Role of sputum differential cell count in detecting airway inflammation in patients with chronic bronchial asthma or COPD.

BACKGROUND: Sputum may provide an alternative source of bronchial cells to investigate characteristics of airway inflammation and its functional correlates in patients with asthma or chronic obstructive pulmonary disease (COPD). METHODS: Two groups of clinically stable patients were studied: a group of 43 patients with mild or moderate asthma and a group of 18 patients with COPD. Twenty normal subjects formed a control group. Sputum production was either spontaneous or induced with inhaled hypertonic saline for five minute periods for up to 20 minutes. The concentration of saline was increased at intervals of 10 minutes from 3% to 4%. Plugs from the lower respiratory tract were selected for differential counting in cytocentrifugation preparations. Bronchial provocation tests were performed by inhaling progressive concentrations of histamine from a DeVilbiss 646 nebuliser and the concentration of histamine which caused a 20% fall in the forced expiratory volume in one second (FEV1) was calculated (PC20FEV1). RESULTS: Neutrophils predominated in the sputum of subjects with COPD while eosinophils predominated in the sputum of those with chronic asthma. However, in 28% of asthmatic subjects an increased percentage of neutrophils was found. In asthmatic patients the differential count of eosinophils was inversely related to the FEV1, FEV1/VC, and bronchial hyperresponsiveness, and directly related to clinical scores. CONCLUSIONS: The cellular profile of sputum in normal subjects and in patients with asthma and COPD is different. The concentration of eosinophils in the sputum correlates with the severity of asthma.     

Comparison of spontaneous and induced sputum for investigation of airway inflammation in chronic obstructive pulmonary disease

BACKGROUND: Although sputum induction is used as a technique to investigate lower airway inflammation in asthmatic subjects, advantages over spontaneous sputum in patients with chronic obstructive pulmonary disease (COPD) have not been investigated. METHODS: Samples of spontaneous sputum and sputum induced with 3% hypertonic saline for 14 minutes were collected from 27 patients with chronic obstructive pulmonary disease (COPD) who usually produced spontaneous sputum. Spirometric indices and oxygen saturation (Sao2) were measured at seven minute intervals. The spontaneous, seven and 14 minute sputum samples were analysed for total and differential cell counts, cell viability, and interleukin 8 levels. RESULTS: Analysis of the sputum revealed that median cell viability was higher in the seven minute (62.8%; p = 0.004) and 14 minute (65%; p = 0.001) induced sputum samples than in spontaneous sputum (41.2%). There was no significant difference in total and differential cell counts or in interleukin 8 levels between spontaneous and induced sputum. During the sputum induction procedure the mean (SD) fall in forced expiratory volume in one second (FEV1) was 0.098 (0.111) 1 (p < 0.001) and in forced vital capacity (FVC) was 0.247 (0.233) 1 (p < 0.001). There was a small but significant fall in Sao2 during sputum induction (p = 0.03). CONCLUSIONS: Induced sputum contains a higher proportion of viable cells than spontaneous sputum. There are no significant differences between the sputum samples obtained at seven minutes and at 14 minutes of hypertonic saline nebulisation. Sputum induction is safe and well tolerated in patients with COPD.     

Evaluation of airway inflammation by quantitative Th1/Th2 cytokine mRNA measurement in sputum of asthma patients

BACKGROUND: Asthma is a chronic inflammatory disorder of the airways driven by T cell activation. Th2 cells and their cytokines are thought to play a role in the pathophysiology of allergic as well as non-allergic asthma. METHODS: Airway cells were obtained by sputum induction from 15 healthy and 39 asthmatic individuals and the airway T cell cytokine profiles (interleukin (IL)-4, IL-5, IL-13, IL-10 and interferon (IFN)-gamma) at the mRNA level were studied by real time RT-PCR. RESULTS: Asthma patients had increased expression of IL-5 (p = 0.001) and IL-13 (p = 0.03) mRNA in sputum compared with non-asthmatic controls. IL-4 mRNA and IFN-gamma mRNA were detectable in the sputum of 44% and 21% of patients, respectively, but not in controls. Sputum IL-10 mRNA levels did not differ significantly between patients and controls. Sputum mRNA expression levels of IL-4, IL-5, and IL-13 were significantly correlated with the percentage of eosinophils and were higher in subjects with allergic asthma than in those with non-allergic asthma (p = 0.03, p = 0.02 and p = 0.0002, respectively); they did not differ between mild asthmatic subjects and those with moderate to severe asthma. In contrast, IFN-gamma mRNA expression was higher in non-allergic than in allergic patients (p = 0.04) and higher in patients with moderate to severe asthma than in those with mild asthma (p<0.01). Sputum IL-5 mRNA levels (but not the other cytokine mRNA levels) were also correlated with exhaled nitric oxide (eNO) and with bronchial hyperreactivity expressed as the histamine concentration resulting in a 20% decrease in forced expiratory volume in 1 second. CONCLUSION: Real time RT-PCR analysis of mRNA in induced sputum confirms a predominance of Th2 cytokines in both allergic and non-allergic asthma. IL-5 levels reflect eosinophil infiltration as well as eNO levels and hyperreactivity, and levels of the Th1 cytokine IFN-gamma indicate asthma severity. The technique is a promising tool for use in further studies of asthma severity and disease activity.     

The airway microvasculature and exercise induced asthma.

It has been proposed that exercise induced asthma is a result of "rapid expansion of the blood volume of peribronchial plexi" (McFadden ER, Lancet 1990;335:880-3). This hypothesis proposes that the development of exercise induced asthma depends on the thermal gradient in the airways at the end of hyperpnoea. The events that result in exercise induced asthma are vasoconstriction and airway cooling followed by reactive hyperaemia. We agree that the airway microcirculation has the potential for contributing to the pathophysiology of exercise induced asthma. We do, however, question whether reactive hyperaemia, in response to airway cooling, is the mechanism whereby hyperpnoea provokes airways obstruction in asthmatic patients. Further, we question whether vasoconstriction accompanies dry air breathing and whether an abnormal temperature gradient and rapid rewarming of the airways are prerequisites for exercise induced asthma. From published experiments we conclude that dry air breathing is associated with vasodilation and increase in airway blood flow rather than vasoconstriction and a decrease in blood flow to the airways. We propose that the stimulus for the increase in airway blood flow is an increase in osmolarity of the airway submucosa. This osmotic change is caused by the movement of water to the airway lumen in response to evaporative water loss during hyperpnoea. The increase in airway blood flow may occur directly or indirectly by the osmotic release of mediators. Exercise induced asthma is most likely to be due to the contraction of bronchial smooth muscle caused by the same mediators. Whether it is enhanced or inhibited by alterations in airway blood flow is not yet established in man.     

Assessment of airway neutrophils by sputum colour: correlation with airways inflammation

BACKGROUND: Airway inflammation, with recruitment of neutrophils to the airway lumen, results in purulent secretions and a variety of potential adverse consequences for patients with chronic bronchitis and bronchiectasis. We hypothesised that gradations of sputum colour would correlate directly with the myeloperoxidase content of sputum and with various other indicators of the activity and consequences of bronchial diseases. METHODS: To test this hypothesis, we quantified sputum colour by reference to a sensitive nine point colour chart and correlated this assessment with indices of a number of inflammatory mediators in sputum. RESULTS: The results indicate that standardised visual measurements of sputum colour correlated strongly with myeloperoxidase, interleukin 8, leucocyte elastase (both activity and total quantity), sputum volume, protein leak, and secretory leucocyte proteinase inhibitor (p<0.001 for all). In addition, there was a strong direct correlation between leucocyte elastase and both myeloperoxidase (p<0.003) and sputum volume (p<0.001), but a strong negative correlation with secretory leucocyte proteinase inhibitor (p<0.001). CONCLUSIONS: These results indicate that sputum colour graded visually relates to the activity of the underlying markers of bronchial inflammation. The results of this simple visual analysis of sputum provides guidance concerning underlying inflammation and its damaging potential. It also provides a useful scientific tool for improving the monitoring of chronic airways diseases and response to treatment.     

Glutathione in induced sputum of healthy individuals and patients with asthma

BACKGROUND: Glutathione is central to the antioxidant defences of the lung. The aim of this study was to determine whether sputum induction can be used for the measurement of glutathione in the respiratory tract. METHODS: Saliva and induced sputum (3% NaCl, 20 minutes) samples were collected from 10 healthy individuals and 10 patients with stable asthma receiving treatment with inhaled corticosteroids. Samples were chilled on ice and dispersed by dilution with ice cold phosphate buffered saline and pipetting. Cell-free supernatants were obtained by centrifugation of samples and filtration of supernatants and analysed for total glutathione, glutathione disulfide, and albumin content. The cells were treated with dithiothreitol and cell numbers, cell viability, and differential cell patterns were determined. RESULTS: As judged by cell viability and percentage of non-squamous cells, adequate sputum samples were obtained from nine healthy and nine asthmatic subjects. The salivary total glutathione content was low (median concentration 1.2 microM (range 0.8-1.5) in healthy subjects and 0.9 microM (0.7-1. 2) in asthmatic subjects). The sputum total glutathione content of both healthy and asthmatic subjects was within the same range (3.9 (1.0-12.3) microM and 6.4 (1.3-19.2) microM, respectively; p=0.35). Surprisingly, and in marked contrast to results obtained with bronchoalveolar lavage, sputum levels of glutathione disulfide represented more than 50% of the total glutathione in both groups (50.9% (range 24.6-83.1) and 72.3% (range 36.5-97.4), respectively; p=0.2). CONCLUSIONS: The results of this study indicate that sputum induction can be used to measure the glutathione content of bronchial secretions. Sputum glutathione levels of stable asthmatic patients did not differ significantly from healthy controls.     

Exacerbations of asthma without sputum eosinophilia.

BACKGROUND--Sputum analysis provides a non-invasive method of examining the airway secretions of subjects with asthma in order to better understand the inflammatory process. Increased proportions of eosinophils are generally seen in the sputum of subjects with asthma, especially when there is an exacerbation. An unexpected observation in the sputum of subjects with mild exacerbations of asthma is reported. METHODS--Thirty four consecutive subjects with symptoms consistent with a mild exacerbation of asthma were recruited for a treatment study. Inclusion criteria required persistent symptoms of chest tightness, dyspnoea, or wheezing for two weeks (without spontaneous improvement or alteration in dose of inhaled corticosteroid) and a forced expiratory volume in one second (FEV1) that was reversible to more than 75% predicted or known best to ensure the exacerbation was mild. Sputum (spontaneous or induced with hypertonic saline) from all subjects was examined for differential cell counts. Eosinophilic sputum was defined as > or = 4% eosinophils on two occasions or > 10% eosinophils once. Clinical characteristics, sputum differential counts, and measurements of airways obstruction were compared between the subjects with and without sputum eosinophilia. RESULTS--Almost half of the subjects (16 of 34) considered to have mildly uncontrolled asthma had no sputum eosinophilia. In comparison with the subjects who had sputum eosinophilia the non-eosinophilic group had less airways obstruction (FEV1% predicted 88% v 70%) and less severe airways hyperresponsiveness (PC20 methacholine 0.45 mg/ml v 0.13 mg/ml). There was no difference between the groups in the type or prevalence of symptoms, history of recent infections, smoking, relevant allergen exposure, or use of inhaled corticosteroid. CONCLUSIONS--Symptoms of mildly uncontrolled asthma are not always associated with eosinophilic airways inflammation as measured by sputum analysis. The causes and treatment of the non-eosinophilic condition require further investigation.     

Ventilation heterogeneity is a major determinant of airway hyperresponsiveness in asthma, independent of airway inflammation

BACKGROUND: Airway hyperresponsiveness is the ability of airways to narrow excessively in response to inhaled stimuli and is a key feature of asthma. Airway inflammation and ventilation heterogeneity have been separately shown to be associated with airway hyperresponsiveness. A study was undertaken to establish whether ventilation heterogeneity is associated with airway hyperresponsiveness independently of airway inflammation in subjects with asthma and to determine the effect of inhaled corticosteroids on this relationship. METHODS: Airway inflammation was measured in 40 subjects with asthma by exhaled nitric oxide, ventilation heterogeneity by multiple breath nitrogen washout and airway hyperresponsiveness by methacholine challenge. In 18 of these subjects with uncontrolled symptoms, measurements were repeated after 3 months of treatment with inhaled beclomethasone dipropionate. RESULTS: At baseline, airway hyperresponsiveness was independently predicted by airway inflammation (partial r2 = 0.20, p<0.001) and ventilation heterogeneity (partial r2 = 0.39, p<0.001). Inhaled corticosteroid treatment decreased airway inflammation (p = 0.002), ventilation heterogeneity (p = 0.009) and airway hyperresponsiveness (p<0.001). After treatment, ventilation heterogeneity was the sole predictor of airway hyperresponsiveness (r2 = 0.64, p<0.001). CONCLUSIONS: Baseline ventilation heterogeneity is a strong predictor of airway hyperresponsiveness, independent of airway inflammation in subjects with asthma. Its persistent relationship with airway hyperresponsiveness following anti-inflammatory treatment suggests that it is an important independent determinant of airway hyperresponsiveness. Normalisation of ventilation heterogeneity is therefore a potential goal of treatment that may lead to improved long-term outcomes.     

Decreased peroxynitrite inhibitory activity in induced sputum in patients with bronchial asthma

BACKGROUND: The production of peroxynitrite, an extremely potent oxidant, is increased in inflammatory lung disease. It is therefore important to measure antioxidant activity against peroxynitrite in epithelial lining fluid to examine the physiological effects of peroxynitrite in the airways of patients with asthma. This study was designed to determine whether peroxynitrite inhibitory activity in induced sputum is correlated with clinical characteristics and airway inflammatory indices in asthmatic patients. METHODS: Inflammatory indices were measured in induced sputum from 25 patients with asthma and 12 normal control subjects. Peroxynitrite inhibitory activity was also measured by monitoring rhodamine formation in sputum samples. RESULTS: Peroxynitrite inhibitory activity in induced sputum was significantly lower in asthmatic patients (52.4 (24.5)%) than in normal control subjects (92.1 (3.9)%, p<0.0001). Its activity was significantly correlated with forced expiratory volume in 1 second (FEV(1)) % predicted (r=0.774, p<0.0001) and bronchial hyperreactivity to methacholine (r=0.464, p=0.023). There was a significant negative correlation between peroxynitrite inhibitory activity and the degree of eosinophilic airway inflammation (% eosinophils, r=-0.758, p<0.0001; eosinophil cationic protein, r=-0.780, p<0.0001). CONCLUSIONS: Decreased peroxynitrite inhibitory activity occurs in induced sputum of asthmatic patients. Since even in patients with stable asthma the airway lining fluid lacks peroxynitrite inhibitory activity, large amounts of peroxynitrite, which are further increased during an acute asthma attack, would not be completely inactivated and asthmatic airways might have markedly increased susceptibility to peroxynitrite induced airway injury.     

Markers of inflammation in induced sputum in acute bronchitis caused by Chlamydia pneumoniae

Little is known of the inflammatory characteristics of acute infections of the respiratory tract caused by virus and unusual bacteria such as Chlamydia pneumoniae. A case is reported in whom inflammatory indices in sputum were used to investigate, for the first time, the airway inflammation during an episode of acute bronchitis caused by C pneumoniae. The patient presented with a dry cough of five days duration. C pneumoniae was identified by polymerase chain reaction (PCR) in a nasopharyngeal swab collected on day 5. Virological studies were negative. Clinical and inflammatory indices in induced sputum were measured on days 6, 8, and 11. The cough cleared spontaneously by day 11. Forced expiratory volume in one second was normal throughout. Sputum findings identified intense airway inflammation characterised by increased total cell and lymphocyte counts followed by an increase in neutrophils and a decrease in the CD4/CD8 ratio, activation of CD8 lymphocytes, and exudation as indicated by an increase in fluid phase fibrinogen. These observations suggest that sputum might be useful to monitor an inflammatory/immune response of the airway in acute infections.


     

Analysis of induced sputum in adults with asthma: identification of subgroup with isolated sputum neutrophilia and poor response to inhaled corticosteroids

BACKGROUND: The debate as to whether asthma is a single or heterogeneous disease remains unresolved although pathological studies, mostly using fibreoptic bronchoscopy on small numbers of subjects, have emphasised the similarities between different clinical phenotypes. METHODS: Lower airway inflammation was assessed non-invasively using induced sputum in 34 normal controls and 259 adults with symptomatic asthma receiving treatment at steps 1-3 of the British Thoracic Society (BTS) guidelines. A subgroup of 49 patients treated with as required beta(2) agonists only who met BTS criteria for a step up in treatment were studied before and 2 months after treatment with inhaled budesonide 400 micro g twice daily. RESULTS: There was considerable heterogeneity in induced sputum cell counts, particularly in non-atopic patients. A subgroup of 60 patients had a distinctive sputum cell profile with a neutrophil count higher than our normal range (>65.3%) and a normal sputum eosinophil count (<1.9%). These patients were older, predominantly female, and were more likely to be non-atopic but otherwise had similar clinical and physiological features to the group as a whole. Among the 49 subjects studied before and after inhaled budesonide, 11 patients had an isolated sputum neutrophilia. Following treatment, these patients showed significantly less improvement in visual analogue symptom scores (-5.5 v -19.4 mm; mean difference 13.9; 95% CI 0.7 to 27.0), forced expiratory volume in 1 second (FEV(1)) (-0.08 v 0.13 l; mean difference 0.21; 95% CI 0.03 to 0.39), and concentration of methacholine provoking a fall in FEV(1) of 20% or more (PC(20)) (0.15 v 1.29 doubling doses; mean difference 1.11; 95% CI 0.13 to 2.15) than the remaining 38 patients. CONCLUSIONS: These results suggest the presence of a distinct subgroup of patients with mild to moderate asthma who have predominantly neutrophilic airway inflammation and who respond less well to treatment with inhaled corticosteroids.     

Non-invasive markers of airway inflammation as predictors of oral steroid responsiveness in asthma

BACKGROUND: Sputum eosinophil counts and exhaled nitric oxide (NO) levels are increased in asthma and both measurements fall in response to corticosteroids. METHODS: Exhaled NO levels and sputum eosinophil counts were assessed as non-invasive markers of the response to an oral steroid in 37 patients (19 women) with stable chronic asthma (mean (SD) age 48.6 (12.2) years, asthma duration 25. 9 (17.3) years, and baseline forced expiratory volume in one second (FEV(1)) 76.3 (21.9)% predicted). Spirometric tests, with reversibility to a beta agonist (2.5 mg nebulised salbutamol), and induced sputum (using nebulised 3% saline) were performed at recruitment and following treatment with 30 mg prednisolone/day for 14 days. RESULTS: Baseline NO levels correlated with the percentage improvement in FEV(1) from baseline to the post-steroid, post-bronchodilator value (r(s) = 0.47, p = 0.003), with an NO level of >10 ppb at baseline having a positive predictive value of 83% for an improvement in FEV(1) of > or =15% (sensitivity 59%, specificity 90%). Sputum eosinophilia (> or =4%) had a positive predictive value of 68% (sensitivity 54%, specificity 76%) for an increase in FEV(1) of > or =15%. A combination of sputum eosinophilia and increased NO levels resulted in a positive predictive value of 72% and a negative predictive value of 79% (sensitivity 76%, specificity 75%). CONCLUSION: Exhaled NO levels and sputum eosinophilia may be useful in predicting the response to a trial of oral steroid in asthma.     

Relationship between induced sputum eosinophils and the clinical pattern of childhood asthma

BACKGROUND: The relationship between the clinical pattern of asthma and airway inflammation in childhood asthma is poorly characterised, yet underpins the treatment recommendations in current asthma guidelines. A study was undertaken to examine the relationship between airway inflammation and clinical asthma in children. METHODS: Children with asthma (n=146) and healthy controls (C, n=37) were recruited from primary and specialist clinics. Sputum induction and hypertonic saline challenge were performed. RESULTS: As the frequency of asthma episodes in the past 12 months increased, there were significant increases in sputum eosinophils (median; infrequent episodic (IE) 1.5%, frequent episodic (FE) 2.3%, persistent (P) 3.8%, control (C) 1.0%; p=0.002), sputum eosinophil cationic protein (ECP) (IE 113 ng/ml, FE 220, P 375, C 139; p=0.003), and desquamated bronchial epithelial cells (IE 2.0%, FE 6.0%, P 5.0%, C 2.5%; p=0.04). Treatment intensity was also associated with increased sputum eosinophils (p=0.005). The relationships between other severity markers (current symptoms, lung function) were less strong. CONCLUSION: Children with more frequent episodes of clinical asthma exhibit increasing airway inflammation that is characterised by sputum eosinophilia and bronchial epithelial desquamation. The results support clinical assessment by frequency of wheezing episodes over the past 12 months when determining anti-inflammatory treatment requirements, and indicate that current symptoms are determined by mechanisms in addition to sputum eosinophilia.     

Role of inflammation in nocturnal asthma.

BACKGROUND--Nocturnal airway narrowing is a common problem for patients with asthma but the role of inflammation in its pathogenesis is unclear. Overnight changes in airway inflammatory cell populations were studied in patients with nocturnal asthma and in control normal subjects. METHODS--Bronchoscopies were performed at 0400 hours and 1600 hours in eight healthy subjects and in 10 patients with nocturnal asthma (> 15% overnight fall in peak flow plus at least one awakening/week with asthma). The two bronchoscopies were separated by at least five days, and both the order of bronchoscopies and site of bronchoalveolar lavage (middle lobe or lingula with contralateral lower lobe bronchial biopsy) were randomised. RESULTS--In the normal subjects there was no difference in cell numbers and differential cell counts in bronchoalveolar lavage fluid between 0400 and 1600 hours, but in the nocturnal asthmatic subjects both eosinophil counts (median 0.11 x 10(5) cells/ml at 0400 hours, 0.05 x 10(5) cells/ml at 1600 hours) and lymphocyte numbers (0.06 x 10(5) cells/ml at 0400 hours, 0.03 x 10(5) cells/ml at 1600 hours) increased at 0400 hours, along with an increase in eosinophil cationic protein levels in bronchoalveolar lavage fluid (3.0 micrograms/ml at 0400 hours, 2.0 micrograms/l at 1600 hours). There were no changes in cell populations in the bronchial biopsies or in alveolar macrophage production of hydrogen peroxide, GM-CSF, or TNF alpha in either normal or asthmatic subjects at 0400 and 1600 hours. There was no correlation between changes in overnight airway function and changes in cell populations in the bronchoalveolar lavage fluid. CONCLUSIONS--This study confirms that there are increases in inflammatory cell populations in the airway fluid at night in asthmatic but not in normal subjects. The results have also shown a nocturnal increase in eosinophil cationic protein levels in bronchoalveolar lavage fluid, but these findings do not prove that these inflammatory changes cause nocturnal airway narrowing.