Clinical evaluation of the Nanoduct sweat test system in the diagnosis of cystic fibrosis after newborn screening

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.

Single-centre prospective evaluation of the first 5 years of cystic fibrosis newborn screening in Germany

Background

In 2016, nationwide cystic fibrosis newborn screening (CFNS) was newly implemented in Germany, using an immunoreactive trypsin/pancreatitis-associated protein/DNA screening algorithm that differs from most other nationwide screening programmes.

Methods

We analysed real-life feasibility of the confirmation process with respect to our pre-specified procedural objectives. These included overall accuracy through false-negative and false-positive results, effectiveness of the Bavarian tracking system, and accuracy of Macroduct and Nanoduct sweat conductivity compared with quantitative chloride determination. All consecutive CFNS-positive newborns assigned to our CF centre and born between 1 September 2016 and 31 August 2021 (n=162) were included.

Results

The German CFNS was feasible at our CF centre as all procedural objectives were met. The positive predictive value (PPV) of positive CFNS was low (0.23) and two initially negatively screened children were later diagnosed with CF. The tracking system was highly efficient with a 100% tracking rate. The Macroduct and Nanoduct systems had comparable success rates (93.2% versus 95.9%). Importantly, conductivity via Macroduct was more accurate than via Nanoduct (zero and four false-positive newborns, respectively).

Conclusions

CF confirmation diagnostics of neonates in a certified regional CF centre was well managed in daily routine. The PPV of the German CFNS needs to be improved, e.g. by extending the DNA analysis within the screening algorithm and by increasing the number of variants tested. The Bavarian tracking system can serve as a successful model for other tracking systems. We preferred the Macroduct system because of its more accurate sweat conductivity readings.

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.

Exploring the Potential of Nanotechnology in Pediatric Healthcare: Advances, Challenges, and Future Directions

The utilization of nanotechnology has brought about notable advancements in the field of pediatric medicine, providing novel approaches for drug delivery, disease diagnosis, and tissue engineering. Nanotechnology involves the manipulation of materials at the nanoscale, resulting in improved drug effectiveness and decreased toxicity. Numerous nanosystems, including nanoparticles, nanocapsules, and nanotubes, have been explored for their therapeutic potential in addressing pediatric diseases such as HIV, leukemia, and neuroblastoma. Nanotechnology has also shown promise in enhancing disease diagnosis accuracy, drug availability, and overcoming the blood-brain barrier obstacle in treating medulloblastoma. It is important to acknowledge that while nanotechnology offers significant opportunities, there are inherent risks and limitations associated with the use of nanoparticles. This review provides a comprehensive summary of the existing literature on nanotechnology in pediatric medicine, highlighting its potential to revolutionize pediatric healthcare while also recognizing the challenges and limitations that need to be addressed.

3D Printed Skin-Wash Sampler for Sweat Sampling in Cystic Fibrosis Diagnosis Using Capillary Electrophoretic Ion Ratio Analysis

Sweat chloride analysis is one of the important approaches in cystic fibrosis diagnosis. The commonly used Macroduct method to acquire sweat samples is semi-invasive, time consuming and expensive. Furthermore, this method often fails to collect a sufficient amount of sweat in newborns due to the insufficient sweating rate. In this work, we present a novel, simple, 3D-printed sampling device that is used to collect sweat specimens completely noninvasively in less than one minute. The device has a flow-through channel adjacent to the skin surface, through which 500 µL of deionized water is flushed and the spontaneously formed sweat on the skin in the channel area is washed into a plastic vial. The developed skin-wash procedure is a single step operation, is completely noninvasive and it always produces a sweat specimen. The ions from the skin-wash are subsequently analyzed by capillary electrophoresis with contactless conductivity detection and selected ion ratio (Cl−/K+) or ((Cl− + Na+)/K+) is used as a cut-off value to diagnose cystic fibrosis patients with sensitivity and specificity comparable to the conventional Macroduct method.

Electrical aspects of skin as a pathway to engineering skin devices

Skin is one of the indispensable organs for life. The epidermis at the outermost surface provides a permeability barrier to infectious agents, chemicals, and excessive loss of water, while the dermis and subcutaneous tissue mechanically support the structure of the skin and appendages, including hairs and secretory glands. The integrity of the integumentary system is a key for general health, and many techniques have been developed to measure and control this protective function. In contrast, the effective skin barrier is the major obstacle for transdermal delivery and detection. Changes in the electrical properties of skin, such as impedance and ionic activity, is a practical indicator that reflects the structures and functions of the skin. For example, the impedance that reflects the hydration of the skin is measured for quantitative assessment in skincare, and the current generated across a wound is used for the evaluation and control of wound healing. Furthermore, the electrically charged structure of the skin enables transdermal drug delivery and chemical extraction. This paper provides an overview of the electrical aspects of the skin and summarizes current advances in the development of devices based on these features.

Sweat Testing and Recent Advances

Cystic fibrosis (CF) is the most common fatal genetic disease of the Caucasian population. Sweat testing is the principal diagnostic test for CF, and it is used for the evaluation of infants with positive CF newborn screening (NBS) and in patients with clinical findings suggesting CF. This article describes the classical sweat test method in detail and also provides an overwiew of recent advances.

Soft, skin-interfaced sweat stickers for cystic fibrosis diagnosis and management

The concentration of chloride in sweat remains the most robust biomarker for confirmatory diagnosis of cystic fibrosis (CF), a common life-shortening genetic disorder. Early diagnosis via quantitative assessment of sweat chloride allows prompt initiation of care and is critically important to extend life expectancy and improve quality of life. The collection and analysis of sweat using conventional wrist-strapped devices and iontophoresis can be cumbersome, particularly for infants with fragile skin, who often have insufficient sweat production. Here, we introduce a soft, epidermal microfluidic device ("sweat sticker") designed for the simple and rapid collection and analysis of sweat. Intimate, conformal coupling with the skin supports nearly perfect efficiency in sweat collection without leakage. Real-time image analysis of chloride reagents allows for quantitative assessment of chloride concentrations using a smartphone camera, without requiring extraction of sweat or external analysis. Clinical validation studies involving patients with CF and healthy subjects, across a spectrum of age groups, support clinical equivalence compared to existing device platforms in terms of accuracy and demonstrate meaningful reductions in rates of leakage. The wearable microfluidic technologies and smartphone-based analytics reported here establish the foundation for diagnosis of CF outside of clinical settings.

Rethinking the causes of pilonidal sinus disease: a matched cohort study

Our understanding of pilonidal sinus disease (PSD) is based on a paper published 29 years ago by Karydakis. Since then, surgeons have been taught that hair more easily penetrates wet skin, leading to the assumption that sweating promotes PSD. This postulate, however, has never been proven. Thus we used pilocarpine iontophoresis to assess sweating in the glabella sacralis. 100 patients treated for PSD and 100 controls were matched for sex, age and body mass index (BMI). Pilocarpine iontophoresis was performed for 5 min, followed by 15 min of sweat collection. PSD patients sweated less than their matched pairs (18.4 ± 1.6 µl vs. 24.2 ± 2.1 µl, p = 0.03). Men sweated more than women (22.2 ± 1.2 µl vs. 15.0 ± 1.0 µl in non-PSD patients (p < 0.0001) and 20.0 ± 1.9 µl vs. 11.9 ± 2.0 µl in PSD patients (p = 0.051)). And regular exercisers sweated more than non-exercisers (29.1 ± 2.9 µl vs. 18.5 ± 1.6 µl, p = 0.0006 for men and 20.7 ± 2.3 µl vs. 11.4 ± 1.4 µl, p = 0.0005 for women). PSD patients sweat less than matched controls. Thus sweating may have a protective effect in PSD rather than being a risk factor.

Skin wipe test: A simple, inexpensive, and fast approach in the diagnosis of cystic fibrosis

OBJECTIVE

To assess the performance of a newly developed skin wipe test (SWT) for the diagnosis of cystic fibrosis (CF).

STUDY DESIGN

Spontaneously formed sweat from the forearm was wiped by a cotton swab moistened with 100 µL of deionized (DI) water and extracted into 400 µL of DI water (SWT). The conventional Macroduct sweat test (ST) was performed simultaneously. SWT samples of 114 CF patients, 76 healthy carriers, and 58 controls were analyzed by capillary electrophoresis with contactless conductivity detection and Cl^- /K⁺ and (Cl^-  + Na⁺ )/K⁺ ion ratios were evaluated. Chloride concentrations from Macroduct ST were analyzed coulometrically.

RESULTS

Analysis of 248 SWT samples and simultaneous Macroduct ST samples showed comparable method performance. Two ion ratios, Cl^- /K⁺ and (Cl^-  + Na⁺ )/K⁺ , from the SWT samples and Cl^- values from the ST samples were evaluated to diagnose CF. Sensitivity of the SWT method using the Cl^- /K⁺ ratio (cutoff value 3.9) was 93.9%, compared to 99.1% when using the (Cl^-  + Na⁺ )/K⁺ ratio (cutoff value 5.0) and 98.3% in using Macroduct Cl^- (cutoff value higher or equal to 60 mmol/L). The methods' specificities were 97.8%, 94.0%, and 100.0%, respectively.

CONCLUSIONS

The developed SWT method with capillary electrophoretic analysis for CF diagnosis performs comparably to the conventional Macroduct ST. The SWT method is simple, fast, inexpensive, and completely noninvasive. Use of an ion ratio in obtained SWT samples is proposed as a new diagnostic parameter that shows significant promise in CF diagnostics.

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.

Processing Newborn Bloodspot Screening Results for CF

Every newborn bloodspot screening (NBS) result for cystic fibrosis (CF) consists of two parts: a screening part in the laboratory and a clinical part in a CF centre. When introducing an NBS programme, more attention is usually paid to the laboratory part, especially which algorithm is most suitable for the region or the country. However, the clinical part, how a positive screening result is processed, is often underestimated and can have great consequences for the affected child and their parents. A clear algorithm for the diagnostic part in CF centres is also important and influences the performance of a CF NBS programme. The processing of a positive screening result includes the initial information given to the parents, the invitation to the sweat test, what to do if a sweat test fails, information about the results of the sweat test, the inconclusive diagnosis and the carrier status, which is handled differently from country to country. The time until the definitive diagnosis and adequate information is given, is considered by the parents and the CF team as the most important factor. The communication of a positive NBS result is crucial. It is not a singular event but rather a process that includes ensuring the appropriate clinicians are aware of the result and that families are informed in the most efficient and effective manner to facilitate consistent and timely follow-up.

Cyber-Physiochemical Interfaces

Living things rely on various physical, chemical, and biological interfaces, e.g., somatosensation, olfactory/gustatory perception, and nervous system response. They help organisms to perceive the world, adapt to their surroundings, and maintain internal and external balance. Interfacial information exchanges are complicated but efficient, delicate but precise, and multimodal but unisonous, which has driven researchers to study the science of such interfaces and develop techniques with potential applications in health monitoring, smart robotics, future wearable devices, and cyber physical/human systems. To understand better the issues in these interfaces, a cyber-physiochemical interface (CPI) that is capable of extracting biophysical and biochemical signals, and closely relating them to electronic, communication, and computing technology, to provide the core for aforementioned applications, is proposed. The scientific and technical progress in CPI is summarized, and the challenges to and strategies for building stable interfaces, including materials, sensor development, system integration, and data processing techniques are discussed. It is hoped that this will result in an unprecedented multi-disciplinary network of scientific collaboration in CPI to explore much uncharted territory for progress, providing technical inspiration-to the development of the next-generation personal healthcare technology, smart sports-technology, adaptive prosthetics and augmentation of human capability, etc.

Comparison of two sweat test systems for the diagnosis of cystic fibrosis in newborns

OBJECTIVES

In the national newborn screening programme for CF in Switzerland, we compared the performance of two sweat test methods, by investigating the feasibility and diagnostic performance of the Macroduct^® collection method (with chloride mesurement) and Nanoduct^® test (measuring conductivity) for diagnosing CF.

STUDY-DESIGN

We included all newborns with a positive screening result between 2011 and 2015 who were referred to a CF-centre for sweat testing. In the CF-centre, a Macroduct and Nanoduct sweat test were performed simultaneously. If sweat test results were positive or borderline, a DNA analysis was performed. Final diagnosis was based on genetic mutations.

RESULTS

Over 5 years, 445 children were screened positive and in 413 (114 with CF) at least one sweat test was performed (median age at first test, 22 days); both tests were performed in 371 children. A sweat test result was more often available with the Nanoduct compared to the Macroduct (79 vs 60%, P < 0.001). The Nanoduct was equally sensitive as the Macroduct in identifying newborns with CF (sensitivity 98 vs 99%) but less specific (specificity 79 vs 93%; P-value comparing ROC curves = 0.033).

CONCLUSIONS

This national multicentre study revealed high failure rates for Macroduct and Nanoduct in newborns in real life practice. While this needs to be addressed, our results suggested that performing the Nanoduct in addition to the Macroduct might speed up the diagnostic process because it more often yields valid results with comparable diagnostic performance. The addition of the Nanoduct sweat test can therefore help to reduce the stressful time of uncertainty for parents and to start appropriate treatment earlier.

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.

The diagnosis of cystic fibrosis

Establishing the diagnosis of cystic fibrosis (CF) is straight forward in the majority of patients: they present with a clear clinical picture (most frequently chronic respiratory symptoms plus malabsorption), the sweat chloride value is>60mmol/L and two known disease causing CFTR mutations are identified. In less than 5% of subjects, mainly those with a milder or limited phenotype, the diagnostic process is more complex, because initial diagnostic test results are inconclusive: sweat chloride concentration in the intermediate range, less than 2 CF causing mutations identified or both. These patients should be referred to expert centers where bioassays of CFTR function like nasal potential difference measurement or intestinal current measurement can be done. Still, in some patients, despite symptoms compatible with CF and some indication of CFTR dysfunction (e.g. only intermediate sweat chloride value), diagnostic criteria are not met (e.g. only 1 CFTR mutation identified). For these subjects, the term CFTR related disorder (CFTR-RD) is used. Patients with disseminated bronchiectasis, congenital bilateral absence of the vas deferens and acute or recurrent pancreatitis may fall in this category. CF has a very wide disease spectrum and increasingly the diagnosis is being made during adult life, mainly in subjects with milder phenotypes. In many countries, nationwide CF newborn screening (NBS) has been introduced. In screen positive babies, the diagnosis of CF must be confirmed by a sweat test demonstrating a sweat chloride concentration above 60mmol/L. To achieve the benefit of NBS, every baby in whom the diagnosis of CF is confirmed must receive immediate follow-up and treatment in a CF reference center. CF NBS is not full proof: some diagnoses will be missed and in some babies the diagnosis cannot be confirmed nor ruled out with certainty. Screening algorithms that include gene sequencing will detect a high number of such babies that are screen positive with an inconclusive diagnosis (CFSPID). Even in 2016, the most reliable and widely available diagnostic test for CF is the measurement of chloride concentration in sweat. The method of choice is sweat induction by pilocarpine iontophoresis, followed by sweat collection on a gauze or filter paper or in a Macroduct coil. Since mutation specific therapies have become available, it is important to identify the mutations responsible for CF in each individual patient.