Importance of concomitant local and systemic eosinophilia in uncontrolled asthma

Systemic and airway eosinophilia are recognised features of asthma. There are, however, patients who exhibit discordance between local and systemic eosinophilia. In this study, we sought to determine the prevalence and characteristics of patients with concordant and discordant systemic and bronchial eosinophilia. We conducted a retrospective study on 508 asthmatics with successful sputum induction. We assessed the relationship between blood and sputum eosinophils by breaking down the population into four groups according to blood (o400 cells per mm) and sputum (o3%) eosinophils. Then, we prospectively reassessed the link between eosinophils and asthma control (Asthma Control Questionnaire (ACQ)) and exacerbation rate in a new cohort of 250 matched asthmatics. In our retrospective cohort, asthmatics without eosinophilic inflammation were the largest group (49%). The group with isolated sputum eosinophilia (25%) was, compared with noneosinophilic asthma, associated with lower forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity ratio and higher bronchial hyperresponsiveness and exhaled nitric oxide fraction (FeNO). Asthmatics exhibiting isolated systemic eosinophilia (7%) had similar characteristics as noneosinophilic asthmatics. The group with concordant systemic and airway eosinophilia (19%) showed remarkable male predominance, and had the lowest airway calibre, ACQ score and quality of life, and the highest bronchial hyperresponsiveness, FeNO and exacerbation rate. The prospective cohort confirmed the different subgroup proportions and the higher ACQ and exacerbation rates in cases of diffuse eosinophilia compared with noneosinophilic asthmatics. Concomitant systemic and bronchial eosinophilic inflammation contribute to poor asthma control. @ERSpublications Concomitant systemic and bronchial eosinophilic inflammation contributes to poor asthma control http://ow.ly/sLtYr This article has supplementary material available from www.erj.ersjournals.com Received: Nov 18 2013 | Accepted after revision: Dec 27 2013 Support statement: The study was supported by IAP (Interuniversity Attraction Poles) Project P6/35, and unrestricted research grants from Chiesi, GSK and AstraZeneca. Conflict of interest: None declared. Copyright ERS 2014 ORIGINAL ARTICLE IN PRESS | CORRECTED PROOF Eur Respir J 2014; in press | DOI: 10.1183/09031936.00201813 1 . Published on February 13, 2014 as doi: 10.1183/09031936.00201813 ERJ Express Copyright 2014 by the European Respiratory Society. Introduction Bronchial asthma is a complex airway inflammatory disease. The eosinophilic feature is recognised as a pivotal trait of the disease [1]. The technique of induced sputum has been instrumental in assessing the proportion of eosinophilic asthma. It is now accepted that eosinophilic asthma, defined as a sputum eosinophil count of 2–3% or higher, represents slightly less than half of the asthmatic population [2–5]. In asthma, sputum eosinophil count correlates with blood eosinophil count [4, 6–8] and blood eosinophil count is considered as a good surrogate marker for sputum eosinophil count (over 2–3% with a cut-off of 220 cells per mm or 3%) [4, 9]. However, the sensitivity and specificity of blood eosinophils to predict a sputum eosinophil proportion of o3% are ,80%, and there are patients who show discordance between local and systemic inflammation. There is a huge controversy about the role of eosinophils as a key player in asthma severity [10–21]. Some studies have looked at airway eosinophils in bronchoalveolar lavage (BAL) [21], induced sputum [11, 12, 14, 16–18] and bronchial biopsies [19, 20], while others focused on systemic inflammation through blood eosinophil count measurement [20]. Discrepancies between studies may be linked to the different compartments sampled and, for some of the studies, to the limited number of subjects investigated. While inhaled corticoids, the recommended mainstay treatment of asthma, have been consistently shown to reduce airway eosinophilic inflammation and improve asthma control [22], their effect on systemic eosinophilia was shown to be rather weak at usual doses [23]. By contrast, the new biologicals directed towards interleukin-5 were shown to dramatically decrease circulating blood eosinophils, an effect that was associated with the reduction of asthma exacerbation [24] and improvement in asthma control [25]. To the best of our knowledge, there has never been detailed investigation of the relationship between blood and sputum eosinophil in a large population of asthmatics. In this study, we sought to determine whether looking at blood and sputum eosinophilic inflammation might help in our understanding of asthma severity. We first retrospectively investigated the demographic, functional and symptomatic features of 508 asthmatics classified according to systemic and local eosinophilic inflammation, and then prospectively validated the relationship between asthma control and eosinophilic inflammation in a new cohort of 250 patients well matched to our retrospective cohort with respect to demographic, functional and treatment characteristics. Material and methods Subject characteristics We conducted a retrospective study on a series of 508 patients with asthma recruited from the University Asthma Clinic of Liege, Liege, Belgium, between October 1, 2005 and June 27, 2011. The patients came from routine practice to University Hospital, Liege, and were recruited by two clinicians involved in asthma. Entry criteria were any patients with asthma aged o18 years who agreed to undergo detailed investigation at the asthma clinic. The visits were not parts of an asthma trial. All the patients who had a successful sputum induction were included in the study. Their demographic and functional characteristics are summarised in tables 1 and 2. Asthma was diagnosed based on the presence of chronic respiratory symptoms such as cough, breathlessness or dyspnoea together with the demonstration of airflow variability. The latter was defined by airway hyperresponsiveness shown by one or more of the following: increase in forced expiratory volume in 1 s (FEV1) of .12% and 200 mL following inhalation of 400 mg salbutamol; or inhaled concentration of methacholine provoking a 20% fall in FEV1 of ,16 mg?mL. Methacholine challenge was performed according to a standardised methodology as previously described [26]. Subjects were characterised as atopic if they had at least one positive specific IgE test (.0.35 kU?L; Phadia, Groot-Bijgaarden, Belgium) for at least one common aeroallergen (cat, dog, house dust mites, grass pollen, tree pollen and a mixture of moulds). Exacerbation in the previous year was defined by a course of oral corticoids for o3 days for a case of asthma worsening. Nasal polyps and sinusitis was diagnosed by an ear, nose and throat physician either by endoscopy or sinus computed tomography. Gastro-oesophageal reflux was diagnosed either by symptoms of pyrosis at history taking or the presence of oesophagitis demonstrated by gastroscopy. Study design Patients underwent exhaled nitric oxide fraction (FeNO) measurement at a flow rate of 50 mL?s according to the European Respiratory Society (ERS)/American Thoracic Society (ATS) recommendations (NIOX; Aerocrine, Solna, Sweden). FeNO was first measured and followed by spirometry with bronchodilation, sputum induction and blood sampling. All tests were performed on the same day. ASTHMA | F.N. SCHLEICH ET AL. DOI: 10.1183/09031936.00201813 2 Quality of life was assessed using the self-administered Asthma Quality of Life Questionnaire [27] and asthma control by the Asthma Control Questionnaire (ACQ) of JUNIPER et al. [28]. Sputum was induced and processed as previously reported [29], and was successful in 78% of the patients encountered in our asthma clinic, which is similar to previous reports [30, 31]. Cell count were estimated on samples centrifuged (cytospin) and stained with Diff-Quick after counting 500 cells (Dade, Brussels, Belgium). Prospective study validation To validate the results of the retrospective analysis of the link between asthma control and eosinophilic inflammation, we conducted a prospective study. A new cohort of 250 consecutive patients was recruited from routine practice between June 30, 2011 and January 12, 2013. None of these patients had been included in the retrospective cohort. Their demographic, functional and treatment characteristics were similar to the retrospective population (tables 1 and 2). Exacerbation rate for the prospective population was measured through a telephone call over a period of 12 months following the visit to the asthma clinic, during which treatment was initiated or adjusted according to asthma control, lung function and inflammatory markers at the discretion of the clinician. 13 patients were lost to follow-up and in the 17 patients in whom the observation period was ,1 year, we calculated the annualised exacerbation rate. This study was conducted with the approval of the ethics committee of CHU Liege. TABLE 1 Demographic, control and treatment characteristics for the whole population Characteristics Retrospective cohort Prospective cohort Subjects n 508 250 Males/females n 201/307 99/151 Age years 52 (19–88) 50 (16–85) Age of onset ,12 years 24 22 12–40 years 37 36 o40 years 39 42 Height cm 167¡9 168¡9 Weight kg 74¡16 73¡17 Atopy yes/no (%) 296/212 (58) 148/102 (59) Current smokers 101 (20) 55 (22) Exposure pack-years 22 (0.5–60) 25 (2–60) Ex-smokers 99 (19) 38 (15) Exposure pack-years 15 (0.5–90) 17 (0.5–63) Bronchiectasis 19 17 Gastro-oesophageal reflux 79 71* Nasal polyposis 22 27 Sinusitis 42 41 Rhinitis 58 56 Exacerbations per patient per year 0.68¡1.50 0.86¡2.02 LABA 319 (63) 141 (56) LTRA 93 (18) 50 (20) Theophylline 16 (3) 11 (4) ICS Steroid naı̈ve 153 (30) 82 (33) Low dose 73 (14) 35 (14) Moderate dose 138 (27) 63 (25) High dose 144 (28) 70 (28) Oral corticosteroids 32 (6) 25 (10) Data are presented as median (range), %, mean¡SD or n (%), unless otherwise stated. Exacerbations were evaluated during the year prior to the visit. LABA: long-acting b2-agonist; LTRA: leukotriene receptor antagonist; ICS: Inhaled corticosteroids. High dose: .1000 mg?day beclomethasone. : during the year prior to the visit; : f500 mg per day beclomethasone; : 500–1000mg per day beclomethasone; : .1000 mg per day beclomethasone; : n5174; : n5273; : n5428; : n5237. *: p,0.05. ASTHMA | F.N. SCHLEICH ET AL. DOI: 10.1183/09031936.00201813 3 Statistical analyses We used blood eosinophil count and sputum eosinophil percentage to subdivide our asthmatic population into four groups. The chosen blood (o400 cells per mm) and sputum (o3%) threshold values were considered as the limit of abnormality by our routine laboratory. The results were expressed as mean¡SD or mean¡SEM for continuous variables; median (range) was preferred for skewed distributions. For categorical variables, the number of observations and percentages are given in each category. Comparisons between different subgroups were performed with a Kruskal–Wallis test. The Spearman correlation coefficient was used to measure the association between clinical parameters. Power calculations indicated a required total sample size of 250 subjects to confirm a change in ACQ score o0.5 between noneosinophilic asthmatics and patients exhibiting diffuse eosinophilic inflammation, with a power of 80%. The results were considered to be significant at the 5% critical level (p,0.05). Results The demographic, functional and inflammatory characteristics of the retrospective cohort of asthmatics (n5508), classified according to their blood (threshold 400 cells per mm) [25] and sputum eosinophil counts (threshold 3%), are described in tables 3–5. The patients without evidence of eosinophilic inflammation represented the largest group, accounting for 49% of the cohort. Those patients with selective airway eosinophilic inflammation came second, accounting for 25% of the patients, whereas those exhibiting the reverse picture were much less numerous, only representing 7%. Patients combining systemic and airway eosinophilic inflammation account for 19% of the patients. The inhaled corticoids treatment regimen was similar between subgroups (table 3). Compared with noneosinophilic asthmatics, the characteristics of patients exhibiting isolated sputum eosinophilia were a higher proportion of males and atopic subjects, higher total serum IgE levels, lower FEV1 and FEV1/forced vital capacity ratio, and higher bronchial hyperresponsiveness and reversibility to b2agonists (fig. 1, and tables 4 and 5). As for patients with high levels of blood eosinophils without sputum eosinophilia, they had a higher total serum IgE compared with noneosinophilic asthmatics (fig. 1 and table 5). The presence of both local and systemic eosinophilic inflammation was strikingly more frequent in males, and associated with the greatest lung function impairment, and the lowest asthma control (mean¡SEM ACQ score 2.54¡1.45 versus 1.88¡1.39; mean difference 0.66, 95% CI -0.99– -0.32 (p50.0001)) (figs 1 and 2) and quality of life (table 4). They also had the highest FeNO while those with eosinophilia in only one compartment had similar, intermediate FeNO. Noneosinophilic asthmatics had the lowest FeNO, comparable to that found in healthy subjects (fig. 3 and table 5). Patients with increased sputum eosinophilia reported greater numbers of severe exacerbations in the previous year, and this was particularly the case for those displaying concordant systemic and airway eosinophilia (table 3). Likewise, the proportion of sinusitis and nasal polyps was clearly raised in eosinophilic asthmatics while there was no difference regarding the gastro-oesophageal reflux (table 3). In patients treated with high doses of inhaled corticosteroids (n5144), the proportions of the different subgroups were similar to those found in the whole cohort, and the subgroup exhibiting both bronchial and TABLE 2 Functional and inflammatory characteristics for the whole population Characteristics Retrospective cohort Prospective cohort FEV1 % predicted 84¡19 82¡21 FEV1/FVC % 73¡11 71¡15* PC20 mg?mL geometric mean (range) 3.20 (0.025–16) 2.92 (0.05–16) Reversibility % 11¡14 9¡10 ACQ score 2.01¡1.38 2.00¡1.25 AQLQ score 4.61¡1.35 4.46¡1.39 Blood eosinophil count cells per mm 230 (0–3220) 188 (0–1133)* FeNO ppb 27 (0–247) 25 (4–348) Sputum eosinophils % 2 (0–94) 2.8 (0–90) Sputum neutrophils % 45 (0–100) 49 (0–100) Data are presented as mean¡SD or median (range), unless otherwise stated. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; PC20: provocative concentration of methacholine causing a 20% fall in FEV1; ACQ: Asthma Control Questionnaire; AQLQ: Asthma Quality of Life Questionnaire; FeNO: exhaled nitric oxide fraction. *: p,0.05. ASTHMA | F.N. SCHLEICH ET AL. DOI: 10.1183/09031936.00201813 4 systemic eosinophilic inflammation had the highest exacerbation rate and the poorest lung function (table 6). In order to validate the relationship between poor asthma control and comprehensive eosinophilic inflammation, we prospectively recruited a population of 250 asthmatics whose demographic, functional and inflammatory characteristics were similar to our retrospective cohort (table 1 and 2). In this population, we found similar proportions of patients in the different subgroups (47% were patients without evidence of eosinophilic inflammation, 32% exhibited isolated sputum eosinophilia, 4% had isolated systemic eosinophilia and 17% combined systemic and airway eosinophilia) and confirmed that patients with both systemic and airway eosinophilic inflammation had poorer asthma control compared with noneosinophilic asthma (mean¡SEM ACQ score 2.23¡1.40 versus 1.79¡1.12; mean difference 0.44, 95% CI 0.007–0.89 (p,0.05)) (fig 2). In the prospective cohort, patients exhibiting diffuse eosinophilic inflammation had a higher number of exacerbations in the year prior to the visit to the asthma clinic (mean¡SD 1.11¡1.65, n541) than noneosinophilic patients (mean¡SD 0.77¡2.55, n5111) (p,0.05). Interestingly, for the whole cohort, the exacerbation rate over the 12 months following the asthma clinic visit decreased compared with that occurring in the year before (mean 0.86¡2.02 (95% CI 0.61–1.12) versus mean 0.50¡1.18 (95% CI 0.35–0.65) after) (p50.015) (see the online supplementary material for all details on ACQ score and exacerbation rate in the prospective cohort). Moreover, in the year following the visit to the asthma clinic, the number of exacerbations was significantly higher in patients advised to take high-dose ICS (mean¡SD 1.06¡1.63, n593) than in those advised to take low (mean¡SD 0.17¡0.62, n558) or moderate (mean¡SD 0.15¡0.40, n555) doses of ICS or not to take ICS at all (0¡0, n531) (p,0.0001). TABLE 3 Retrospective cohort: demographic and treatment characteristics of asthmatics (n5508) according to blood and sputum eosinophil count Blood eosinophils ,400 cells per mm, sputum eosinophils ,3% Blood eosinophils ,400 cells per mm, sputum eosinophils o3% Blood eosinophils o400 cells per mm, sputum eosinophils ,3% Blood eosinophils o400 cells per mm, sputum eosinophils o3% Subjects 249 (49) 128 (25) 34 (7) 97 (19) Males/females n 78/171 54/74* 16/18 53/44*** Age years 52 (21–86) 53 (21–88) 51 (21–85) 51 (19–86) Age of onset ,12 years 22.6 27.6 26.5 23.3 12–40 years 34.5 36.2 32.3 45.6 o40 years 42.9 36.2 41.2 31.1 Height cm 166¡9 168¡9 169¡9 169¡9 Weight kg 73¡16 74¡15 76¡17 75¡17 BMI kg?m 26.3¡5 26.4¡5 26.3¡4.8 26.4¡5.3 Atopy yes/no (%) 126/123 (51) 82/46 (64)* 22/12 (65) 66/31 (68)** Current smokers 54 (22) 29 (23) 6 (18) 12 (12)* Bronchiectasis 19 13 17 26 Gastro-oesophageal reflux 77 81 86 77 Nasal polyposis 9 25*** 37*** 43*** Sinusitis 34 38 42 61*** Rhinitis 53 59 72 65 Exacerbations per patient per year 0.42¡0.9 0.93¡2.72* 0.59¡0.98 1.5¡2.5*** ICS Steroid naı̈ve 82 (33) 31 (24) 9 (26) 31 (32) Low dose 30 (12) 20 (16) 5 (15) 18 (19) Moderate 70 (28) 37 (29) 11 (32) 20 (21) High dose 67 (27) 40 (31)* 9 (26) 28 (29) Data are presented as n (%), median (range), % or mean¡ SD, unless otherwise stated. BMI: body mass index; ICS: inhaled corticosteroids. : comparator group; : n5174; : based on chest computed tomography (CT); : based on sinus CT and nasal endoscopy; : n5273; : during the year prior to the visit; : f500mg per day beclomethasone; : 500–1000mg per day beclomethasone; : .1000mg per day beclomethasone. *: p,0.05; **: p,0.01; ***: p,0.001. ASTHMA | F.N. SCHLEICH ET AL. DOI: 10.1183/09031936.00201813 5 When pooling both the retrospective and the prospective cohort (n5758), there was a weak but significant relationship between ACQ and sputum eosinophil count (r50.16, p,0.0001) but not between blood eosinophils and ACQ (r50.02, p50.57) (fig .4). Discussion The original finding of this study is that patients exhibiting both local and systemic eosinophilic inflammation had more severe asthma reflected by lower baseline lung function, higher bronchial responsiveness to methacholine, poorer asthma control and quality of life, and a greater number of TABLE 4 Retrospective cohort: functional characteristics, asthma control and quality of life of asthmatics (n5508) according to blood and sputum eosinophil count Blood eosinophils ,400 cells per mm, sputum eosinophils ,3% Blood eosinophils ,400 cells per mm, sputum eosinophils o3% Blood eosinophils o400 cells per mm, sputum eosinophils ,3% Blood eosinophils o400 cells per mm, sputum eosinophils o3% FEV1 % predicted 87¡19 83¡20* 84¡23 75¡19*** FEV1/FVC % 75¡10 72¡9* 77¡10 71¡10*** TLC % predicted 101¡16 101¡20 92¡21 103¡15 FRC % predicted 109¡29 108¡20 97¡30 101¡18 KCO % predicted 89¡19 92¡20 99¡14** 94¡26* PC20 mg?mL geometric mean (range) 3.99 (0.05–16) 2.32 (0.025–16)* 4.53 (0.05–16) 1.49 (0.05–16)** Reversibility % 8¡9 13¡14* 9¡12 17¡16*** ACQ score 1.88¡1.39 1.87¡1.19 1.98¡1.5 2.54¡1.45*** ,0.75 58 (23) 26 (20) 7 (21) 10 (10)** 0.75–1.5 45 (18) 30 (23) 10 (29) 15 (15) .1.5 146 (59) 72 (56) 17 (50) 72 (74)* AQLQ score 4.67¡1.36 4.84¡1.3 4.47¡1.26 4.3¡1.4* Data are presented as mean¡SD or n (%), unless otherwise stated. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; TLC: total lung capacity; FRC: functional residual capacity; KCO: transfer coefficient of the lung for carbon monoxide; PC20: provocative concentration of methacholine causing a 20% fall in FEV1; ACQ: Asthma Control Questionnaire; AQLQ: Asthma Quality of Life Questionnaire. : comparator group. *: p,0.05; **: p,0.01; ***: p,0.001. TABLE 5 Retrospective cohort: inflammatory characteristics of asthmatics (n5508) according to blood and sputum eosinophil count Blood eosinophils ,400 cells per mm, sputum eosinophils ,3% Blood eosinophils ,400 cells per mm, sputum eosinophils o3% Blood eosinophils o400 cells per mm, sputum eosinophils ,3% Blood eosinophils o400 cells per mm, sputum eosinophils o3% IgE kU?L 87 (1–7338) 211 (3–6785)*** 180 (13–2329)* 225 (1–17183)*** Blood eosinophils % 1.7 (0–5.4) 3.2 (0–7)*** 6 (0.3–15)*** 8 (0.4–30)*** Blood eosinophils per mm 140 (0–380) 250 (0–390)*** 490 (400–1220)*** 590 (400–3220)*** Blood neutrophils % 59 (27–82) 57 (34–91) 57 (41–76) 52 (32–67)*** Blood neutrophils per mm 4180 (76–11 080) 4370 (2290–15 410) 5040 (1760–10 010) 3965 (1820–8670) Sputum eosinophils % 0.3 (0–2.9) 9 (3–79)*** 0.6 (0–2.8) 26 (3.2–94)*** Sputum eosinophils per mm 2.7 (0–1020) 70 (6–5226)*** 4.8 (0–1796) 287 (5–33 375)*** Sputum neutrophils % 58 (0–100) 39 (0–90)*** 57 (0.2–99) 30 (0.2–91)*** Sputum neutrophils per mm 422 (0–73 440) 334 (1–9588) 560 (14–160 974) 259 (1–15 441) Fibrinogen g?L 3.2 (1.9–10) 3 (2–6) 3.3 (2.6–5) 3.4 (2.2–7) CRP mg?L 1.7 (0.2–10) 2 (0.2–14) 1.4 (0.5–4) 1.6 (0.2–13) FeNO ppb 17 (0–192) 37 (2–222)*** 32 (5–93)** 77 (11–247)*** Data are presented as median (range). CRP: C-reactive protein; FeNO: exhaled nitric oxide. : comparator group. *: p,0.05; **: p,0.01; ***: p,0.001. ASTHMA | F.N. SCHLEICH ET AL. DOI: 10.1183/09031936.00201813 6 exacerbations in the previous year. This suggests that the global magnitude of eosinophilic inflammation is a significant factor in disease severity. Another new finding of this study is that it provides figures on the proportion of asthmatics classified according to the site of eosinophilic inflammation. Overall, asthmatics without any sign of eosinophilic inflammation account for almost half of the patients while one-quarter to one-third had selective airway eosinophilia. Patients with systemic and airway eosinophilic inflammation represent one-fifth of the patients those with isolated systemic eosinophilic inflammation are rather rare. These proportions are found irrespective of asthma treatment received including high doses of inhaled corticoids. We believe our new classification based on eosinophilic inflammation is pertinent to the clinician and goes in line with the need to phenotype severe asthmatics as advocated by the recent ERS/ATS guidelines [32]. As mentioned, the link between eosinophils and asthma severity has been extensively debated. The first attempts to investigate this relationship were based on sampling BAL or biopsies during bronchoscopy. The invasive nature of the procedure has obviously limited the number of subjects studied, which may have led to contrasting results because of the interindividual patient variability. Being less invasive, the technique of induced sputum has considerably widened the series of patients investigated and has been key to the emergence of recognition of several inflammatory asthma phenotypes. Previous studies found higher levels B lo od o es in op hi l c ou nt p er m m 3 Male, atopic, high IgE levels, low FEV1 and FEV1/FVC, high BHR n=128 400 Sputum eosinophil count % High IgE levels n=34