Repeatability of cellular and soluble markers of inflammation in induced sputum from patients with asthma

Eosinophilic inflammation in stable chronic obstructive pulmonary disease. Relationship with neutrophils and airway function

The number and significance of airway eosinophils in stable COPD is controversial. Aims of this study were to evaluate airway inflammation in patients with stable COPD compared with other groups, and to examine the correlations between inflammatory markers and functional indices of airway obstruction. Cellular analysis and evaluation of eosinophil cationic protein (ECP) levels in induced sputum were made in 46 subjects (10 patients with clinically stable COPD, 15 patients with asthma, 11 asymptomatic smokers, and 10 healthy control subjects). As expected, eosinophils were significantly (p < 0.01) higher in patients with asthma (22.2%) than in other groups (COPD, 0.7%; smokers, 0.2%; control subjects, 0.2%), and neutrophils were significantly (p < 0.01) higher in patients with COPD (77.5%) than in the other groups (asthma, 26.7%; smokers, 33.1%; control subjects, 35.9%). However, eosinophils were also increased in patients with COPD, as compared with healthy controls (p < 0.05). Sputum ECP levels were significantly and similarly higher in both asthma and COPD groups than in the other two groups (p < 0.01). In patients with COPD and asymptomatic smokers, considered as a whole, good correlations were found between eosinophils and ECP, on the one hand, and between FEV(1) and the FEV(1)/FVC ratio, on the other. Our data suggest that eosinophils may be involved in the airway inflammation of COPD.

Lung function and sputum characteristics of patients with severe asthma during an induced exacerbation by double-blind steroid withdrawal

Some patients with severe asthma are difficult to control and suffer from frequent exacerbations, whereas others remain stable with anti-inflammatory therapy. To investigate mechanisms of exacerbations, we compared 13 patients 20 to 51 yr of age (11 female, two male) with difficult-to-control asthma (two or more exacerbations during the previous year) and 15 patients 20 to 47 yr of age (13 female, two male) with severe but stable asthma (no exacerbations) after matching for sex, age, atopy, lung function, airway responsiveness, and medication. Exacerbations were induced by double-blind, controlled tapering of inhaled corticosteroids (fluticasone propionate) at weekly intervals. FEV1, airway responsiveness for methacholine (PC20MCh) and hypertonic saline (HYP slope), eosinophils and soluble markers (ECP, albumin, IL-6, IL-8) in induced sputum were assessed at baseline and during exacerbation (peak flow < 60% of personal best), or after 5 wk if no exacerbation occurred. Steroid tapering caused a decrease (mean +/- SEM) in FEV1 (12.1 +/- 3.1% pred; p = 0.045), PC20MCh (2.1 +/- 0.4 doubling dose; p = 0.004) and HYP slope (1.7 +/- 0.3 doubling dose; p = 0.001), and an increase in sputum eosinophils (10 +/- 3%; p = 0.008) and soluble markers for the two groups combined, without significant differences between the groups. Patients with difficult-to-control asthma had more exacerbations than did the stable asthmatics during both steroid tapering (7 versus 2; p = 0.022) and corticosteroid treatment (6 versus 0; p = 0.003). Exacerbations during steroid treatment in the patients with difficult-to-control asthma were associated with a decrease in FEV1 and PC20MCh, but not in HYP slope or increase in sputum eosinophils. We conclude that tapering of inhaled corticosteroids induces a rapid, reversible flare-up of eosinophilic airway inflammation. Patients with difficult-to-control asthma may develop exacerbations despite treatment with inhaled corticosteroids, which appear to have an eosinophil-independent mechanism. This implies that assessment of the nature of exacerbations may contribute to improved treatment for these patients.

Sputum induction as a method of analyzing pulmonary cells: reproducibility and acceptability

Sputum induction has been proposed as a noninvasive method of sampling airway cells for assessing airway inflammation in asthma. Although useful in the research setting, the applicability of this technique to a respiratory clinic, where it might prove useful for clinical management of anti-inflammatory therapy, has not been assessed. We therefore studied the effect of sputum induction in terms of patient acceptability, effect upon airway caliber, and reproducibility of the total cell and differential cell count at 2 weeks in 20 asthmatic subjects first attending an asthma clinic. We compared such patients with normal controls. Thirty-seven subjects underwent sputum induction on two occasions (20 asthmatics and 17 normal subjects) separated by a 2-week interval, using a standardized protocol. Acceptability was assessed by questionnaire. Airway caliber was measured by serial spirometry, using albuterol premedication for asthmatic subjects. Sputum was induced by inhalation of 3.5% saline over 12 min. Total cell and differential counts on induced sputum were assessed and correlated with bronchial hyperresponsiveness, as well as reproducibility of the technique in the clinical setting. All subjects found the process acceptable, although mild side effects occurred in more than 90% of subjects. No differences in acceptability were found between asthmatic and normal subjects. Sputum induction was associated with a significant decrease in forced expiratory volume in 1 sec (FEV1) in normal subjects (from 4.1 +/- 0.17 to 4.02 +/- 0.19 L [p < 0.01] on visit 1 and on visit 2 from 4.01 +/- 0.15 to 3.90 +/- 0.16 L [p < 0.01]), but not in asthmatic subjects after albuterol premedication. Total pulmonary cell yield on the first and second sputum induction days was 1.97 +/- 0.06 x 10(6) cells/mL of sputum and 2.01 +/- 0.05 x 10(6) cells/mL of sputum, respectively, giving a reliability coefficient of 0.77. Less agreement was seen between individual cell differential counts within subjects, but most fell within the expected range on Bland-Altman plots. Sputum induction appears to be safe and acceptable in both normal and asthmatic subjects. A small decrease in FEV1 occurs in normal subjects, which is prevented by albuterol premedication in asthmatics. Reproducibility at 2 weeks yielded similar total numbers of pulmonary cells, but in a clinic population some variability was seen in the number of inflammatory cells, probably because of the small numbers of these cells. This technique may be less valuable in a clinical than a research setting.

Effect of inhaled steroids on airway hyperresponsiveness, sputum eosinophils, and exhaled nitric oxide levels in patients with asthma

BACKGROUND

Airway hyperresponsiveness, induced sputum eosinophils, and exhaled nitric oxide (NO) levels have all been proposed as non-invasive markers for monitoring airway inflammation in patients with asthma. The aim of this study was to compare the changes in each of these markers following treatment with inhaled glucocorticosteroids in a single study.

METHODS

In a randomised, double blind, placebo controlled, parallel study 25 patients with mild asthma (19-34 years, forced expiratory volume in one second (FEV1) >75% predicted, concentration of histamine provoking a fall in FEV1 of 20% or more (PC20) <4 mg/ml) inhaled fluticasone propionate (500 microg twice daily) for four weeks. PC20 to histamine, sputum eosinophil numbers, and exhaled NO levels were determined at weeks 0, 2, and 4, and two weeks after completing treatment. Sputum was induced by inhalation of hypertonic (4.5%) saline and eosinophil counts were expressed as percentage non-squamous cells. Exhaled NO levels (ppb) were measured by chemiluminescence.

RESULTS

In the steroid treated group there was a significant increase in PC20, decrease in sputum eosinophils, and decrease in exhaled NO levels compared with baseline at weeks 2 and 4 of treatment. Subsequently, each of these variables showed significant worsening during the two week washout period compared with week 4. These changes were significantly different from those in the placebo group, except for the changes in sputum eosinophils and exhaled NO levels during the washout period. There were no significant correlations between the changes in the three markers in either group at any time.

CONCLUSIONS

Treatment of asthmatic subjects with inhaled steroids for four weeks leads to improvements in airway hyperresponsiveness to histamine, eosinophil counts in induced sputum, and exhaled nitric oxide levels. The results suggest that these markers may provide different information when monitoring anti-inflammatory treatment in asthma.

Clinical control and histopathologic outcome of asthma when using airway hyperresponsiveness as an additional guide to long-term treatment. The AMPUL Study Group

According to international guidelines, the level and adjustment of antiinflammatory treatment for asthma are based solely on symptoms and lung function. We investigated whether a treatment strategy aimed at reducing airway hyperresponsiveness (AHR strategy) in addition to the recommendations in the existing guidelines (reference strategy) led to: (1) more effective control of asthma; and (2) greater improvement of chronic airways inflammation. To accomplish this, we conducted a randomized, prospective, parallel trial involving 75 adults with mild to moderate asthma who visited a clinic every 3 mo for 2 yr. At each visit, FEV1 and AHR to methacholine were assessed, and subjects kept diaries of symptoms, beta2-agonist use, and peak expiratory flow (PEF). Medication with corticosteroids (four levels) was adjusted according to a stepwise approach (reference strategy), to which four severity classes of AHR were added (AHR strategy). At entry and after 2 yr, bronchial biopsies were obtained by fiberoptic bronchoscopy. Patients treated according to the AHR strategy had a 1.8-fold lower rate of mild exacerbations than did patients in the reference strategy group (0. 23 and 0.43 exacerbation/yr/patient, respectively). FEV1 also improved to a significantly greater extent in the AHR strategy group (p </= 0.05). In bronchial biopsies this was accompanied by a greater reduction in thickness of the subepithelial reticular layer in the AHR strategy group than in the reference strategy group (mean difference [95% confidence interval (CI): 1.7 micrometers (0.2 to 3.1) micrometers]). The changes in AHR in both strategy groups were correlated with eosinophil counts in the biopsies (r = -0.48, p = 0.003). We conclude that reducing AHR in conjunction with optimizing symptoms and lung function leads to more effective control of asthma while alleviating chronic airways inflammation. This implies a role for the monitoring of AHR or other surrogate markers of inflammation in the long-term management of asthma.

Role of bronchoscopy in asthma research

Over the past 15 years, much has been learned about the presence of airway inflammation in asthma through the use of investigative bronchoscopy. It has become quite clear that inflammation is present even in mild asthma. In addition to the eosinophils, T-lymphocytes and a variety of cytokines have been identified to play a prominent role in asthmatic inflammation. The concept of delayed asthmatic response after allergen exposure and its relationship to cellular inflammation and airway hyper-reactivity has become more clearly established. Our understanding of asthmatic airway inflammation, however, is incomplete. As interesting as the database has been so far, investigative FB has not defined a unique profile for patients with asthma. Specifically, lavage or endobronchial biopsy has not identified parameters that help in the diagnosis, assessment of disease severity, prognosis, or likelihood to respond to specific therapies. Also, the exact relationship between parameters in lavage compared with mucosal biopsy and how these are related to airway hyper-reactivity and the clinical syndrome of asthma remains poorly understood. In this regard, it must be confessed that currently FB with lavage and biopsy in asthmatics needs to be considered as a research tool for specimen retrieval to help characterize and express inflammation. Although these techniques have contributed immensely to our understanding of asthma pathogenesis, presently these techniques do not have any practical role or clinical usefulness.

Between-observer repeatability of sputum differential cell counts. Influence of cell viability and squamous cell contamination

BACKGROUND

Induced sputum differential cell counts have been advocated as a method of noninvasively assessing airway inflammation in asthma and other airway diseases. Relatively little is known about the between-observer repeatability of sputum differential cell counts and the factors that influence it.

OBJECTIVE

To assess the between-observer variability of induced sputum cell counts.

METHODS

Sputum was induced and processed using standard techniques. Forty-two slides from 38 patients (31 with asthma, seven normal subjects) were randomly selected. Slides were classified as good (<20% squamous cells and >50% viability; n = 24); low viability (<50% viability; n = 10) and high squamous cell contamination (>20% squamous cells; n = 8). Two blinded observers counted between 200 and 400 nonsquamous cells and agreement was assessed by the intraclass correlation coefficient (ICC) and the standard deviation of between-observer differences (SD).

RESULTS

The overall ICC were 0.9, 0.89, 0.9 for eosinophils, neutrophils and macrophages and 0.29 and 0.69 for lymphocytes and epithelial cells. Repeatability was greater in slides classified as good compared with slides with low cell viability and particularly excess squamous cell contamination.

CONCLUSIONS

We have shown that the overall between-observer repeatability of the differential eosinophil, neutrophil and macrophage cell counts is good. Low cell viability and particularly excess squamous cell contamination reduce between-observer repeatability suggesting that techniques that ensure high cell viability and reduce squamous contamination would be an advantage.

Effect of differing doses of inhaled budesonide on markers of airway inflammation in patients with mild asthma

BACKGROUND

It is desirable to prescribe the minimal effective dose of inhaled steroids to control asthma. To ensure that inflammation is suppressed whilst using the lowest possible dose, a sensitive and specific method for assessing airway inflammation is needed.

METHODS

The usefulness of exhaled nitric oxide (NO), sputum eosinophils, and methacholine airway responsiveness (PC20) for monitoring airway inflammatory changes following four weeks of treatment with an inhaled corticosteroid (budesonide via Turbohaler) were compared. Mild stable steroid naive asthmatic subjects were randomised into two double blind, placebo controlled studies. The first was a parallel group study involving three groups receiving either 100 micrograms/day budesonide (n = 8), 400 micrograms/day budesonide (n = 7), or a matched placebo (n = 6). The second was a crossover study involving 10 subjects randomised to receive 1600 micrograms budesonide or placebo. The groups were matched with respect to age, PC20, baseline FEV1 (% predicted), exhaled NO, and sputum eosinophilia.

RESULTS

There were significant improvements in FEV1 following 400 micrograms and 1600 micrograms budesonide (11.3% and 6.5%, respectively, p < 0.05). This was accompanied by significant reductions in eosinophil numbers in induced sputum (0.7 and 0.9 fold, p < 0.05). However, levels of exhaled NO were reduced following each budesonide dose while PC20 was improved only with 1600 micrograms budesonide. These results suggest that exhaled NO and PC20 may not reflect the control of airway inflammation as accurately as the number of eosinophils in sputum. There were dose dependent changes in exhaled NO, sputum eosinophils, and PC20 to inhaled budesonide but a plateau response of exhaled NO was found at a dose of 400 micrograms daily.

CONCLUSION

Monitoring the number of eosinophils in induced sputum may be the most accurate guide to establish the minimum dose of inhaled steroids needed to control inflammation. This, however, requires further studies involving a larger number of patients.

Effect of methacholine challenge on cellular composition of sputum induction

BACKGROUND

Induced sputum and methacholine inhalation challenge are routinely used for the assessment of airway inflammation and airway hyperresponsiveness, respectively. This study investigates whether a methacholine challenge performed one hour before sputum induction alters the cellular and biochemical constituents of sputum.

METHODS

Sixteen stable asthmatic patients with lung function within the normal range underwent two sputum inductions within one week. One hour before one of the sputum inductions a methacholine challenge was performed.

RESULTS

There were no significant differences in total cell count, macrophages, neutrophils, eosinophils, lymphocytes, epithelial cells, ECP, and albumin between the two challenges. The repeatability of cell counts was good for all cells, ECP and albumin, but poor for total cells.

CONCLUSIONS

In patients with stable asthma a methacholine challenge carried out one hour before sputum induction does not significantly alter the cellular and biochemical constituents of sputum.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist, on allergen-induced airway responses and sputum cell counts in asthma

BACKGROUND

Cysteinyl leukotrienes are capable of inducing chemotaxis of eosinophils in vitro and within the airways of animals and humans in vivo.

OBJECTIVE

We hypothesized that montelukast (MK-0476), a potent cysLT1 receptor antagonist, would protect against allergen-induced early (EAR) and late (LAR) asthmatic responses by virtue of anti-inflammatory properties. Hence, we studied the effect of pretreatment with oral montelukast on allergen-induced airway responses. As an exploratory endpoint, changes in inflammatory cell differentials and eosinophil cationic protein (ECP) were evaluated in hypertonic saline-induced sputum.

METHODS

Twelve asthmatic men (20-34 years, FEV1 79-109% predicted, histamine PC20FEV1 <4 mg/mL) with dual responses to inhaled house dust mite extract participated in a two-period, double-blind, placebo-controlled, crossover study. Three oral doses of montelukast (10 mg) or matching placebo were administered 36 and 12 h before, and 12 h post-allergen. The airway response to allergen was measured by FEV1, and the EAR and LAR were expressed as the corresponding areas under the time-response curves (AUC0-3 h and AUC3-8h, respectively). During each study period, sputum was induced with 4.5% NaCl 24 h before and 24 h after a standardized allergen challenge. Processed whole sputum cytospins were stained with Giemsa, and cell counts expressed as percentage nonsquamous cells. ECP was measured by FEIA in sputum supernatants.

RESULTS

All subjects completed the study. The changes in baseline FEV1 were not significantly different between the two pretreatments (P = 0.183). Montelukast significantly inhibited the EAR and LAR, reducing the AUC0-3h by 75.4% (P<0.001) and the AUC3-8h by 56.9% (P = 0.003) as compared with placebo. Sputa of nine subjects could be included in the analysis (<80% squamous cells). Allergen challenge significantly increased sputum eosinophils after placebo (mean change +/- SD: 4.8 +/- 5.8%, P = 0.038), with a similar trend after montelukast (mean change +/- SD: 4.1 +/- 5.4%; P = 0.056). The allergen-induced changes in sputum eosinophils and ECP, however, were not significantly different between the two pretreatments (P = 0.652 and P = 0.506, respectively).

CONCLUSION

We conclude that oral montelukast protects against allergen-induced early and late airway responses in asthma. However, using the present dosing and sample size, this protection was not accompanied with changes in sputum eosinophil percentage or activity, which may require more prolonged pretreatment with cysLT1 receptor antagonists.

Inflammatory response after inhalation of bacterial endotoxin assessed by the induced sputum technique

BACKGROUND

Organic dusts may cause inflammation in the airways. This study was performed to assess the usefulness of the induced sputum technique for evaluating the presence of airways inflammation using inhaled endotoxin (lipopolysaccharide) as the inducer of inflammation.

METHODS

To characterise the inflammatory response after inhalation of endotoxin, 21 healthy subjects inhaled 40 micrograms lipopolysaccharide and were examined before and 24 hours after exposure. Examinations consisted of a questionnaire for symptoms, spirometric testing, blood sampling, and collection of induced sputum using hypertonic saline. Eleven of the subjects inhaled hypertonic saline without endotoxin exposure as controls. Cell counts, eosinophilic cationic protein (ECP), and myeloperoxidase (MPO) were determined in blood and sputum.

RESULTS

A significantly higher proportion of subjects reported respiratory and general symptoms after endotoxin inhalation. MPO and the number of neutrophils in the blood were higher and spirometric values were decreased after the lipopolysaccharide challenge. In the sputum MPO, ECP, and the numbers of neutrophils and lymphocytes were higher after the lipopolysaccharide challenge. No significant differences were found after the inhalation of hypertonic saline compared with before, except for a significantly lower number of lymphocytes in the sputum.

CONCLUSIONS

The results support previous studies that inhaled endotoxin causes an inflammation at the exposure site itself, as well as general effects. Sampling of sputum seems to be a useful tool for assessing the presence of airways inflammation, and the inhalation of hypertonic saline used to induce sputum did not significantly interfere with the results found after inhalation of lipopolysaccharide.

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.

Impaired perception of dyspnea in patients with severe asthma. Relation to sputum eosinophils

Poor dyspnea perception might be a risk factor for developing asthma exacerbations. We investigated whether severe asthmatics with recurrent exacerbations (brittle asthma) have different dyspnea perception and sputum cells compared with equally severe, but stable asthmatics, or patients with mild steroid-naive asthma. Fifteen brittle asthmatics (13 female, median age 28 yr [range, 20 to 47 yr]), 15 matched severe-stable asthmatics (14 female, median age 26 yr [range, 17 to 52 yr]), and 11 mild asthmatics (8 female, median age 25 yr [range, 19 to 43 yr]) underwent inhalation tests with methacholine (MCh), and hypertonic saline combined with sputum induction. Dyspnea was assessed by Borg and Visual Analogue Scale (VAS), plotted against the percent fall in FEV1, and expressed as the slope of the regression line (Slope-Borg and Slope-VAS). The brittle and stable asthmatics had poorer perception than patients with mild asthma (Slope-Borg [p = 0.036], Slope-VAS [p < 0.001] for MCh). In patients with brittle asthma the perception was less as compared with severe-stable asthma (Slope-Borg for MCh: p = 0.05). In the severe asthmatics there was an inverse correlation between sputum eosinophilia and Slope-Borg and Slope-VAS (R = -0.55, p = 0. 002 and R = -0.37, p = 0.049), whereas this correlation was a positive one in the mild asthmatics (R = 0.79, p = 0.012 and R = 0. 67, p = 0.05). In conclusion, patients with severe asthma, particularly those with recurrent exacerbations, have blunted perception of dyspnea, which is related to the degree of sputum eosinophilia. This suggests that increased sputum eosinophilia is an indicator of clinical instabililty, and that eosinophilic airways inflammation might affect dyspnea perception in severe asthma.

Peak flow variability and sputum eosinophilia in allergic rhinitis

BACKGROUND

Although some non-asthmatic subjects with allergic rhinitis exhibit airway hyperresponsiveness and increased diurnal peak expiratory flow (PEF) variation, little is known about the critical features that determine these physiologic alterations.

OBJECTIVE

In subjects with allergic rhinitis and methacholine hyperresponsiveness but no asthma symptoms, we examined whether there were features of asthmatic airway inflammation.

METHODS

Forty non-asthmatic adults (11 with allergic rhinitis and methacholine hyperresponsiveness, 20 with allergic rhinitis and normal methacholine responsiveness, and 9 healthy control subjects) were studied. Sputum was induced with inhaled hypertonic saline for 5-minute periods for up to 20 minutes. Plugs from the lower respiratory tract were selected for differential counting in cytocentrifuged preparations. For the next 14 days, subjects measured their PEF two times daily. Peak expiratory flow variation was expressed as amplitude % mean.

RESULTS

Peak expiratory flow variation was significantly higher in subjects with allergic rhinitis and methacholine hyperresponsiveness than in allergic rhinitis patients with normal methacholine responsiveness and healthy controls. Eosinophil counts in the induced sputum were significantly higher in the subjects with allergic rhinitis and methacholine hyperresponsiveness [median (interquartile range), 7.3 (9.0)%] compared with allergic rhinitis patients with normal methacholine responsiveness [2.5 (3.8)%, P = .03] and healthy controls [1.0 (1.0)%, P = .02].

CONCLUSION

We conclude that eosinophilic inflammation may be present in subjects with allergic rhinitis and airway hyperresponsiveness even when there are no symptoms of asthma. This could indicate that bronchial eosinophilia is insufficient to cause asthmatic symptoms.

CD11b and L-selectin expression on eosinophils and neutrophils in blood and induced sputum of patients with asthma compared with normal subjects

BACKGROUND

Patients with asthma show altered surface expression of the adhesion molecules CD11b and L-selectin on airway granulocytes compared with blood granulocytes.

OBJECTIVE

To investigate whether this modulation is related to disease activity or due to transendothelial migration, we compared the CD11b and L-selectin expression on blood and induced sputum eosinophils and neutrophils between patients with asthma and normal subjects.

METHODS

Eleven normal subjects (21-43 years), nine patients (21-34 years) with mild atopic asthma and 10 patients (20-47 years) with moderate to severe atopic asthma on regular treatment with inhaled steroids underwent sputum induction by inhalation of nebulized hypertonic saline (4.5%). CD11b and L-selectin expression on granulocytes from blood and DTT-homogenized sputum were analysed by flow cytometry. Eosinophils could be discriminated from neutrophils by using depolarized light scatter. Disease activity was assessed by baseline FEV1 and airway responsiveness to histamine (PC20).

RESULTS

Sputum eosinophils showed higher expression of CD11b (P<0.001) and lower expression of L-selectin (P<0.001) compared with peripheral blood eosinophils. CD11b and L-selectin expression on eosinophils from blood or sputum did not differ between the three groups. Similar results were obtained for neutrophils. The PC20 in the patients with moderate-to-severe asthma was related to CD11b expression on blood (R=-0.92, P=0.001) and sputum eosinophils (R=0.75, P=0.02).

CONCLUSIONS

Flow cytometry of induced sputum granulocytes from asthmatic as well as normal subjects is feasible. We conclude that the modulated expression of CD11b and L-selectin on airway granulocytes is not specific for asthmatic airway inflammation, but is probably the result of tissue migration per sé. This implies that CD11b and L-selectin expression on granulocytes in induced sputum cannot be used as marker of disease activity.

Changes in sputum composition during sputum induction in healthy and asthmatic subjects

BACKGROUND

Induced sputum is increasingly used to characterize the cellular and biochemical composition of the airways.

OBJECTIVE

We studied whether the composition of induced sputum is different between samples obtained sequentially during one sputum induction.

METHODS

Subjects with mild asthma (n=7) or healthy subjects (n=6) produced sputum during and after three consecutive 10 min periods of hypertonic saline inhalation. Samples were analysed separately for the three periods. To determine the reproducibility of the cellular composition, sputum induction was repeated on another two days.

RESULTS

The mean percentage of neutrophils decreased significantly (P<0.01) during sputum induction in asthmatic (36.9, 29.8, 16.3%) and healthy subjects (43.6, 17.2, 18.0%). Correspondingly, percentages of macrophages increased and percentages of eosinophils were 4.9, 3.5, and 3.7% in the asthmatic and 0.6, 0.7, and 0.5% in the healthy subjects, without significant change over the three periods; mean eosinophil numbers were significantly higher in the subjects with asthma (P< 0.05). Reproducibility of percentage cell counts did not markedly depend on sampling periods in terms of coefficients of variation. The concentration of eosinophil cationic protein decreased in both groups during sputum induction (P<0.01), geometric mean values being 579, 143, 57.4 microg L(-1) in the asthmatic and 130, 47.3, 28.4 microg L(-1) in the healthy subjects. Similar changes were seen for lactate dehydrogenase.

CONCLUSION

The separate analysis of induced sputum from three consecutive sampling periods of a single induction procedure demonstrated significant changes in their cellular and biochemical composition, both in healthy and mild asthmatic subjects.

Effect of repeated sputum induction on cell counts in normal volunteers

BACKGROUND

Sputum induction is becoming more commonly used to assess airway inflammation. Since it is a relatively non-invasive procedure it may be useful for repeated measurements over a short period of time.

METHODS

To assess the repeatability of the method over a 24 hour period, eight healthy, non-smoking, non-atopic subjects (four men) of mean age 30 years underwent sputum induction, repeated at eight hours and 24 hours. Sputum was induced by inhalation of 3.5% saline. Absolute and differential counts of inflammatory cells were performed on the whole sputum after dilution in Hank's balanced salt solution containing 1% dithiothreitol to solubilise the mucus content of the samples.

RESULTS

There was a significant rise in the percentage of neutrophils in the eight hour sample compared with the baseline (57%, range 25-94% at eight hours compared with 28%, range 19-60%: median difference 26%). The median baseline percentage of macrophages was 55% (range 26-69%) which fell to 38% (range 3-56%: median difference 22%) at eight hours and 19% (range 14-59%: median difference 25%) at 24 hours. There was no significant change in the differential counts of eosinophils, lymphocytes or columnar epithelial cells, nor in any of the absolute cell counts, at any time point.

CONCLUSIONS

Sputum induction may have limited utility in serial assessment of neutrophilic airway inflammation in normal subjects within a 24 hour period.

Comparison of two methods of processing induced sputum: selected versus entire sputum

Sputum analysis is increasingly used to assess airway inflammation in asthma. The analysis of sputum is currently performed with two techniques, i.e., analysis of selected sputum (plugs) and analysis of entire sputum. To investigate the diagnostic value of these two methods, we compared total and differential cell counts and supernatant eosinophil cationic protein (ECP) in selected and entire sputum collected on two occasions in a group of healthy and asthmatic subjects. We induced sputum with hypertonic saline in 18 asthmatics and in eight healthy subjects. On one occasion we analyzed selected sputum, and on another occasion we analyzed entire sputum. In each sample we measured total and differential cell counts and ECP concentration in supernatant. We found a higher percentage of eosinophils (15.3 versus 8.3%; p < 0.01), more viable nonsquamous cells (80.6 versus 71.8%; p < 0.01), and higher levels of ECP (548 versus 105 microg/L; p < 0.001) in selected sputum as compared with entire sputum, whereas the percentage of neutrophils was higher in the entire sputum (42.7 versus 33.3%; p < 0.05). The percentage of eosinophils and ECP concentration were significantly and similarly increased in both selected and entire sputum of asthmatic subjects, i.e., independent of the method of sputum analysis. In conclusion, the selected sputum method may indeed provide more viable cells, more eosinophils, and a higher concentration of ECP. However, both the selected sputum and the entire sputum method have the same diagnostic value in distinguishing asthmatics from healthy subjects.

Changes in sputum composition between two inductions performed on consecutive days

BACKGROUND

Sputnum induction is a non-invasive method for obtaining cellular and biochemical material from the airways and appears to be particularly suited for repeated testing. However, it has not been clarified whether repeated inductions lead to a change in sputum composition. The aim of this study was to compare induced sputum results between two inductions performed 24 hours apart.

METHODS

Ten subjects with mild asthma and 19 healthy subjects were included. Sputum was obtained during three consecutive 10 minute periods of hypertonic saline inhalation. Samples were analysed separately for the three inhalation periods. Corresponding pooled values were computed, taking into account total cell numbers of each inhalation period.

RESULTS

In the three consecutive inhalation periods mean (SE) percentages of neutrophils increased from 29.2 (4.2)%, 22.0 (4.6)% and 14.5 (2.9)% on day 1 to 43.1 (5.3)%, 34.8 (5.5)% and 25.7 (5.3)% on day 2 in healthy subjects and from 21.3 (4.3)%, 24.1 (5.9)% and 15.9 (3.7)% to 35.9 (6.9)%, 30.7 (7.1)% and 31.8 (6.5)% in asthmatic subjects. This parallel shift corresponded to a mean (95% CI) increase in the pooled percentages of neutrophils of 17.4 (11.6) to 23.3)% in healthy and 14.6 (1.2 to 28.0)% in asthmatic subjects. In contrast to neutrophils, the percentage of macrophages decreased from day 1 to day 2, while eosinophil and lymphocyte percentages did not change significantly.

CONCLUSION

These results suggest that the induction procedure itself causes a change in the composition of sputum detectable after 24 hours. This effect has to be taken into account when repeated sputum induction is performed.

Experimental rhinovirus 16 infection. Effects on cell differentials and soluble markers in sputum in asthmatic subjects

Asthma exacerbations are often associated with respiratory virus infections, particularly with rhinovirus. In the present study we investigated the effect of experimental rhinovirus 16 (RV16) infection on airway inflammation as assessed by analysis of hypertonic saline-induced sputum. Twenty-seven nonsmoking atopic, mildly asthmatic subjects participated in a placebo-controlled parallel study. RV16 (n = 19) or its diluent (n = 8) was nasally administered. Sputum inductions were performed at entry and on Days 2 and 9 after inoculation, and airway responsiveness to histamine (PC20) was measured on Days 4 and 11. Cell differentials and levels of albumin, eosinophil cationic protein (ECP), IL-8, and IL-6 were determined. The cellular origin of IL-8 was investigated by intracellular staining. RV infection was confirmed by culture and/or by antibody titer rise in each of the RV16-treated subjects. There were no significant changes in the sputum differentials of nonsquamous cells (MANOVA, p > or = 0.40). In the RV16 group, there was a significant increase in the levels of ECP, IL-8, and IL-6 at Day 2 after infection (p < 0.05), whereas the albumin levels did not change (p = 0.82). The levels of IL-8 and IL-6 remained elevated for as long as 9 d after infection (p < 0.05). The increase in the percentage of IL-8 positive cells at Day 2 after infection could be attributed to the increase in IL-8 positive neutrophils (p < 0.02). There was a significant decrease in PC20 at Day 4 (p = 0.02), which was no longer significant at Day 11 (p = 0.19). The decrease in PC20 correlated significantly with the increase in ECP in the first week (r = -0.60) and with the change in the percentage eosinophils in the second week after inoculation (r = -0.58). We conclude that experimental RV16 infection in atopic asthmatic subjects increases airway hyperresponsiveness in conjunction with augmented airway inflammation, as reflected by an increase in ECP, IL-8, and IL-6 in sputum. Our results suggest that the RV16-enhanced airway hyperresponsiveness is associated with eosinophilic inflammation.