with chronic methicillin-resistant Staphylococcus aureus (MRSA) (adjusted odds ratio( aOR) 16.75; 95% CI 1.74-161.50), undernutrition (aOR 5.20; 95% CI 2.23-12.13) and age (aOR 2.23 per 10 years; 95% CI 1.50-3.31). Undernutrition was associated in univariable analysis with low weight at diagnosis, non-Caucasian ancestry, chronic P. aeruginosa infection and lower socioeconomic status.

Conclusion

Interventions targeting MRSA infection and nutrition are needed to improve CF outcomes in SA. Most people with CF in SA are eligible for highly effective CFTR modulator therapy.

Cystic fibrosis in low and middle-income countries (LMIC): A view from four different regions of the world

Cystic fibrosis (CF) has been shown to affect people all over the world. While life expectancy for people with CF has increased substantially, CF is still associated with death in infants and young children in many regions, particularly in low and middle-income countries (LMIC). These countries face significant challenges to promote CF diagnosis and improvements to CF care due to financial constraints and a significant burden of other diseases. In this review, we describe the status of CF diagnosis and care in different LMIC settings, from four different parts of the world (Brazil, South Africa, Israel and India). We highlight challenges and opportunities for CF practitioners in LMIC to improve CF care and outcomes. While early CF diagnosis is the key to optimising outcomes, newborn screening may not be feasible for countries with lower CF incidence and higher birth rates, such as India or South Africa. CF therapies and care in LMIC need to be adapted to available resources of these countries. Collaboration initiatives of the global CF community with LMIC may improve CF care in these countries. Most individuals with CF in LMIC are not benefiting from CFTR modulator treatments due to the prohibitive cost of these drugs.

Pseudo-Bartter syndrome in Chinese children with cystic fibrosis: Clinical features and genotypic findings

OBJECTIVES

To characterize the clinical and genotypic features of cystic fibrosis-associated pseudo-Bartter syndrome (CF-PBS) in Chinese children.

METHODS

We recruited and characterized the clinical manifestations of 12 Chinese children with CF-PBS. Sweat test, blood and urinary analysis, sputum culture, chest and sinus computed tomography, and abdominal ultrasonography were obtained. Whole-exome sequencing, bioinformatics analysis, and Sanger sequencing validation were performed to define the genotypes.

RESULTS

CF-PBS was accompanied by recurrent and/or persistent pneumonia (91.7%), pancreatitis (83.3%), vomiting and/or diarrhea (66.7%), failure to thrive and liver disease (58.3% respectively), among our patients. The predominant organisms found in the airways were Pseudomonas aeruginosa (83.3%) and Staphylococcus aureus (75.0%). The mean concentrations of blood gas and electrolytes were pH 7.58, bicarbonate 40.8 mmol/L, sodium 125.9 mmol/L, chloride 77.5 mmol/L, and potassium 2.6 mmol/L. A high recurrence rate (50.0%) of CF-PBS was observed despite continued electrolyte supplementation during follow-up. In all, 19 different variants of CFTR gene were identified, and 10 of these were found to be novel observations (c.262_266delTTATA[p.L88FfsX21], c.579+2insACAT, c.1210-3C>G, c.1733T>C[p.L578P], c.2236_2246delGAGGCGATACTinsAAAAATC[p.E746KfsX8], c.3068T>G [p.I1023R], c.3635delT[p.V1212AfsX16], c.3859delG[p.G1287EfsX2], c.3964-7A>G and ΔE23 [c.3718-?_3873+?del]). The c.2909G>A[p.G970D] was the most common variant, with an allele frequency of 16.6%. A homozygous genotype of c.1521_1523delCTT[p.F508del] was discovered for the first time in patients of Chinese origin.

CONCLUSIONS

In China, CF-PBS usually presents early and recurs frequently in infancy, accompanied by multiple comorbidities. Recurrence of CF-PBS in school-going patients does occur but is rare. The p.G970D is the most frequent variant, with a significant ethnic tendency of Chinese origin.

Extensive CFTR sequencing through NGS in Brazilian individuals with cystic fibrosis: unravelling regional discrepancies in the country

BACKGROUND

The Brazilian population has a tri-hybrid composition with a high degree of ethnic admixture. We hypothesized that Brazilian individuals with CF from different Brazilian regions have a specific distribution of CFTR variants.

METHODS

Individuals with CF with data available in the Patient Registry and without an established genotype were submitted to CFTR sequencing by Next Generation Sequencing (NGS) methodology, and results were anonymously incorporated to the Registry Database. Genotyping results were expressed as 'positive', 'inconclusive' or 'negative'. Logistic regression models were performed to investigate the association between demographic/clinical variables and genotyping results. Mediation analysis was conducted to estimate direct and indirect effects of Brazilian region on a binary positive genotyping response.

RESULTS

In October 2017, data from 4,654 individuals with CF were available, and 3,104(66.7%) of them had a genotyping result. A total of 236 variants (114 new variants) were identified, with F508del identified in 46% of the alleles tested. Genotyping revealed 2,002(64.5%) individuals positive, 757(24.4%) inconclusive and 345(11.1%) negative. Distribution of genotype categories was markedly different across Brazilian Regions, with greater proportions of negative individuals in the North (45%) and Northeast (26%) regions. Newborn screening (CF-NBS) and age at diagnosis were identified as mediators of the effect of Brazilian region on a positive genotyping result.

CONCLUSIONS

This large initiative of CFTR genotyping showed significant regional discrepancies in Brazil, probably related to socio-economic conditions, lack of adequate CF-NBS and poor access to reliable sweat testing. These results may be useful to indicate Regions where CF care demands more attention.

How to perform and interpret the sweat test

Cystic fibrosis (CF) is the most common life-threatening autosomal-recessive disease affecting Caucasians in the western world. The sweat test is the main diagnostic test for CF. It is indicated as part of the clinical assessment for infants that have picked up on the national neonatal screening programme. It may also be requested where clinical suspicion of a diagnosis of CF exists despite normal screening results. This article outlines the physiological basis behind sweat testing and the technical aspects of performing the test. Indications for performing the test are also considered. The article aims to provide clinicians with a guide to interpretation of results.

Sweat chloride assay by inductively coupled plasma mass spectrometry: a confirmation test for cystic fibrosis diagnosis

The current guidelines for sweat chloride analysis identify the procedures for sweat collection, but not for chloride assay, which is usually performed by methods originally not aiming at the low concentrations of chloride found in sweat. To overcome this limitation, we set up, characterized, and adopted an original inductively coupled plasma mass spectrometry (ICP-MS) method for sweat chloride determination, which was designed for its easy use in a clinical laboratory. The method was linear in the range 8.5E−3 to 272.0E−3 mM, precision exhibited a relative standard deviation < 6%, and accuracy was in the range 99.7–103.8%. Limit of blank, limit of detection, and limit of quantitation were 2.1 mM, 3.2 mM, and 7.0 mM, respectively, which correspond to real concentrations injected into the mass spectrometer of 3.9E−3 mM for LOD and 8.5E−3 mM for LOQ. At first, the method was tested on 50 healthy volunteers who exhibited a mean chloride concentration of 15.7 mM (25–75th percentile 10.1–19.3 mM, range 2.8–37.4 mM); then, it was used to investigate two patients with suspected cystic fibrosis, who exhibited sweat chloride values of 65.6 mM and 81.2 mM, respectively. Moreover, the method was cross-validated by assaying 50 samples with chloride concentration values in the range 10–131 mM, by both ICP-MS and coulometric titration, which is the technology officially used in Tuscany for cystic fibrosis newborn screening. The reference analytical performances and the relatively low cost of ICP-MS, accompanied by the advantageous cost of a single sweat chloride assay, make this technology the best candidate to provide a top reference method for the quantification of chloride in sweat. The method that we propose was optimized and validated for sweat samples ≥ 75 mg, which is the minimum amount requested by the international protocols. However, the method sensitivity and, in addition, the possibility to reduce the sample dilution factor, make possible the quantification of chloride even in samples weighting < 75 mg that are discarded according to the current guidelines.

Newborn Screening for Cystic Fibrosis in Russia: A Catalyst for Improved Care

In order to assess the effectiveness of the detection of cystic fibrosis (CF) patients by screening compared with diagnoses based on clinical manifestations, the data of the National CF Patient Registry (NCFPR) from the year 2012 (group I: children aged 6-9 years, diagnosed prior to the start of screening) were compared with the data in the NCFPR from the year 2015 (group II: children 6-9 years after the start of screening) for CF patients from the Moscow region. Homozygotes for c.1521_1523delCTT (F508del) were separately compared in both groups. The average diagnosis age, genotype, body mass index, spirometry data, pulmonary infection, medications, and presence of complications were analyzed. This study demonstrated that in the c.1521_1523delCTT (F508del) homozygote group, the patients diagnosed by screening had significant advantages over the patients born before the start of newborn screening in the diagnosis age, the number of patients with chronic Pseudomonas aeruginosa infection, the pulmonary function, and the growth in the percentiles. Newborn screening (NBS) detects nearly twice as many CF patients as the diagnostics based on clinical symptoms during the same time period. Importantly, patients will benefit from the early diagnosis of the disease and the early start of therapy.

The future of cystic fibrosis care: a global perspective

The past six decades have seen remarkable improvements in health outcomes for people with cystic fibrosis, which was once a fatal disease of infants and young children. However, although life expectancy for people with cystic fibrosis has increased substantially, the disease continues to limit survival and quality of life, and results in a large burden of care for people with cystic fibrosis and their families. Furthermore, epidemiological studies in the past two decades have shown that cystic fibrosis occurs and is more frequent than was previously thought in populations of non-European descent, and the disease is now recognised in many regions of the world. The Lancet Respiratory Medicine Commission on the future of cystic fibrosis care was established at a time of great change in the clinical care of people with the disease, with a growing population of adult patients, widespread genetic testing supporting the diagnosis of cystic fibrosis, and the development of therapies targeting defects in the cystic fibrosis transmembrane conductance regulator (CFTR), which are likely to affect the natural trajectory of the disease. The aim of the Commission was to bring to the attention of patients, health-care professionals, researchers, funders, service providers, and policy makers the various challenges associated with the changing landscape of cystic fibrosis care and the opportunities available for progress, providing a blueprint for the future of cystic fibrosis care. The discovery of the CFTR gene in the late 1980s triggered a surge of basic research that enhanced understanding of the pathophysiology and the genotype-phenotype relationships of this clinically variable disease. Until recently, available treatments could only control symptoms and restrict the complications of cystic fibrosis, but advances in CFTR modulator therapies to address the basic defect of cystic fibrosis have been remarkable and the field is evolving rapidly. However, CFTR modulators approved for use to date are highly expensive, which has prompted questions about the affordability of new treatments and served to emphasise the considerable gap in health outcomes for patients with cystic fibrosis between high-income countries, and low-income and middle-income countries (LMICs). Advances in clinical care have been multifaceted and include earlier diagnosis through the implementation of newborn screening programmes, formalised airway clearance therapy, and reduced malnutrition through the use of effective pancreatic enzyme replacement and a high-energy, high-protein diet. Centre-based care has become the norm in high-income countries, allowing patients to benefit from the skills of expert members of multidisciplinary teams. Pharmacological interventions to address respiratory manifestations now include drugs that target airway mucus and airway surface liquid hydration, and antimicrobial therapies such as antibiotic eradication treatment in early-stage infections and protocols for maintenance therapy of chronic infections. Despite the recent breakthrough with CFTR modulators for cystic fibrosis, the development of novel mucolytic, anti-inflammatory, and anti-infective therapies is likely to remain important, especially for patients with more advanced stages of lung disease. As the median age of patients with cystic fibrosis increases, with a rapid increase in the population of adults living with the disease, complications of cystic fibrosis are becoming increasingly common. Steps need to be taken to ensure that enough highly qualified professionals are present in cystic fibrosis centres to meet the needs of ageing patients, and new technologies need to be adopted to support communication between patients and health-care providers. In considering the future of cystic fibrosis care, the Commission focused on five key areas, which are discussed in this report: the changing epidemiology of cystic fibrosis (section 1); future challenges of clinical care and its delivery (section 2); the building of cystic fibrosis care globally (section 3); novel therapeutics (section 4); and patient engagement (section 5). In panel 1, we summarise key messages of the Commission. The challenges faced by all stakeholders in building and developing cystic fibrosis care globally are substantial, but many opportunities exist for improved care and health outcomes for patients in countries with established cystic fibrosis care programmes, and in LMICs where integrated multidisciplinary care is not available and resources are lacking at present. A concerted effort is needed to ensure that all patients with cystic fibrosis have access to high-quality health care in the future.

Proof of concept for identifying cystic fibrosis from perspiration samples

The gold standard for cystic fibrosis (CF) diagnosis is the determination of chloride concentration in sweat. Current testing methodology takes up to 3 h to complete and has recognized shortcomings on its diagnostic accuracy. We present an alternative method for the identification of CF by combining desorption electrospray ionization mass spectrometry and a machine-learning algorithm based on gradient boosted decision trees to analyze perspiration samples. This process takes as little as 2 min, and we determined its accuracy to be 98 ± 2% by cross-validation on analyzing 277 perspiration samples. With the introduction of statistical bootstrap, our method can provide a confidence estimate of our prediction, which helps diagnosis decision-making. We also identified important peaks by the feature selection algorithm and assigned the chemical structure of the metabolites by high-resolution and/or tandem mass spectrometry. We inspected the correlation between mild and severe CFTR gene mutation types and lipid profiles, suggesting a possible way to realize personalized medicine with this noninvasive, fast, and accurate method.

Self-powered smart patch for sweat conductivity monitoring

A self-powered skin patch for the measurement of sweat conductivity is presented. The key component of the patch consists of a paper battery that is activated upon absorption of sweat. This body fluid acts as the battery electrolyte, the conductivity of which has a direct impact on the battery-generated output power and voltage. This particular behaviour enables the operation of a very simple and robust conductivity sensor in direct current mode without needing an external power source. The device presented in this paper takes advantage of this new measurement method to develop a sweat patch for screening cystic fibrosis that operates with an extremely simple electronic circuit that minimizes its cost and environmental impact. The patch provides an unambiguous digital result that can be read in an electrochromic display and yields 95% sensitivity and 100% specificity when tested with artificial eccrine perspiration samples.

Standardized clinical criteria and sweat test combined as a tool to diagnose Cystic Fibrosis

Context

CF is under-diagnosed in Ecuador; one out of every 11,252 live births born in Ecuador could have CF.

Aim

To analyze the clinical findings, based on previously established criteria, with the results of the sweat test, in circumstances where we do not have the routine molecular study.

Methods

Epidemiological, observational, analytic, cross-sectional study. It analyzed 180 patients clinically suspected of CF. Inclusion criteria: children of both sexes older than 30 days and younger than 12 years, who meet at least three clinical criteria suggestive for CF, outpatient and referred by a specialist physician who made a preliminary diagnosis. This is a pilot study.

Results

The combination of criteria pneumonia, chronic cough and chronic obstructive bronchial syndrome is the most frequent, with not a significant relationship with a positive sweat test. On the contrary, a significant relationship was found between the clinical combinations of pneumonia with cough and rhinosinusitis; pneumonia with cough; presence of Pseudomonas aeruginosa; and pneumonia with digital cough and clubbing, so it is recommended to perform the test in all these associations. The most frequent clinical criterion for the reference and performance of the electrolyte test in sweat is pneumonia to repeat for two or more episodes.

Conclusion

Clinical combinations of pneumonia with cough and rhinosinusitis; pneumonia with cough; presence of Pseudomonas aeruginosa; and pneumonia with digital cough and clubbing are pathognomonic for CF and indication for the sweat test. The predictive performance in CF diagnosis, defined as compatible clinical presence plus high values of chloride in sweat test, was 91.1%.

Conductive Thread-Based Textile Sensor for Continuous Perspiration Level Monitoring

Individual perspiration level indicates a person’s physical status as well as their comfort level. Therefore, continuous perspiration level measurement enables people to monitor these conditions for applications including fitness assessment, athlete physical status monitoring, and patient/elderly care. Prior work on perspiration (sweat) sensing required the user either to be static or to wear the adhesive sensor directly on the skin, which limits users’ mobility and comfort. In this paper, we present a novel conductive thread-based textile sensor that measures an individual’s on-cloth sweat quantity. The sensor consists of three conductive threads. Each conductive thread is surrounded by a braided cotton cover. An additional braided cotton cover is placed outside the three conductive threads, holding them in a position that is stable for measurement. the sensor can be embedded at various locations on a person’s clothing. When the person sweats, the cotton braids absorb the sweat and change the conductivity (resistance) between conductive threads. We used a voltage dividing circuit to measure this resistance as the sensor output (DC). We then conducted a sensor calibration to map this measured voltage to the quantity of electrolyte solution (with the same density as sweat) applied to the sensor. We used this sensor to measure individuals’ perspiration quantity and infer their perceived perspiration levels. The system is able to limit the average prediction error to 0.4 levels when compared to five pre-defined perceived perspiration levels.

Clinical characterization and diagnosis of cystic fibrosis through exome sequencing in Chinese infants with Bartter-syndrome-like hypokalemia alkalosis

Cystic fibrosis (CF) is a fatal autosomal-recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. CF is characterized by recurrent pulmonary infection with obstructive pulmonary disease. CF is common in the Caucasian population but is rare in the Chinese population. The symptoms of early-stage CF are often untypical and may sometimes manifest as Bartter syndrome (BS)-like hypokalemic alkalosis. Therefore, the ability of doctors to differentiate CF from BS-like hypokalemic alkalosis in Chinese infants is a great challenge in the timely and accurate diagnosis of CF. In China, sporadic CF has not been diagnosed in children younger than three years of age to date. Three infants, who were initially admitted to our hospital over the period of June 2013 to September 2014 with BS-like hypokalemic alkalosis, were diagnosed with CF through exome sequencing and sweat chloride measurement. The compound heterozygous mutations of the CFTR gene were detected in two infants, and a homozygous missense mutation was found in one infant. Among the six identified mutations, two are novel point mutations (c.1526G > C and c.3062C > T) that are possibly pathogenic. The three infants are the youngest Chinese patients to have been diagnosed with sporadic CF at a very early stage. Follow-up examination showed that all of the cases remained symptom-free after early intervention, indicating the potential benefit of very early diagnosis and timely intervention in children with CF. Our results demonstrate the necessity of distinguishing CF from BS in Chinese infants with hypokalemic alkalosis and the significant diagnostic value of powerful exome sequencing for rare genetic diseases. Furthermore, our findings expand the CFTR mutation spectrum associated with CF.

Brazilian guidelines for the diagnosis and treatment of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic disorder characterized by dysfunction of the CFTR gene. It is a multisystem disease that most often affects White individuals. In recent decades, various advances in the diagnosis and treatment of CF have drastically changed the scenario, resulting in a significant increase in survival and quality of life. In Brazil, the current neonatal screening program for CF has broad coverage, and most of the Brazilian states have referral centers for the follow-up of individuals with the disease. Previously, CF was limited to the pediatric age group. However, an increase in the number of adult CF patients has been observed, because of the greater number of individuals being diagnosed with atypical forms (with milder phenotypic expression) and because of the increase in life expectancy provided by the new treatments. However, there is still great heterogeneity among the different regions of Brazil in terms of the access of CF patients to diagnostic and therapeutic methods. The objective of these guidelines was to aggregate the main scientific evidence to guide the management of these patients. A group of 18 CF specialists devised 82 relevant clinical questions, divided into five categories: characteristics of a referral center; diagnosis; treatment of respiratory disease; gastrointestinal and nutritional treatment; and other aspects. Various professionals working in the area of CF in Brazil were invited to answer the questions devised by the coordinators. We used the PubMed database to search the available literature based on keywords, in order to find the best answers to these questions.

Real life practice of sweat testing in Europe

Evidence based guidelines exist for sweat testing, which remains a key component of a diagnosis of cystic fibrosis (CF), especially following newborn bloodspot screening (NBS). There are emerging challenges with respect to maintaining a valid sweat test service, notably a smaller number of sweat tests ordered in regions with established NBS programmes where Pediatricians refer less children for sweat testing, younger patients and equipment becoming obsolete. The ECFS Diagnostic Network Working Group has undertaken a comprehensive survey to better define sweat test practice across Europe. The survey was completed by 136 European respondents representing a CF center or laboratory providing a sweat test service (65% from regions with NBS for CF). There was considerable variance in practice, often not consistent with guidelines. In particular collection of sweat from two sites was rarely reported in European centres in contrast to US guidelines. There was a range of different references quoted for cut-off for both a positive and intermediate test. Most responses suggest cost is becoming an increasing issue and is not sufficiently reimbursed. This work will inform best practice guidelines and resources to sustain and improve sweat testing in Europe.

Comparison between Field Effect Transistors and Bipolar Junction Transistors as Transducers in Electrochemical Sensors

Field effect transistors (FET) have been widely used as transducers in electrochemical sensors for over 40 years. In this report, a FET transducer is compared with the recently proposed bipolar junction transistor (BJT) transducer. Measurements are performed on two chloride electrochemical sensors that are identical in all details except for the transducer device type. Comparative measurements show that the transducer choice significantly impacts the electrochemical sensor characteristics. Signal to noise ratio is 20 to 2 times greater for the BJT sensor. Sensitivity is also enhanced: BJT sensing signal changes by 10 times per pCl, whereas the FET signal changes by 8 or less times. Also, sensor calibration curves are impacted by the transducer choice. Unlike a FET sensor, the calibration curve of the BJT sensor is independent of applied voltages. Hence, a BJT sensor can make quantitative sensing measurements with minimal calibration requirements, an important characteristic for mobile sensing applications. As a demonstration for mobile applications, these BJT sensors are further investigated by measuring chloride levels in artificial human sweat for potential cystic fibrosis diagnostic use. In summary, the BJT device is demonstrated to be a superior transducer in comparison to a FET in an electrochemical sensor.

Skin Biomarkers for Cystic Fibrosis: A Potential Non-Invasive Approach for Patient Screening

BACKGROUND

Cystic fibrosis (CF) is a disabling genetic disease with an increased prevalence in European heritage populations. Currently, the most used technique for collection of CF samples and diagnosis is provided through uncomfortable tests, with uncertain results, mostly based on chloride concentration in sweat. Since CF mutation induces many metabolic changes in patients, exploring these alterations might be an alternative to visualize potential biomarkers that could be used as interesting tools for further diagnostic upgrade, prioritizing simplicity, low cost, and quickness.

METHODS

This contribution describes an accurate strategy to provide potential biomarkers related to CF, which may be understood as a potential tool for new diagnostic approaches and/or for monitoring disease evolution. Therefore, the present proposal consists of using skin imprints on silica plates as a way of sample collection, followed by direct-infusion high-resolution mass spectrometry and multivariate data analysis, intending to identify metabolic changes in skin composition of CF patients.

RESULTS

Metabolomics analysis allowed identifying chemical markers that can be traced back to CF in patients' skin imprints, differently from control subjects. Seven chemical markers from several molecular classes were elected, represented by bile acids, a glutaric acid derivative, thyrotropin-releasing hormone, an inflammatory mediator, a phosphatidic acid, and diacylglycerol isomers, all reflecting metabolic disturbances that occur due to of CF.

CONCLUSION

The comfortable method of sample collection combined with the identified set of biomarkers represent potential tools that open the range of possibilities to manage CF and follow the disease evolution. This exploratory approach points to new perspectives about the development of diagnostic assay using biomarkers and the management CF.

A paper-based skin patch for the diagnostic screening of cystic fibrosis

A thin and flexible paper-based skin patch was developed for the diagnostic screening of cystic fibrosis. It utilized a unique combination of both anion exchange and pH test papers to enable the quantitative, colorimetric and on-skin detection of sweat anions.

Sweat conductivity and coulometric quantitative test in neonatal cystic fibrosis screening

OBJECTIVE

To compare the results obtained with the sweat test using the conductivity method and coulometric measurement of sweat chloride in newborns (NBs) with suspected cystic fibrosis (CF) in the neonatal screening program.

METHODS

The sweat test was performed simultaneously by both methods in children with and without CF. The cutoff values to confirm CF were >50 mmol/L in the conductivity and >60 mmol/L in the coulometric test.

RESULTS

There were 444 infants without CF (185 males, 234 females, and 24 unreported) submitted to the sweat test through conductivity and coulometric measurement simultaneously, obtaining median results of 32 mmol/L and 12 mmol/L, respectively. For 90 infants with CF, the median values of conductivity and coulometric measurement were 108 mmol/L and 97 mmol/L, respectively. The false positive rate for conductivity was 16.7%, and was higher than 50 mmol/L in all patients with CF, which gives this method a sensitivity of 100% (95% CI: 93.8-97.8), specificity of 96.2% (95% CI: 93.8-97.8), positive predictive value of 83.3% (95% CI: 74.4-91.1), negative predictive value of 100% (95% CI: 90.5-109.4), and 9.8% accuracy. The correlation between the methods was r=0.97 (p>0.001). The best suggested cutoff value was 69.0 mmol/L, with a kappa coefficient=0.89.

CONCLUSION

The conductivity test showed excellent correlation with the quantitative coulometric test, high sensitivity and specificity, and can be used in the diagnosis of CF in children detected through newborn screening.

2014 year in review: Cystic fibrosis

In this article, we highlight cystic fibrosis (CF) research published in Pediatric Pulmonology during 2014, as well as related articles published in other journals.

Novel outcome measures for clinical trials in cystic fibrosis

Cystic fibrosis (CF) is a common inherited condition caused by mutations in the gene encoding the CF transmembrane regulator protein. With increased understanding of the molecular mechanisms underlying CF and the development of new therapies there comes the need to develop new outcome measures to assess the disease, its progression and response to treatment. As there are limitations to the current endpoints accepted for regulatory purposes, a workshop to discuss novel endpoints for clinical trials in CF was held in Anaheim, California in November 2011. The pros and cons of novel outcome measures with potential utility for evaluation of novel treatments in CF were critically evaluated. The highlights of the 2011 workshop and subsequent advances in technologies and techniques that could be used to inform the development of clinical trial endpoints are summarized in this review. Pediatr Pulmonol. © 2014 The Authors. Pediatric Pulmonology published by Wiley Periodicals, Inc.

Using skin for drug delivery and diagnosis in the critically ill

Skin offers easy access, convenience and non-invasiveness for drug delivery and diagnosis. In principle, these advantages of skin appear to be attractive for critically ill patients given potential difficulties that may be associated with oral and parenteral access in these patients. However, the profound changes in skin physiology that can be seen in these patients provide a challenge to reliably deliver drugs or provide diagnostic information. Drug delivery through skin may be used to manage burn injury, wounds, infection, trauma and the multisystem complications that rise from these conditions. Local anaesthetics and analgesics can be delivered through skin and may have wide application in critically ill patients. To ensure accurate information, diagnostic tools require validation in the critically ill patient population as information from other patient populations may not be applicable.