Introduction: Bronchial thermoplasty (BT) is a treatment available for severe asthma, but its exact working mechanism and responder profile remains largely unclear. Comprehensive analysis of exhaled volatile organic compounds (VOCs) by gas chromatography-mass spectrometry (GC-MS), a measure for non-invasive monitoring of chronic airway diseases, might identify responders. Aim: To compare exhaled VOCs of responders and non-responders to BT by GC-MS. Methods: Samples of breath from severe asthma patients were collected at baseline on thermal desorption tubes and analysed by GC-MS. Statistical tests on the resulting dataset consisted of: 1) Selection of univariate GC-MS fragments by Mann-Whitney analysis (p<0.05) plus computation of area under the receiver operating characteristics curve (AUROCC>=0.7), 2) Multivariate Principal Component Analysis (PCA), 3) Merging of Principal Components 1 & 2 and extraction of discriminant score (DS) via Linear Discriminant Analysis (LDA), 4) Evaluation of DS via AUROCC calculation. Results: Complete data were available for 14 patients (6 non-responder, 8 responders, based on asthma control questionnaires), [mean(± SD); age 57(±27) years, 27% male, Pre-BD FEV1% 82.1(±36)]. 17 out of 528 GC-MS fragments endured univariate testing and were combined during the multivariate modelling steps. Diagnostic accuracy testing of the extracted DS resulted in an AUROCC of 0.83 (95%CI: 0.59-1.00). Conclusion: This explorative analysis revealed distinctive patterns of exhaled VOCs in responders and non-responders to BT with high diagnostic accuracy for BT response. Implication: Identification of GC-MS revealed patterns which might contribute to unravelling the mechanism of action and patient seletion for BT.
Asthma is an inflammatory disease, causing thickening of the Airway Smooth Muscle (ASM). No current method exists to directly measure ASM within a living patient. Endoscopic Polarization Sensitive Optical Coherence Tomography (PS-OCT) might enable quantification of ASM mass in vivo, by assessing tissue birefringence. We performed in vivo PS-OCT on severe asthma patients and healthy volunteers, with an in-house built distal scanning catheter (1.35 mm), to circumferentially scan the airways at 52 fps B-scan rate. We provided the first comparison of in vivo PS-OCT images between asthma and healthy subjects and demonstrated the ability of PS-OCT to assess ASM content.
Introduction: Bronchial thermoplasty (BT) is an endoscopic treatment for severe asthma that reduces airway smooth muscle (ASM) by radiofrequent energy. No diagnostic method is currently available to assess ASM, other than invasive, focal airway biopsies. Bronchoscopic standard optical coherence tomography (OCT) generates high resolution images of the airways. Polarization sensitive OCT (PS-OCT) provides tissue-specific contrast that might enable ASM detection and quantification. Aim: Use novel PS-OCT to detect ASM and determine changes in ASM before and after BT in severe asthma. Methods: Bronchoscopic PS-OCT was performed from distal to proximal airways in a severe asthma patient before and after BT. Standard OCT high resolution airway wall layer imaging was combined with PS-OCT birefringence and optical axis determination to detect, segment and quantify ASM as compared to histology (gold standard). Results: Standard OCT enabled airway wall layer detection. PS-OCT enables segmentation and quantification of ASM in volumetric airway segments over 5 cm. Circular structure of ASM within the airway was seen. Comparing before and after BT a reduction in ASM mass was detected in line with ASM reduction detected in airway biopsies. Conclusion: Bronchoscopic (PS-)OCT is a promising minimally-invasive imaging technique to assess airway wall layer and ASM mass in severe asthma patients.
Randomised controlled trials (RCT) are the gold standard to provide unbiased data. However, randomly allocating patients to treatments that do not accord with their preferences may influence participation and outcomes. As, in trials comparing treatments of significant different nature (e.g. surgery vs. medication), eligible patients could decline participation due to preference. This could limit the generalizability of results (reduced external validity). Furthermore, trials comparing experimental vs. standard treatment, are likely to include patients preferring experimental treatment, as trial participation is not needed for patients preferring standard treatment. Randomisation to the (non)-preferred strategy could influence adherence to treatment protocol or influence subjective outcomes (reduce internal validity). To preclude the influence of patients’ preference on validity, a patient preference trial (PPT) has been designed. Patients with a preference for a treatment strategies will be treated accordingly, whereas only those patients without a distinct preference will be randomised in the usual way. The aim of this study was to assess the influence of patients’ preference in RCTs. In this systematic review and meta-analyses, we searched for PPTs published between January 1, 2005 and October 5, 2018. PPTs reporting on allocation of patients to random- and preference cohorts, while using the same study protocol for both cohorts were included. The main outcomes were external validity (participation and baseline characteristics) and internal validity (lost to follow-up, cross-over and the primary outcome), assessed by comparing standardised effect sizes of the random- and preference cohorts. In total 117 of 3734 identified articles met screening criteria and 44 were eligible (24873 patients). The participation rate in PPTs was >95% in 14 trials (range 48–100%) and acceptance of randomisation was < 50% in 26 trials (range’s–81%). Higher education, female, older age, race and prior experience with one treatment-arm were characteristics of patients declining randomisation. Lost to follow-up and cross-over rate were significantly higher in the randomised cohort in comparison with the preference cohort. Following a meta-analysis the primary outcomes were comparable, mean difference 0·093(95% CI −0·178;0·364, p = 0·502). Patients’ preference led to a substantial proportion of a specific patient group refusing randomisation, while it did not influence the primary outcome within a PPT. Therefore, in the era of patients becoming more active participants in research, PPTs could increase participation without compromising the validity of the outcomes compared with RCTs.
Objective Randomised controlled trials (RCT) are the gold standard to provide unbiased data. However, when patients have a treatment preference, randomisation may influence participation and outcomes (eg, external and internal validity). The aim of this study was to assess the influence of patients’ preference in RCTs by analysing partially randomised patient preference trials (RPPT); an RCT and preference cohort combined. Design Systematic review and meta-analyses. Data sources MEDLINE, Embase, PsycINFO and the Cochrane Library. Eligibility criteria for selecting studies RPPTs published between January 2005 and October 2018 reporting on allocation of patients to randomised and preference cohorts were included. Data extraction and synthesis Two independent reviewers extracted data. The main outcomes were the difference in external validity (participation and baseline characteristics) and internal validity (lost to follow-up, crossover and the primary outcome) between the randomised and the preference cohort within each RPPT, compared in a meta-regression using a Wald test. Risk of bias was not assessed, as no quality assessment for RPPTs has yet been developed. Results In total, 117 of 3734 identified articles met screening criteria and 44 were eligible (24 873 patients). The participation rate in RPPTs was >95% in 14 trials (range: 48%–100%) and the randomisation refusal rate was >50% in 26 trials (range: 19%–99%). Higher education, female, older age, race and prior experience with one treatment arm were characteristics of patients declining randomisation. The lost to follow-up and cross-over rate were significantly higher in the randomised cohort compared with the preference cohort. Following the meta-analysis, the reported primary outcomes were comparable between both cohorts of the RPPTs, mean difference 0.093 (95% CI −0.178 to 0.364, p = 0.502). Conclusions Patients’ preference led to a substantial proportion of a specific patient group refusing randomisation, while it did not influence the primary outcome within an RPPT. Therefore, RPPTs could increase external validity without compromising the internal validity compared with RCTs. PROSPERO registration number CRD42019094438.
BackgroundAirway remodeling is a prominent feature of asthma, which involves increased airway smooth muscle mass and altered extracellular matrix composition. Bronchial thermoplasty (BT), a bronchoscopic treatment for severe asthma, targets airway remodeling.ObjectiveWe sought to investigate the effect of BT on extracellular matrix composition and its association with clinical outcomes.MethodsThis is a substudy of the TASMA trial. Thirty patients with severe asthma were BT-treated, of whom 13 patients were treated for 6 months with standard therapy (control group) before BT. Demographic data, clinical data including pulmonary function, and bronchial biopsies were collected. Biopsies at BT-treated and nontreated locations were analyzed by histological and immunohistochemical staining. Associations between histology and clinical outcomes were explored.ResultsSix months after treatment, it was found that the reticular basement membrane thickness was reduced from 7.28 μm to 5.74 μm (21% relative reduction) and the percentage area of tissue positive for collagen increased from 26.3% to 29.8% (13% relative increase). Collagen structure analysis revealed a reduction in the curvature frequency of fibers. The percentage area positive for fibulin-1 and fibronectin increased by 2.5% and 5.9%, respectively (relative increase of 124% and 15%). No changes were found for elastin. The changes in collagen and fibulin-1 negatively associated with changes in FEV1 reversibility.ConclusionsBesides reduction of airway smooth muscle mass, BT has an impact on reticular basement membrane thickness and the extracellular matrix arrangement characterized by an increase in tissue area occupied by collagen with a less dense fiber organization. Both collagen and fibulin-1 are negatively associated with the change in FEV1 reversibility. Airway remodeling is a prominent feature of asthma, which involves increased airway smooth muscle mass and altered extracellular matrix composition. Bronchial thermoplasty (BT), a bronchoscopic treatment for severe asthma, targets airway remodeling. We sought to investigate the effect of BT on extracellular matrix composition and its association with clinical outcomes. This is a substudy of the TASMA trial. Thirty patients with severe asthma were BT-treated, of whom 13 patients were treated for 6 months with standard therapy (control group) before BT. Demographic data, clinical data including pulmonary function, and bronchial biopsies were collected. Biopsies at BT-treated and nontreated locations were analyzed by histological and immunohistochemical staining. Associations between histology and clinical outcomes were explored. Six months after treatment, it was found that the reticular basement membrane thickness was reduced from 7.28 μm to 5.74 μm (21% relative reduction) and the percentage area of tissue positive for collagen increased from 26.3% to 29.8% (13% relative increase). Collagen structure analysis revealed a reduction in the curvature frequency of fibers. The percentage area positive for fibulin-1 and fibronectin increased by 2.5% and 5.9%, respectively (relative increase of 124% and 15%). No changes were found for elastin. The changes in collagen and fibulin-1 negatively associated with changes in FEV1 reversibility. Besides reduction of airway smooth muscle mass, BT has an impact on reticular basement membrane thickness and the extracellular matrix arrangement characterized by an increase in tissue area occupied by collagen with a less dense fiber organization. Both collagen and fibulin-1 are negatively associated with the change in FEV1 reversibility.
Introduction: Bronchoscopic optical coherence tomography (OCT) generates high resolution images of the airways. In recent ex vivo studies we have shown that an OCT high intensity (HI) areas correspond and correlate with extracellular matrix (ECM) components in the airway wall (Carpaij et al. AJRCCM 2020;202(5):762-6). In this study, first we aimed to improve the algorithm to segment and quantify airway wall ECM automatically, and secondly apply this in both healthy and asthmatic airways in vivo. Aim: OCT to identify and quantify ECM content in the airway wall. Methods: Bronchoscopic OCT was performed from distal to proximal airways in 18 severe, 42 mild, asthmatics, and 14 healthy subjects. HI areas of 2665 OCT images reflecting ECM content were automatically detected and quantified. Group comparisons were calculated by one-way ANOVA. Results: Segmented HI OCT areas discriminated between healthy, mild and severe asthmatic airways in the larger airways (P<0,01) but not in the smaller airways (P=0,18). Conclusion: Bronchoscopic OCT allows automatic segmentation and quantification of HI OCT areas reflecting airway ECM. These OCT areas were stepwise more abundant in the more proximal airways of severe asthma patients as compared to mild asthmatics and healthy controls. Implication: OCT is a promising tool for real-time quantitative assessment of airway remodelling in airways diseases and possible treatment assessment.
Asthma is a chronic inflammatory disease characterized by airway remodeling (AR), including thickening of airway smooth muscle (ASM) as a key element of this alteration.1James A.L. Wenzel S. Clinical relevance of airway remodelling in airway diseases.Eur Respir J. 2007; 30: 134-155Crossref PubMed Scopus (247) Google Scholar Patients with severe asthma may benefit from bronchial thermoplasty (BT), an endoscopic treatment that targets structural AR and induces ASM reduction.2Castro M. Rubin A.S. Laviolette M. et al.Effectiveness and safety of bronchial thermoplasty in the treatment of severe asthma: a multicenter, randomized, double-blind, sham-controlled clinical trial.Am J Respir Crit Care Med. 2010; 181: 116-124Crossref PubMed Scopus (545) Google Scholar Assessment of AR is critical to evaluate the impact of BT and might provide a tool for patient selection for BT. Polarization sensitive optical coherence tomography (PS-OCT) imaging has been proposed as a minimally invasive diagnostic method to assess ASM mass as an alternative to focal airway biopsies. Bronchoscopic standard optical coherence tomography (OCT) is an imaging modality that generates high-resolution cross-sectional images of the airways. PS-OCT imaging provides tissue-specific contrast by assessing tissue birefringence, which enables ASM detection and quantification.3Adams D.C. Hariri L.P. Miller A.J. et al.Birefringence microscopy platform for assessing airway smooth muscle structure and function in vivo.Sci Transl Med. 2016; 8: 359ra131Crossref PubMed Scopus (61) Google Scholar The aim of this pilot study is to evaluate in vivo bronchoscopic PS-OCT imaging as a safe and minimally invasive, volumetric imaging technique to visualize and quantify ASM. To our knowledge, this is the first time an ASM reduction after BT was detected by PS-OCT imaging and a correlation between ASM mass in biopsies and in vivo PS-OCT images was found. Moreover, 3-dimensional (3D) volumetric reconstructions of ASM before and after BT are performed. This is a substudy of the TASMA (Unravelling Targets of Therapy in Bronchial Thermoplasty in Severe Asthma) trial,4National Institutes of Health Clinical Center. Unravelling targets of therapy in bronchial thermoplasty in severe asthma (TASMA). NCT02225392. ClinicalTrials.gov. National Institutes of Health; 2014. Updated April 9, 2020. https://clinicaltrials.gov/ct2/show/record/NCT02225392Google Scholar in which patients with severe asthma have been treated with BT, except for the middle lobe.5Goorsenberg A.W.M. d'Hooghe J.N.S. Srikanthan K. et al.Bronchial thermoplasty induced airway smooth muscle reduction and clinical response in severe asthma: the TASMA randomized trial.Am J Respir Crit Care Med. 2021; 203: 175-184Crossref PubMed Scopus (18) Google Scholar In three patients, endobronchial PS-OCT imaging was performed in the right lower lobe (RLL) (four to seven pullbacks) and the untreated middle lobe (two pullbacks) 6 months after BT. One of these patients underwent bronchoscopy including PS-OCT imaging prior to BT treatment in the RLL (four pullbacks). PS-OCT imaging was found to be feasible and safe; no adverse events occurred. PS-OCT system specifications have been previously described.6Feroldi F. Willemse J. Davidoiu V. et al.In vivo multifunctional optical coherence tomography at the periphery of the lungs.Biomed Opt Express. 2019; 10: 3070-3091Crossref PubMed Scopus (14) Google Scholar Volumetric PS-OCT images were acquired by inserting the OCT catheter (1.35 mm diameter) through the working channel of the bronchoscope into the selected airway segment until the alveolar compartment and helical scanning manual pullback was performed. Analysis of 26 PS-OCT pullbacks (650-1,000 frames each) and statistical analysis of the data were done in MATLAB R2018a (MathWorks). To extract the birefringence properties of ASM, we adapted an algorithm developed by Villiger et al.7Villiger M. Lorenser D. McLaughlin R.A. et al.Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour.Sci Rep. 2016; 6: 28771Crossref PubMed Scopus (94) Google Scholar Identification of the sample optic axis (OA), in which orientation is given by muscle fibers aligned in the same direction, provides a robust way of highlighting the presence of ASM.5Goorsenberg A.W.M. d'Hooghe J.N.S. Srikanthan K. et al.Bronchial thermoplasty induced airway smooth muscle reduction and clinical response in severe asthma: the TASMA randomized trial.Am J Respir Crit Care Med. 2021; 203: 175-184Crossref PubMed Scopus (18) Google Scholar To retrieve depth-resolved OA orientation images, the presence of preceding birefringent layers8Willemse J. Gräfe M.G.O. Verbraak F.D. de Boer J.F. In vivo 3D determination of peripapillary scleral and retinal layer architecture using polarization-sensitive optical coherence tomography.Transl Vis Sci Technol. 2020; 9: 21Crossref PubMed Scopus (7) Google Scholar and variation of the incident polarization state induced by the rotation of the catheter motor were addressed. To isolate birefringent structures in OA orientation images, the latter was thresholded with OA uniformity, as a measure of the uniformity of the OA orientation over a small region.6Feroldi F. Willemse J. Davidoiu V. et al.In vivo multifunctional optical coherence tomography at the periphery of the lungs.Biomed Opt Express. 2019; 10: 3070-3091Crossref PubMed Scopus (14) Google Scholar ASM was automatically segmented from other birefringent layers by its consistent orientation throughout the pullback. For each airway segment, we measured the percentage of the ASM area over the total OCT cross section, extending from the outer sheath of the catheter to an imaging depth of 1.4 mm, and its average value along the pullback was calculated. Extremely distal frames imaged the alveolar compartment, where ASM was barely observed, and were not included in the calculations. Frames acquired proximally in the airway for which with the enlarging of the lumen ASM fall beyond the imaging depth of PS-OCT (airway diameter > 3 mm) were excluded. Immediately after PS-OCT imaging, endobronchial biopsies were taken of predefined (sub)segmental airway carinas before and after BT treatment (two to four in the left lower lobe and RLL, and two in the distal and proximal middle lobe). Considering anatomic similarity between the lower lobes, biopsies from the nonimaged left lower lobe were included.9Pretolani M. Dombret M.C. Thabut G. et al.Reduction of airway smooth muscle mass by bronchial thermoplasty in patients with severe asthma.Am J Respir Crit Care Med. 2014; 190: 1452-1454Crossref PubMed Scopus (121) Google Scholar In short, a total of 19 biopsies were paraffin-embedded, sectioned, and stained for ASM-specific desmin (clone-33; BioGenes); sections without epithelium/mucosal layer or with artefacts were excluded from the analysis.10d'Hooghe J.N.S. Goorsenberg A.W.M. Ten Hacken N.H.T. et al.Airway smooth muscle reduction after bronchial thermoplasty in severe asthma correlates with FEV1.Clin Exp Allergy. 2019; 49: 541-544Crossref PubMed Scopus (10) Google Scholar From each biopsy (except two), two sections with the highest surface area were included in the analysis and blindly measured, using automated digital image analysis software (ImageJ; NIH). ASM mass in the biopsies was measured as the percentage of positive stained desmin area compared with the total biopsy area. To investigate whether the PS-OCT-detected ASM content correlated with histology determined-ASM content, linear regression analysis including SEM as weights in both coordinates was implemented.11York D. Evensen N.M. López Martínez M. De Basabe Delgado J. Unified equations for the slope, intercept, and standard errors of the best straight line.Am J Phys. 2004; 72: 368-375Crossref Scopus (621) Google Scholar Correlation of ASM content in multiple biopsies in the RLL and left lower lobe and PS-OCT pullbacks in the RLL was found. Performing a χ2 test (χ2 = 39.90, 5 df), an approximate value of P < .001 was found for the null hypothesis (slope is zero) (Fig 1). The larger SEM of the middle lobe biopsies was attributed to the significant difference of ASM content in distal and proximal biopsies. To further substantiate that PS-OCT imaging is able to visualize and quantify ASM content, we investigated if PS-OCT imaging was able to detect a decrease in ASM content after BT in line with biopsy studies.10d'Hooghe J.N.S. Goorsenberg A.W.M. Ten Hacken N.H.T. et al.Airway smooth muscle reduction after bronchial thermoplasty in severe asthma correlates with FEV1.Clin Exp Allergy. 2019; 49: 541-544Crossref PubMed Scopus (10) Google Scholar A reduction of ASM was found performing an unpaired heteroscedastic t test (pre-BT: n = 4, post-BT: n = 5; P < .05) on PS-OCT measurements acquired in the patients imaged before and after BT. Reduction in ASM was visualized and quantified with PS-OCT images acquired before and after BT in the same airway location (Fig 2). The 3D volumetric reconstruction visualized a reduction of ASM especially in the proximal airway, which corresponds to the area directly treated with BT (Figs 2C, 2D). A decrease of ASM spikes was observed after BT in the proximal airway (Fig 2D). In general, a spiraling distribution of ASM along the airways was observed. The small number of patients imaged is a limitation of this study, but given the relatively high number of airways imaged before and after BT together with the histologic reference standard, we envision this work as a valuable proof of principle study. Future validation of this technique in a larger group of patients is needed. In conclusion, our data show bronchoscopic PS-OCT imaging is a promising minimally invasive 3D imaging technique to assess airway ASM content which might contribute to the assessment of AR in patients with severe asthma. Author contributions: J. T. A., P. I. B., and J. F. B. contributed to the conception and design of the manuscript. M. V., F. F., J. N. S. H., and A. W. M. G. performed data acquisition. M. V., P. C. W., J. W., J. T. A., P. I. B., and J. F. B. contributed to the analysis and interpretation of the data. Drafting of the manuscript was done by M. V. and P. C. W. The manuscript was critically revised for important intellectual content by M. V., P. C. W., J. W., A. W. M. G., F. F., J. N. S. H., J. T. A., P. I. B., and J. F. B. Role of sponsors: The funders were not involved in data collection, analysis, decision to publish, or preparation of the manuscript. Other contributions: We thank Mathisca de Gunst, PhD, and Michael W. T. Tanck, Ir, PhD, for statistical advice. We thank Dirck J. van Iperen for the assistance with the development of the OCT catheter.
Bronchial thermoplasty (BT) is a bronchoscopic treatment for severe asthma. Although multiple trials have demonstrated clinical improvement after BT, optimal patient selection remains a challenge and the mechanism of action is incompletely understood. The aim of this study was to examine whether exhaled breath analysis can contribute to discriminate between BT-responders and non-responders at baseline and to explore pathophysiological insights of BT.
