Amisha Singapuri

Genome-wide association study to identify genetic determinants of severe asthma

Background The genetic basis for developing asthma has been extensively studied. However, association studies to date have mostly focused on mild to moderate disease and genetic risk factors for severe asthma remain unclear. Objective To identify common genetic variants affecting susceptibility to severe asthma. Methods A genome-wide association study was undertaken in 933 European ancestry individuals with severe asthma based on Global Initiative for Asthma (GINA) criteria 3 or above and 3346 clean controls. After standard quality control measures, the association of 480 889 genotyped single nucleotide polymorphisms (SNPs) was tested. To improve the resolution of the association signals identified, non-genotyped SNPs were imputed in these regions using a dense reference panel of SNP genotypes from the 1000 Genomes Project. Then replication of SNPs of interest was undertaken in a further 231 cases and 1345 controls and a meta-analysis was performed to combine the results across studies. Results An association was confirmed in subjects with severe asthma of loci previously identified for association with mild to moderate asthma. The strongest evidence was seen for the ORMDL3/GSDMB locus on chromosome 17q12-21 (rs4794820, p=1.03×10(−8) following meta-analysis) meeting genome-wide significance. Strong evidence was also found for the IL1RL1/IL18R1 locus on 2q12 (rs9807989, p=5.59×10(−8) following meta-analysis) just below this threshold. No novel loci for susceptibility to severe asthma met strict criteria for genome-wide significance. Conclusions The largest genome-wide association study of severe asthma to date was carried out and strong evidence found for the association of two previously identified asthma susceptibility loci in patients with severe disease. A number of novel regions with suggestive evidence were also identified warranting further study.

Elevated Sputum Interleukin-5 and Submucosal Eosinophilia in Obese Individuals with Severe Asthma

RATIONALE The relationship between airway inflammation and obesity in severe asthma is poorly understood. OBJECTIVES We sought to determine the relationship between sputum mediator profiles and the distribution of eosinophilic inflammation and obesity in people with severe asthma. METHODS Clinical parameters and eight mediators in sputum were assessed in 131 subjects with severe asthma from a single center categorized into lean, overweight, and obese groups defined by their body mass index. In an independent group of people with severe asthma (n = 45) and healthy control subjects (n = 19) eosinophilic inflammation was enumerated in bronchial submucosa, blood, and sputum and related to their body mass index. MEASUREMENTS AND MAIN RESULTS Sputum IL-5 geometric mean (95% confidence interval) (pg/ml) was elevated in the obese (1.8 [1.2-2.6]) compared with overweight (1.1 [0.8-1.3]; P = 0.025) and lean (0.9 [0.6-1.2]; P = 0.018) subjects with asthma and was correlated with body mass index (r = 0.29; P < 0.001). There was no relationship among body mass index, the sputum cell count, or other sputum mediators. In the bronchoscopy group the submucosal eosinophil number in the subjects with asthma was correlated with body mass index (Spearman rank correlation, rs = 0.38; P = 0.013) and the median (interquartile range) number of submucosal eosinophils was increased in obese (19.4 [11.8-31.2]) (cells per square millimeter) versus lean subjects (8.2 [5.4-14.6]) (P = 0.006). There was no significant association between sputum or peripheral blood eosinophil counts and body mass index. CONCLUSIONS Sputum IL-5 and submucosal eosinophils, but not sputum eosinophils, are elevated in obese people with severe asthma. Whether specific antieosinophilic therapy is beneficial, or improved diet and lifestyle in obese asthma has antiinflammatory effects beyond weight reduction, requires further study.

Fevipiprant, a prostaglandin D2 receptor 2 antagonist, in patients with persistent eosinophilic asthma: a single-centre, randomised, double-blind, parallel-group, placebo-controlled trial

BACKGROUND Eosinophilic airway inflammation is often present in asthma, and reduction of such inflammation results in improved clinical outcomes. We hypothesised that fevipiprant (QAW039), an antagonist of prostaglandin D2 receptor 2, might reduce eosinophilic airway inflammation in patients with moderate-to-severe eosinophilic asthma. METHODS We performed a single-centre, randomised, double-blind, parallel-group, placebo-controlled trial at Glenfield Hospital (Leicester, UK). We recruited patients with persistent, moderate-to-severe asthma and an elevated sputum eosinophil count (≥2%). After a 2-week single-blind placebo run-in period, patients were randomly assigned (1:1) by the trial pharmacist, using previously generated treatment allocation cards, to receive fevipiprant (225 mg twice per day orally) or placebo, stratified by the use of oral corticosteroid treatment and bronchoscopy. The 12-week treatment period was followed by a 6-week single-blind placebo washout period. The primary outcome was the change in sputum eosinophil percentage from baseline to 12 weeks after treatment, analysed in the intention-to-treat population. All patients who received at least one dose of study drug were included in the safety analyses. This trial is registered with ClinicalTrials.gov, number NCT01545726, and with EudraCT, number 2011-004966-13. FINDINGS Between Feb 10, 2012, and Jan 30, 2013, 61 patients were randomly assigned to receive fevipiprant (n=30) or placebo (n=31). Three patients in the fevipiprant group and four patients in the placebo group withdrew because of asthma exacerbations. Two patients in the fevipiprant group were incorrectly given placebo (one at the mid-treatment visit and one throughout the course of the study). They were both included in the fevipiprant group for the primary analysis, but the patient who was incorrectly given placebo throughout was included in the placebo group for the safety analyses. Between baseline and 12 weeks after treatment, sputum eosinophil percentage decreased from a geometric mean of 5·4% (95% CI 3·1-9·6) to 1·1% (0·7-1·9) in the fevipiprant group and from 4·6% (2·5-8·7) to 3·9% (CI 2·3-6·7) in the placebo group. Compared with baseline, mean sputum eosinophil percentage was reduced by 4·5 times in the fevipiprant group and by 1·3 times in the placebo group (difference between groups 3·5 times, 95% CI 1·7-7·0; p=0·0014). Fevipiprant had a favourable safety profile, with no deaths or serious adverse events reported. No patient withdrawals were judged by the investigator to be related to the study drug. INTERPRETATION Fevipiprant reduces eosinophilic airway inflammation and is well tolerated in patients with persistent moderate-to-severe asthma and raised sputum eosinophil counts despite inhaled corticosteroid treatment. FUNDING Novartis Pharmaceuticals, AirPROM project, and the UK National Institute for Health Research.

The utility of the mannitol challenge in the assessment of chronic cough: a pilot study

There is a need for more objective outcome measures for chronic cough. In this pilot study we sought to investigate the utility of the mannitol challenge as a cough-provocation test in non-asthmatic chronic cough. We studied 16 healthy controls and 13 subjects with chronic cough. We assessed cough severity using a visual analogue score, capsaicin cough sensitivity, health status using the Leicester Cough Questionnaire and the dose of mannitol to cause 2 (C2) or 5 (C5) coughs. In all of the subjects with chronic cough and 6 of the controls we assessed the 1-week repeatability of the mannitol challenge. We found that in those subjects with chronic cough the geometric mean (logSEM) mannitol C2 and C5 was heightened compared to controls (C2: 4 (0.2) versus 16 (0.1); p = 0.04 and C5: 63 (0.1) versus 251 (0.1); p = 0.04). Cough visual analogue score, capsacin-induced cough sensitivity and health status were also altered in chronic cough compared to healthy controls, but in those subjects with chronic cough none of these outcomes was correlated with the mannitol C2 or C5. The repeatability of the mannitol challenge assessed by intraclass correlation was C2 = 0.53 and C5 = 0.59. A cut-off in the dose of mannitol of 62 mg/ml for C2 and 550 mg/ml for C5 had a sensitivity of 69 and 62% and specificity of 69 and 81% respectively to distinguish chronic coughers from healthy controls. In conclusion, the mannitol challenge my have potential as a novel cough challenge test and further work is required to extend our findings and to assess whether it has utility in different causes of chronic cough.

Lung clearance index in adults with non-cystic fibrosis bronchiectasis

BackgroundLung clearance index (LCI) is a measure of abnormal ventilation distribution derived from the multiple breath inert gas washout (MBW) technique. We aimed to determine the clinical utility of LCI in non-CF bronchiectasis, and to assess two novel MBW parameters that distinguish between increases in LCI due to specific ventilation inequality (LCIvent) and increased respiratory dead space (LCIds).MethodsForty-three patients with non-CF bronchiectasis and 18 healthy control subjects underwent MBW using the sulphur hexafluoride wash-in technique, and data from 40 adults with CF were re-analysed. LCIvent and LCIds were calculated using a theoretical two-compartment lung model, and represent the proportional increase in LCI above its ideal value due to specific ventilation inequality and increased respiratory dead space, respectively.ResultsLCI was significantly raised in patients with non-CF bronchiectasis compared to healthy controls (9.99 versus 7.28, p < 0.01), and discriminated well between these two groups (area under receiver operating curve = 0.90, versus 0.83 for forced expiratory volume in one second [% predicted]). LCI, LCIvent and LCIds were repeatable (intraclass correlation coefficient > 0.75), and correlated significantly with measures of spirometric airflow obstruction.ConclusionLCI is repeatable, discriminatory, and is associated with spirometric airflow obstruction in patients with non-CF bronchiectasis. LCIvent and LCIds are a practical and repeatable alternative to phase III slope analysis and may allow a further level of mechanistic information to be extracted from the MBW test in patients with severe ventilation heterogeneity.

Clinical significance of small airway obstruction markers in patients with asthma.

The role of small airway obstruction in the clinical expression of asthma is incompletely understood.

Validation of a photoacoustic gas analyser for the measurement of functional residual capacity using multiple-breath inert gas washout.

Background: The respiratory mass spectrometer is the current gold-standard technique for performing multiple-breath inert gas washout (MBW), but is expensive and lacks portability. A number of alternative techniques have recently been described. Objectives: We aimed to validate, using an in vitro lung model, an open-circuit MBW system that utilises a portable photoacoustic gas analyser, with sulphur hexafluoride (SF6) as the inert tracer gas. Methods: An acrylic glass lung model was utilised to assess the accuracy of functional residual capacity (FRC) measurements derived from MBW. Measurements were performed in triplicate at 20 combinations of simulated FRC, tidal volume and respiratory rate. FRC measured using MBW (FRCmbw) was compared to FRC calculated from the known dimensions of the model (FRCcalc). MBW was also performed in 10 healthy subjects and 14 patients with asthma. Results: The MBW system measured FRC with high precision. The mean bias of FRCmbw with respect to FRCcalc was -0.4% (95% limits of agreement of -4.6 and 3.9%). The mean coefficient of variation of triplicate FRC measurements was 4.0% in vivo and 1.0% in vitro. MBW slightly underestimated low lung volumes and overestimated high lung volumes, but this did not cause a significant error in lung clearance index except at lung volumes below 1,500 ml. Conclusions: The open-circuit MBW system utilising SF6 as the inert tracer gas and a photoacoustic gas analyser is both accurate and repeatable within the adult range of lung volumes. Further modifications would be required before its use in young children or infants.

Sputum mediator profiling and relationship to airway wall geometry imaging in severe asthma

BackgroundSevere asthma is a heterogeneous disease and the relationship between airway inflammation and airway remodelling is poorly understood. We sought to define sputum mediator profiles in severe asthmatics categorised by CT-determined airway geometry and sputum differential cell counts.MethodsIn a single centre cross-sectional observational study we recruited 59 subjects with severe asthma that underwent sputum induction and thoracic CT. Quantitative CT analysis of the apical segment of the right upper lobe (RB1) was performed. Forty-one mediators in sputum samples were measured of which 21 mediators that were assessable in >50% of samples were included in the analyses.ResultsIndependent of airway geometry, sputum MMP9 and IL-1β were elevated in those groups with a high sputum neutrophil count while sputum ICAM was elevated in those subjects with a low sputum neutrophil count. In contrast, sputum CCL11, IL-1α and fibrinogen were different in groups stratified by both sputum neutrophil count and airway geometry. Sputum CCL11 concentration was elevated in subjects with a low sputum neutrophil count and high luminal and total RB1 area, whereas sputum IL1α was increased in subjects with a high sputum neutrophil count and low total RB1 area. Sputum fibrinogen was elevated in those subjects with RB1 luminal narrowing and in those subjects with neutrophilic inflammation without luminal narrowing.ConclusionsWe have demonstrated that sputum mediator profiling reveals a number of associations with airway geometry. Whether these findings reflect important biological phenotypes that might inform stratified medicine approaches requires further investigation.

Between-visit variability of small airway obstruction markers in patients with asthma

To the Editor: Clinical trials in patients with airway diseases often use forced expiratory volume in 1 s (FEV1) as the sole physiological outcome measure. However, FEV1 is thought to be insensitive to obstruction of the smaller airways, which may be particularly relevant in asthma [1]. Putative markers of small airway obstruction include measures of airway resistance using impulse oscillometry (IOS) [2] and indices of ventilation heterogeneity derived from multiple-breath inert gas washout (MBW) [3]. We recently showed that increased airway resistance at 5 Hz ( R 5) and 20 Hz ( R 20) is associated with worse asthma control and more frequent exacerbations [4], and Farah et al. [5] demonstrated that MBW parameters may be responsive to asthma therapy. In order to conduct clinical trials using these alternative outcome measures, it is necessary to be assured of their repeatability and stability over time. Moreover, an estimate of between-visit variability in the stable state is required so that sample size calculations can be performed. We therefore aimed to determine the between-visit variability of a range of IOS and MBW indices in a group of patients with asthma in the stable state. We investigated between-visit variability over two time intervals, namely 2 weeks and 3 months, in order to encompass the typical lengths of treatment period that are used in clinical trials. We recruited 18 adults (age >18 years) with moderate-to-severe asthma (Global Initiative for Asthma treatment steps 3–5 [6]), diagnosed by a specialist asthma physician in a secondary care setting, according to British Thoracic Society guidelines [ …

Mannitol and AMP do not induce bronchoconstriction in eosinophilic bronchitis: Further evidence for dissociation between airway inflammation and bronchial hyperresponsiveness

Background and objective:  Eosinophilic bronchitis (EB) shares many pathological features with asthma. However, patients with EB do not develop the characteristic physiological abnormalities of asthma: variable airflow obstruction and bronchial hyperresponsiveness (BHR) to a direct bronchial challenge with methacholine. Indirect bronchial challenges with AMP and mannitol are dependent on the presence of airway inflammation, and positive in 10% of asthmatic subjects who have a negative response to methacholine. We have therefore investigated whether subjects with EB are responsive to indirect airway challenge with AMP and mannitol.