Ester M.M. Klaassen

Profiling of Volatile Organic Compounds in Exhaled Breath As a Strategy to Find Early Predictive Signatures of Asthma in Children

Wheezing is one of the most common respiratory symptoms in preschool children under six years old. Currently, no tests are available that predict at early stage who will develop asthma and who will be a transient wheezer. Diagnostic tests of asthma are reliable in adults but the same tests are difficult to use in children, because they are invasive and require active cooperation of the patient. A non-invasive alternative is needed for children. Volatile Organic Compounds (VOCs) excreted in breath could yield such non-invasive and patient-friendly diagnostic. The aim of this study was to identify VOCs in the breath of preschool children (inclusion at age 2–4 years) that indicate preclinical asthma. For that purpose we analyzed the total array of exhaled VOCs with Gas Chromatography time of flight Mass Spectrometry of 252 children between 2 and 6 years of age. Breath samples were collected at multiple time points of each child. Each breath-o-gram contained between 300 and 500 VOCs; in total 3256 different compounds were identified across all samples. Using two multivariate methods, Random Forests and dissimilarity Partial Least Squares Discriminant Analysis, we were able to select a set of 17 VOCs which discriminated preschool asthmatic children from transient wheezing children. The correct prediction rate was equal to 80% in an independent test set. These VOCs are related to oxidative stress caused by inflammation in the lungs and consequently lipid peroxidation. In conclusion, we showed that VOCs in the exhaled breath predict the subsequent development of asthma which might guide early treatment.

Elevated inflammatory markers at preschool age precede persistent wheezing at school age

To cite this article: van de Kant KDG, Jansen MA, Klaassen EMM, van der Grinten CP, Rijkers GT, Muris JWM, van Schayck OCP, Jöbsis Q, Dompeling E. Elevated inflammatory markers at preschool age precede persistent wheezing at school age. Pediatr Allergy Immunol 2012: 23: 259–264.

Exhaled biomarkers and gene expression at preschool age improve asthma prediction at 6 years of age.

RATIONALE A reliable asthma diagnosis is difficult in wheezing preschool children. OBJECTIVES To assess whether exhaled biomarkers, expression of inflammation genes, and early lung function measurements can improve a reliable asthma prediction in preschool wheezing children. METHODS Two hundred two preschool recurrent wheezers (aged 2-4 yr) were prospectively followed up until 6 years of age. At 6 years of age, a diagnosis (asthma or transient wheeze) was based on symptoms, lung function, and asthma medication use. The added predictive value (area under the receiver operating characteristic curve [AUC]) of biomarkers to clinical information (assessed with the Asthma Predictive Index [API]) assessed at preschool age in diagnosing asthma at 6 years of age was determined with a validation set. Biomarkers in exhaled breath condensate, exhaled volatile organic compounds (VOCs), gene expression, and airway resistance were measured. MEASUREMENTS AND MAIN RESULTS At 6 years of age, 198 children were diagnosed (76 with asthma, 122 with transient wheeze). Information on exhaled VOCs significantly improved asthma prediction (AUC, 89% [increase of 28%]; positive predictive value [PPV]/negative predictive value [NPV], 82/83%), which persisted in the validation set. Information on gene expression of toll-like receptor 4, catalase, and tumor necrosis factor-α significantly improved asthma prediction (AUC, 75% [increase of 17%]; PPV/NPV, 76/73%). This could not be confirmed after validation. Biomarkers in exhaled breath condensate and airway resistance (pre- and post- bronchodilator) did not improve an asthma prediction. The combined model with VOCs, gene expression, and API had an AUC of 95% (PPV/NPV, 90/89%). CONCLUSIONS Adding information on exhaled VOCs and possibly expression of inflammation genes to the API significantly improves an accurate asthma diagnosis in preschool children. Clinical trial registered with www.clinicaltrial.gov (NCT 00422747).

Exhaled breath profiling in diagnosing wheezy preschool children

Although wheeze is common in preschool children, the underlying pathophysiology has not yet been disentangled. Volatile organic compounds (VOCs) in exhaled breath may serve as noninvasive markers of early wheeze. We aimed to assess the feasibility of VOC collection in preschool children, and to study whether a VOC profile can differentiate between children with and without recurrent wheeze. We included children (mean (range) age 3.3 (1.9–4.5) yrs) with (n=202) and without (n=50) recurrent wheeze. Exhaled VOCs were analysed by gas chromatography–time-of-flight mass spectrometry. VOC profiles were generated by ANOVA simultaneous component analysis (ASCA) and sparse logistic regression (SLR). Exhaled breath collection was possible in 98% of the children. In total, 913 different VOCs were detected. The signal-to-noise ratio improved after correction for age, sex and season using ASCA pre-processing. An SLR model with 28 VOCs correctly classified 83% of the children (84% sensitivity, 80% specificity). After six-fold cross-validation, 73% were correctly classified (79% sensitivity, 50% specificity). Assessment of VOCs in exhaled breath is feasible in young children. VOC profiles are able to distinguish children with and without recurrent wheeze with a reasonable accuracy. This proof of principle paves the way for additional research on VOCs in preschool wheezing.

A systematic review of CD14 and toll-like receptors in relation to asthma in Caucasian children

The aetiology of childhood asthma is complex. An early dysfunction in the immunological development of the innate immune system in combination with environmental factors possibly triggers asthma. CD14 and toll-like receptors are important components of the innate immune system. The aim of this systematic review was to obtain a better insight into the relation between CD14 and toll-like receptors and childhood asthma in Caucasians. We searched PubMed and EMBASE for relevant articles. In total, 44 articles were included. The quality of the selected studies was independently assessed by the first two authors using the Newcastle-Ottawa quality assessment scale. Toll-like receptor 2, toll-like receptor 6, toll-like receptor 9, and toll-like receptor 10 appear to have some association with childhood asthma in Caucasians. The evidence for a relation of CD14 with childhood asthma is limited. In conclusion, there is no convincing evidence yet for a role of CD14 and toll-like receptors in relation to childhood asthma. Future studies should include haplotype analysis and take environmental factors into account to further clarify the role of CD14 and toll-like receptors on childhood asthma.

Symptoms, but Not a Biomarker Response to Inhaled Corticosteroids, Predict Asthma in Preschool Children with Recurrent Wheeze

Background. A reliable asthma diagnosis is challenging in preschool wheezing children. As inhaled corticosteroids (ICS) are more effective in asthmatics than in children with transient wheeze, an ICS response might be helpful in early asthma diagnosis. Methods. 175 children (aged two–four years) with recurrent wheeze received 200 μg Beclomethasone extra-fine daily for eight weeks. Changes in Exhaled Breath Condensate (EBC) biomarkers (pH, interleukin (IL)-1α, IL-2, IL-4, IL-5, IL-10, IFN-γ, sICAM, and CCL-11), Fractional exhaled Nitric Oxide (FeNO), airway resistance, and symptoms were assessed. At six years of age a child was diagnosed as transient wheezer or asthmatic. Adjusted logistic regression analysis was performed with multiple testing correction. Results. 106 transient wheezers and 64 asthmatics were analysed at six years of age. Neither changes in EBC biomarkers, nor FeNO, airway resistance, or symptoms during ICS trial at preschool age were related to asthma diagnosis at six years of age. However, asthmatics had more airway symptoms before the start of the ICS trial than transient wheezers (P < 0.01). Discussion. Although symptom score in preschool wheezing children at baseline was associated with asthma at six years of age, EBC biomarkers, airway resistance, or symptom response to ICS at preschool age could not predict asthma diagnosis at six years of age.

Can exhaled inflammatory markers predict a steroid response in wheezing preschool children

Background The efficacy of inhaled corticosteroids (ICS) varies among wheezing preschool children. Currently, it is not possible to predict which fraction of wheezing children will benefit from an ICS treatment.

Integrative genomic analysis identifies a role for intercellular adhesion molecule 1 in childhood asthma

Childhood asthma is characterized by chronic airway inflammation. Integrative genomic analysis of airway inflammation on genetic and protein level may help to unravel mechanisms of childhood asthma. We aimed to employ an integrative genomic approach investigating inflammation markers on DNA, mRNA, and protein level at preschool age in relationship to asthma development.

An ADAM33 Polymorphism Associates with Progression of Preschool Wheeze into Childhood Asthma : A Prospective Case-Control Study with Replication in a Birth Cohort Study

Background The influence of asthma candidate genes on the development from wheeze to asthma in young children still needs to be defined. Objective To link genetic variants in asthma candidate genes to progression of wheeze to persistent wheeze into childhood asthma. Materials and Methods In a prospective study, children with recurrent wheeze from the ADEM (Asthma DEtection and Monitoring) study were followed until the age of six. At that age a classification (transient wheeze or asthma) was based on symptoms, lung function and medication use. In 198 children the relationship between this classification and 30 polymorphisms in 16 asthma candidate genes was assessed by logistic regression. In case of an association based on a p<0.10, replication analysis was performed in an independent birth cohort study (KOALA study, n = 248 included for the present analysis). Results In the ADEM study, the minor alleles of ADAM33 rs511898 and rs528557 and the ORMDL3/GSDMB rs7216389 polymorphisms were negatively associated, whereas the minor alleles of IL4 rs2243250 and rs2070874 polymorphisms were positively associated with childhood asthma. When replicated in the KOALA study, ADAM33 rs528557 showed a negative association of the CG/GG-genotype with progression of recurrent wheeze into childhood asthma (0.50 (0.26-0.97) p = 0.04) and no association with preschool wheeze. Conclusion Polymorphisms in ADAM33, ORMDL3/GSDMB and IL4 were associated with childhood asthma in a group of children with recurrent wheeze. The replication of the negative association of the CG/GG-genotype of rs528557 ADAM33 with childhood asthma in an independent birth cohort study confirms that a compromised ADAM33 gene may be implicated in the progression of wheeze into childhood asthma.

CD14/Toll-like receptors interact with bacteria and regulatory T-cells in the development of childhood asthma

To the Editor: The susceptibility to asthma development in childhood is influenced by genetic as well as environmental factors, and interactions between these factors [1–3]. However, at present, their exact role is still largely undetermined. Genetic variations in the innate immune system may lead to different adaptive immune responses to bacteria and may therefore vary the development of asthma [2, 4, 5]. We performed a prospective longitudinal study in preschool children, in which we determined polymorphisms in Toll-like receptors ( TLR s) and CD14 , the presence of bacteria, and the proportion of regulatory T-cells (Treg) all in relation to an asthma diagnosis at 6 years of age. We hypothesise that specific genetic variants in genes that affect the innate immune system influence the response to bacteria and the recruitment of Treg in preschool children, leading to an increased likelihood of asthma at 6 years of age. The Asthma DEtection and Monitoring (ADEM) study is a long-term prospective case–control study. A detailed protocol of this study has previously been published [6]. A total of 202 children who had experienced at least two wheezing episodes during their lifetime (International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire) [7] and 50 children without wheezing episodes were included at 2–4 years of age. The children were randomly selected from a random population sample in Limburg, the Netherlands, based on the presence or absence of recurrent wheeze [6]. During the initial visit, saliva or buccal cells (DNA), nasal and throat swabs (bacterial cultures), and blood (Treg) were collected. Participants were genotyped for six single nucleotide polymorphisms in TLR2 , TLR4 , TLR9 and CD14 (Sequenom …