Safety of inducing sputum in patients with asthma of varying severity

Thoracic Society of Australia and New Zealand position statement: The safe clinical use of sputum induction for bio-sampling of the lower airways in children and adults

Sputum induction is widely used in clinical settings for collection of biological samples from the lower airways. However, in recent years sputum induction has been associated with serious adverse events and even death. This position statement was commissioned by the Thoracic Society of Australia and New Zealand to address major adverse events of two deaths associated with sputum induction that have occurred in Australia in 2021, and outlines best practice for the safe use of sputum induction. The statement resulted from systematic literature searches by a multi-disciplinary group including respiratory physicians, nurses and physiotherapists (paediatric and adults focused). Consumers had input to an advanced draft of the position statement. The position statement covers indications for sputum induction, informed consent, scope of practice of personnel administering the procedure, infection control considerations, details about the sputum induction procedure, safety considerations and risk assessment in clinical settings.

Methodological Aspects of Induced Sputum

We aimed to conduct a state-of-the-art review of the current literature and offer further insights into the methodological aspects concerning induced sputum. The increasing popularity of sputum induction as a non-invasive and cost-effective method for obtaining lower airway secretions from patients who cannot produce sputum naturally has led to extensive research and applications in respiratory conditions like asthma and COPD. This technique allows for analysis of the cellular and biochemical components of the sputum to take place, providing insights into airway inflammation, immune cells, and help in predicting treatment response. Furthermore, induced sputum enables various analyses, including microRNA and gene expression studies and immunophenotyping. The procedure is generally safe and well tolerated, even in patients with airflow limitations; however, monitoring lung function is essential, especially in those with airway hyperresponsiveness. Optimal saline solution concentration and inhalation duration have been investigated, recommending a 15-20 min induction with hypertonic saline. Expectoration involves coughing at the end of each inhalation time. Careful handling during sputum processing is necessary for obtaining accurate results in cell cytology, immunocytochemistry, and in situ hybridization. Overall, induced sputum offers significant advantages as a preferred alternative for large-scale and repeated airway sampling, despite some technical demands and limitations.

Safety and tolerability of sputum induction in adolescents and adults with suspected pulmonary tuberculosis

Sputum induction by the inhalation of hypertonic saline may increase the yield of microbiological diagnosis of pulmonary tuberculosis (TB). This is particularly relevant in paucibacillary TB, such as in children or human immunodeficiency virus (HIV)-infected patients. Sputum induction must be shown to be safe and tolerable in community settings where invasive diagnostic methods are unavailable. The objective of this study was to describe the changes in physiological parameters and adverse events occurring during sputum induction in ambulatory adult and adolescent TB suspects recruited in community clinics. Sputum induction was performed in HIV-infected (n = 35) and HIV-uninfected (n = 67) TB suspects (n = 102). Oxygen saturation (%), blood pressure (mm Hg), heart rate (/minute), respiratory rate (/minute), and adverse events were monitored at baseline, continuously during the salbutamol pre-treatment and saline nebulization phases, and for 30 min afterwards. During nebulization, there was a statistically significant increase in oxygen saturation (1%, p < 0.0001), systolic BP (7 mm Hg, p < 0.0001), and diastolic BP (2 mm Hg, p = 0.008). Post-nebulization decrease in the systolic BP occurred (4 mm Hg, p = 0.016). These changes were not considered to be clinically significant. Eight minor, transitory, self-resolving adverse events occurred (labored breathing, n = 2; chest pain, n = 2; paroxysmal coughing, n = 1; elevated heart rate, n = 1; vomiting, n = 1; hypotension, n = 1), leading to procedure termination in four participants. No serious adverse events occurred. Induced sputum is safe, tolerable, and feasible in adult and adolescent TB suspects in a community healthcare setting.

The effect of Ginkgo Biloba extract on the expression of PKCalpha in the inflammatory cells and the level of IL-5 in induced sputum of asthmatic patients

To investigate the effect of the Ginkgo Biloba Extract (GBE) on the asthma and examine its possible mechanisms, 75 asthma patients were divided into 4 groups and the patients were respectively treated with fluticasone propionate for 2 weeks or 4 weeks, or treated with fluticasone propionate plus GBE for 2 weeks or 4 weeks. Fifteen healthy volunteers served as healthy controls. Sputum inhalation with inhaling hypertonic saline (4%-5%) was performed. Lung ventilatory function and forced expiratory volume in one second (FEV1) were measured. The numbers of different cells in induced sputum were calculated. The expression of PKCalpha in the cells was immunocytochemically detected and the percentages of positive cells in different cells were counted. Interleukin-5 (IL-5) in sputum supernatants was detected with enzyme-linked immunosorbent assay. The percentage of eosinophils, lymphocytes, PKCalpha positive inflammatory cells and the concentration of IL-5 in asthmatic patients were higher than those in the controls (P<0.05), and the eosinophils, lymphocytes, positive expression of PKCalpha and the level of IL-5 were significantly decreased in asthmatic patients after they were treated with fluticasone propionate or fluticasone propionate plus GBE. However, they were still significantly higher than those of the controls. Compared to the group treated with glucocorticosteroid for 2 weeks, no significant decrease was found in the percentage of eosinophils, lymphocytes, PKCalpha positive inflammatory cells and the IL-5 in the supernatant of induced sputum. Compared with the group treated with glucocorticosteroid for 2 or 4 weeks, significant decrease in the same parameters was observed in the group treated with fluticasone propionate and GBE for 4 weeks. The IL-5 level in the supernatant of induced sputum was positively correlated with the percentage of PKCalpha-positive inflammatory cells and the percentage of eosinophils in the induced sputum in asthma patient groups respectively (n=150, r= 0.83, P<0.01; n=150, r=0.76, P<0.01). The FEV1 was negatively correlated with the percentage of PKCalpha-positive inflammatory cells and the IL-5 levels in supernatant of induced sputum in asthma patients respectively (n=150, r=-0.77, P<0.01; n=150, r= -0.64, P<0.01). It is concluded that GBE could significantly decrease the infiltration of inflammatory cells such as eosinophils and lymphocytes in the asthmatic airway and relieve the airway inflammation. GBE may decrease the activation of the PKCalpha in the inflammatory cells and thereby decrease the IL-5 level in induced sputum. GBE may be used as a complement to the glucocorticosteroid therapy for asthma.

Noninvasive methods for assessment of airway inflammation in occupational settings

The present document is a consensus statement reached by a panel of experts on noninvasive methods for assessment of airway inflammation in the investigation of occupational respiratory diseases, such as occupational rhinitis, occupational asthma, and nonasthmatic eosinophilic bronchitis. Both the upper and the lower airway inflammation have been reviewed and appraised reinforcing the concept of 'united airway disease' in the occupational settings. The most widely used noninvasive methods to assess bronchial inflammation are covered: induced sputum, fractional exhaled nitric oxide (FeNO) concentration, and exhaled breath condensate. Nasal inflammation may be assessed by noninvasive approaches such as nasal cytology and nasal lavage, which provide information on different aspects of inflammatory processes (cellular vs mediators). Key messages and suggestions on the use of noninvasive methods for assessment of airway inflammation in the investigation and diagnosis of occupational airway diseases are issued.

[Analysis of induced sputum in refractory asthma]

Induction of sputum by inhalation of hypertonic or isotonic fluid makes possible the safe and noninvasive harvesting of airway cells from patients with asthma, regardless of disease severity. Analysis of sputum cells has helped to identify different phenotypes of refractory asthma and shown that such asthma can be eosinophilic, neutrophilic, or both. Elevated eosinophil levels in sputum indicate a risk of exacerbation if the corticosteroid dose is reduced in stabilized patients. Surveillance of eosinophilia levels as an indicator for corticosteroid adjustment in refractory asthma makes it possible to reduce the frequency of severe exacerbations.

Induced sputum as a tool for early detection of airway inflammation in connective diseases-related lung involvement

BACKGROUND

Induced sputum (IS) sampling is a safe and validated approach to study bronchial inflammation in chronic obstructive lung diseases. Although promising results have also been reported in various diffuse interstitial lung disorders, the potential use of IS in the assessment of connective tissue diseases (CTD)-related lung involvement has not yet been investigated.

AIM OF THE STUDY

To evaluate the clinical usefulness of IS in the early management of patients suffering from rheumatoid arthritis (RA) and systemic sclerosis (SSc) at the onset of respiratory symptoms.

PATIENTS AND METHODS

The study population included 19 patients (RA=12; SSc=7) and 14 age- and sex-matched healthy volunteers. Lung function testing, high resolution computed tomography (HRCT) of the thorax and IS collection were performed in all cases. Broncho-alveolar lavage (BAL) was obtained in selected patients.

RESULTS

IS samples from patients contained a significantly higher percentage of neutrophils and a lower percentage of macrophages compared to healthy subjects (p=0.002 and 0.001, respectively), while the total cell number showed no differences. In addition, sputa yielded both higher cell counts and higher neutrophils than BAL samples (p=0.02 in all instances). No correlations were found between IS findings and lung function parameters, HRCT and BAL findings.

CONCLUSIONS

This is the first study investigating the inflammatory cell pattern in IS from CTD patients with early clinical evidence of lung involvement. Future studies are needed to determine whether the assessment of airway inflammation adds significant information that may result in a relevant improvement of disease management.

Safety of sputum induction with hypertonic saline solution in exercise-induced bronchoconstriction

BACKGROUND

The safety of sputum induction (SI) is well described in stable asthma, but the safety of SI in exercise-induced bronchoconstriction (EIB) has not been established.

OBJECTIVES

Our goals were to examine the relationship between the severity of EIB and bronchoconstriction during SI, and to determine if SI conducted after exercise challenge increases the risk of excess bronchoconstriction during SI.

METHODS

SI was conducted in 32 patients with mild-to-moderate asthma (baseline FEV(1), 86 +/- 9% of predicted [mean +/- SD]) with EIB (15 to 63% reduction in FEV(1) following exercise challenge) following pretreatment with albuterol using 3% saline solution and repeated on a separate day 30-min after exercise challenge.

RESULTS

There was a reduction in peak expiratory flow rate (PEFR) during SI without exercise (mean maximum reduction vs baseline, 4.0% at 10 min; 95% confidence interval [CI], 1.0 to 7.1; p = 0.02) and during SI 30 min following exercise (mean maximum reduction vs baseline, 5.2% at 8 min; 95% CI, 1.0 to 7.5; p < or = 0.01); however, there was no difference between the PEFR reductions during SI without or following exercise challenge. The best predictor of reduction in PEFR during SI was the preprocedure FEV(1), while the severity of EIB was not associated with bronchoconstriction during SI.

CONCLUSIONS

We conclude that SI can be performed safely following exercise challenge in asthmatics with EIB, and that the severity of EIB prior to SI is not a major determinant of bronchoconstriction during SI.

Dyspnea assessment and adverse events during sputum induction in COPD

Background

The inhalation of normal or hypertonic saline during sputum induction (SI) may act as an indirect bronchoconstrictive stimulus leading to dyspnea and lung function deterioration. Our aim was to assess dyspnea and adverse events in COPD patients who undergo SI following a safety protocol.

Methods

Sputum was induced by normal and hypertonic (4.5%) saline solution in 65 patients with COPD of varying severity. In order to minimize saline-induced bronchoconstriction a protocol based on the European Respiratory Society sputum induction Task group report was followed. Dyspnea change was scored using the Borg scale and lung function was assessed by spirometry and oximetry.

Results

Borg score changes [median(IQR) 1.5(0–2)] were observed during SI in 40 subjects; 16 patients required temporary discontinuation of the procedure due to dyspnea-general discomfort and 2 did not complete the session due to dyspnea-wheezing. The change in Borg dyspnea score was significantly correlated with oxygen saturation and heart rate changes and with discontinuation of the procedure due to undesired symptoms. 19 subjects presented an hyperresponsive reaction (decline>20% from baseline FEV₁). No significant correlation between Borg changes and FEV₁decline was found. Patients with advanced COPD presented significantly greater Borg and oxygen saturation changes than patients with less severe disease (p = 0.02 and p = 0.001, respectively). Baseline FEV₁, oxygen saturation and 6MWT demonstrated significant diagnostic values in distinguishing subjects who develop an adverse physiologic reaction during the procedure.

Conclusion

COPD patients undergoing SI following a safety protocol do not experience major adverse events. Dyspnea and oxygen desaturation is more likely to occur in patients with disease in advanced stages, leading to short discontinuation or less frequently to termination of the procedure. Baseline FEV₁, oxygen saturation and 6MWT may have a prognostic value for the development of these adverse events and might be useful to be evaluated in advance.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Relationship between dendritic cells and activated eosinophils in induced sputum of asthmatics

It has been suggested that dendritic cells (DCs) are critical antigen presenting cells for eosinophilic airway inflammation in a mouse model of asthma, and cysteinyl leukotrienes may play a role in DC trafficking in asthmatics. We investigated whether the number of DCs is increased in the induced sputum of both atopic and nonatopic asthmatics and is related to activated eosinophil count in the sputum. Sputum was induced by inhalation of hypertonic saline in 9 atopic and 12 nonatopic asthmatics and 10 nonatopic normal controls, and differential cell counts were performed. DCs and activated eosinophils were identified by immunocytochemistry with monoclonal antibodies (anti-CD1a and EG2, respectively). There were significantly higher percentages of eosinophils, EG2+ cells, and CD1a+ DC in the sputum of atopic and nonatopic asthmatics compared with normal controls, respectively. In asthmatics, the percentage of CD1a+ DC was significantly correlated with that of EG2+ cells (Rs=0.62, p=0.004). We demonstrated that the increased number of DCs was evident in the induced sputum of both atopic and nonatopic asthmatics, and the DC number was related to the activated eosinophil count, which suggests that DCs may contribute to the ongoing eosinophilic inflammation in asthmatic airways, and vice versa.

Sputum induction as a research tool for the study of human respiratory mucus

The study objectives were to compare in vitro transportability and physical properties of respiratory mucus, obtained invasively by direct collection (DC) right after endotracheal intubation and non-invasively by sputum induction with 3% hypertonic saline solution inhalation (SI) 24 h before the anesthesia. Twenty-two patients with no pulmonary disease scheduled for elective abdominal surgical procedures were studied. The parameters analyzed and the main results are as follows. (1) Transportability by cilia (MCT), SI was higher than DC (0.94+/-0.25 and 0.62+/-0.25; P<0.001). There was a significant correlation between the two methods and DC could be estimated by: DC=0.21+(0.44 SI) (r=0.44; P<0.001). (2) Transportability by cough (CC), SI was higher than DC (68.23+/-32.1 and 33.58+/-19.04 mm; P=0.002). (3) Contact angle (CA), SI was lower than DC (10+/-3 degrees and 22+/-14 degrees ; P=0.025). (4) Rheological properties (no significant difference obtained between SI and DC). These results indicated that SI changes mucus physical properties and transportability in non-expectorators.

Comparison of three methods for differential cell count in induced sputum

BACKGROUND

Induced sputum (IS) using the cytospin technique has been extensively employed to characterize inflammatory airway diseases; however, procedures of cell enrichment based on cytospin increase the analytical costs and require slide processing within a short period of time after sampling.

STUDY OBJECTIVES

To compare three different techniques for cytologic analysis of IS, and to determine the time required by each method and the costs involved.

DESIGN

Cross-sectional study.

SETTING

Tertiary-care university hospital.

PATIENTS AND MEASUREMENTS

Eighty-nine patients with asthma and 11 subjects without asthma were submitted to increasing hypertonic saline solution concentrations of 2, 3, 4, and 5% for 7 min for sputum induction. Samples were smeared without treatment with 0.1% dithiothreitol (DTT) [technique A], after treatment with DTT (technique B), and after treatment with DTT and cytospin (technique C). All slides were air-dried and stained with Leishman stain. Two independent observers counted at least 200 inflammatory cells on each slide.

RESULTS

Eighty percent of the slides processed by techniques A and B and 65% of the slides processed by technique C represented sputum samples of acceptable quality. The eosinophil percentages in sputum obtained by techniques A and C were closely correlated, as also were those obtained by techniques B and C (r = 0.64 and r = 0.63, respectively; p < 0.01). There was a positive correlation for eosinophils when we compared techniques A and B (r = 0.57, p < 0.01). The neutrophil correlation was significant when the three techniques were compared (technique A vs technique B, r = 0.66; technique A vs technique C, r = 0.51; and technique B vs technique C, r = 0.57; p < 0.01). Bland-Altman analysis showed a good agreement for eosinophil and neutrophil counts when techniques A and B were compared to technique C.

CONCLUSIONS

The three techniques are good indicators of lung inflammation. Techniques A and B are less time consuming and are of lower cost.

Study of cytokine gene expression in small cell samples: use in induced sputum

Sputum examination is being increasingly used as a non-invasive method for the study of airway inflammation. However, the technical applications of sputum are still limited because of the small number of cells recovered. In attempt to extend applications of sputum examinations, we developed and standardised, the reverse transcriptase-polymerase chain reaction (RT-PCR), a sensitive and specific technique of detection of mRNA, in induced sputum samples. Total RNA were extracted from samples containing as few as 50 to 80,000 cells, using a phenol-chloroform extraction method. RT-PCR was successfully tested on beta-actin, interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and tumour necrosis factor-beta (TGF-beta) genes. This protocol provides a simple technique to extract total RNA from a few number of induced sputum cells. It permits the semi-quantitatively study of cytokine gene expression in airways with simple means.

Induced sputum in the investigation of airway inflammation of COPD

During the last decade, the method of sputum induction (SI) has offered the opportunity to study inflammation in patients with chronic obstructive pulmonary disease (COPD). This paper reviews methodological aspects of SI and summarizes its uses in the research of inflammation in COPD, including sputum cellularity and soluble markers. SI is a relatively safe, reliable, and reproducible technique, used to investigate different aspects of airway inflammation. Although various methods of induction and processing have been proved safe and highly reproducible, a generally accepted method is needed. Sputum analysis has given evidence for increased numbers of macrophages and neutrophils in COPD patients compared to normal subjects. In some studies, increased numbers of eosinophils have been also reported. Changes in various mediators have been found in sputum supernatant of COPD patients (IL-8, LTB-4 and TNF-a). The clinical usefulness of the method in the follow-up of the disease has not been explored extensively. A number of observations in patients with different clinical characteristics could be proven useful in identifying patterns of inflammation associated with different prognosis. Finally, SI could also guide treatment; such as, sputum eosinophilia in COPD could predict response to inhaled corticosteroids.

Sputum processing: a new method to improve cytospin quality

BACKGROUND

Sputum examination is being increasingly used as a non-invasive method for studying airway inflammation. However, the application of sputum still presents some methodological problems and the results of sputum analysis may be substantially flawed by salivary contamination, cell and mucus debris. In addition, much work is needed to deepen the possibility of extensive application of cell and molecular biology techniques to sputum analysis.

OBJECTIVE

In an attempt to improve the technique of sputum processing, we investigated the effect of: (i) 20 and 11 microm filtration in addition to 40 microm on salivary contamination; (ii) Percoll density gradient centrifugation on sputum slides quality; (iii) a culture medium (Minimum Essential Medium containing HEPES 22 mm, pH 7.4: MEM) as washing and suspension solution compared to PBS on cell viability.

METHODS

Induced sputum samples were obtained in 37 asthmatics. 21 samples were processed as selected sputum and 16 samples as entire expectorates. After dithiotreitol (DTT) homogenization, each specimen was aliquoted in two parts of equal volume. One portion was processed with the usual method, the other using a modified method: cell pellet was suspended in sterile MEM, filtered through 40, 20 and 11 microm net filters and separated from the residual debris by Percoll gradient centrifugation.

RESULTS

As compared to the current sputum processing this method resulted in: (i) no selective bronchial cellular loss; (ii) a significant decrease of salivary contamination, particularly in entire expectorates in which squamous cells were reduced from 47 (36) to 15.5% (20) as median values and interquartile range; (iii) a higher proportion of good quality cytospins; (iv) maintenance of cell viability over the time (88% vs. 81% in MEM and PBS, respectively) 1 h after sample collection.

CONCLUSION

In the present study we demonstrated that the proposed method is feasible and makes it possible to overcome most of the technical limits met with the commonly used method, pointing to a potential extension of induced sputum application for more sophisticated techniques.

Induced sputum: comparison between isotonic and hypertonic saline solution inhalation in patients with asthma

BACKGROUND

Sputum induction by hypertonic saline solution inhalation is widely used to study airways secretions in patients with asthma. However, hypertonic saline solution is a potent indirect bronchoconstrictor.

STUDY OBJECTIVES

We studied the validity of isotonic saline solution (0.9%) inhalation as a means to induce sputum by comparing it to hypertonic saline solution (4.5%) inhalation.

PATIENTS

Sixteen patients with moderate-to-severe asthma reporting a clinical history of mucus hypersecretion.

METHODS

Subjects underwent sputum induction twice at 1-week intervals. Saline solution (hypertonic or isotonic) was inhaled for three periods of 5 min. The parameters assessed in sputum samples were cell counts, sodium, eosinophil cationic protein (ECP), and albumin concentrations, osmolality, and pro-matrix metalloproteinase (MMP)-9 activity by zymography.

RESULTS

The maximal fall in peak expiratory flow during sputum induction was greater after inhalation of hypertonic saline solution than after inhalation of isotonic saline solution (p < 0.01). Each subject produced analyzable sputum on both visits. There were no statistically significant differences in total and differential sputum cell counts, and the reproducibility coefficients were high for eosinophils and neutrophils when comparing the two methods. Likewise, sputum levels of ECP and albumin as well as sputum pro-MMP-9 activity were not different between the two methods, and were highly reproducible as shown by high intraclass coefficients (Ri) of correlation (0.72, 0.74, and 0.77 for ECP, albumin, and pro-MMP-9, respectively). Sputum sodium concentrations and osmolality were higher after inhalation of hypertonic saline solution (p < 0.05).

CONCLUSION

In patients with moderate-to-severe asthma reporting a clinical history of mucus hypersecretion, inducing sputum by isotonic or hypertonic saline solution inhalation leads to comparable results in eosinophil and neutrophil cell counts and fluid phase mediators/proteins.

Safety of sputum induction with isotonic saline in adults with acute severe asthma

BACKGROUND

Sputum induction is a safe and effective technique to study airway inflammation in stable asthma. However, it has the potential to induce bronchospasm and the safety and efficacy of the technique in acute asthma has not been determined.

OBJECTIVE

The objective of this study was to evaluate the safety and efficacy of a protocol to induce sputum using isotonic saline in adults with acute exacerbations of asthma.

METHODS

Adults (n = 47) presenting to the emergency room with acute asthma and an FEV1 > 1.0 L underwent supervised sputum induction with 0.9% saline delivered by an ultrasonic nebuliser. Induction was ceased if there was a fall of 20% or greater from baseline FEV1.

RESULTS

Subjects had moderate to severe exacerbations of acute asthma. An adequate sputum sample was obtained in 87% of subjects. Four subjects ceased induction because of symptom distress. There was a fall > or = 20% in 28% of subjects. Bronchoconstriction was successfully reversed by salbutamol in all subjects. Predictors of significant bronchoconstriction were older age, use of ingested corticosteroids, and a requirement for high-dose nebulized salbutamol for the exacerbation. Maintenance long-acting beta2-agonist therapy protected against bronchoconstriction during sputum induction.

CONCLUSIONS

Sputum induction in acute asthma using isotonic saline is highly efficacious in obtaining an adequate sputum sample. There is the potential for significant bronchoconstriction to occur but this can be managed safely with minimal discomfort to subjects.

Increased detection of interleukin-5 in sputum by addition of protease inhibitors

The measurement of interleukin (IL)-5 in sputum is problematic, with interfering factors affecting immunoassay. The authors investigated whether sputum proteases could be acting as interfering factors by studying the effect of protease inhibitors (PI) on sputum IL-5 measurement. Induced sputa from 20 subjects with asthma were divided into aliquots, processed with and without protease inhibitors (in low and high concentrations) and the levels of IL-5 (spiked and endogenous) measured by enzyme immunoassay were compared. The concentration of sputum IL-5 was significantly increased by PI, with median (interquartile range) levels processed with no, low and high PI concentrations being 0 (0), 41.8 (75.6) and 66.1 (124.4) pg x mL(-1), respectively. There was also a significant increase in percentage recovery of spiked IL-5. Although high concentrations of PI reduced cell viability, there was no effect on total or differential cell counts and low concentrations of PI had no effect on cell counts or viability. Levels of endogenous interleukin-5 in sputum of asthmatic subjects can be significantly increased by the addition of protease inhibitors, and samples which would be regarded as negative for interleukin-5 without protease inhibitors may instead have considerable amounts of interleukin-5 detected.

Sputum induction in severe asthma by a standardized protocol: predictors of excessive bronchoconstriction

Sputum induction is a noninvasive method to evaluate airway inflammation. We investigated whether it can be safely and successfully performed in patients with severe, difficult-to-control asthma, and whether the patients at risk can be identified. Ninety-three severe asthmatics were included, all symptomatic despite inhaled corticosteroids (> or = 1,600 microg/d) and long-acting beta(2)-agonists > 1 yr. Patients with a postbronchodilator FEV(1) < 1 L and < 50% predicted were excluded from participation. Sputum induction was performed according to a strict protocol, using 0.9%, 3.0%, and 4.5% NaCl inhalation. In 74% (CI: 64 to 83%) of patients an adequate sputum sample could be obtained. Twenty-two percent (CI: 14 to 33%) developed excessive bronchoconstriction (decrease in FEV(1) > 15% from baseline) despite the continuing use of long-acting bronchodilators and pretreatment with 400 microg salbutamol. The decrease in FEV(1) was associated with increased use of rescue short-acting beta(2)-agonists in the previous 2 d (r(s) = 0.51, p = 0.002), lower postbronchodilator FEV(1) (r(s) = -0.31, p = 0.004), and lower provocative concentration of histamine causing a 20% reduction in FEV(1) (PC(20)) (r(s) = -0.52, p < 0.001). Recent use of short-acting beta(2)-agonist increased the risk for excessive bronchoconstriction 10.2-fold (CI: 1.2 to 109.8). In conclusion, sputum induction can be safely and successfully performed in patients with severe, difficult-to-control asthma if a standardized protocol is used. However, severe bronchoconstriction may occur despite regular use of long-acting beta(2)-agonist and pretreatment with salbutamol 400 microg. In particular, patients who have used additional short-acting beta(2)-agonists as rescue medication during the days preceding the induction, are at high risk.

Increased expression of the chemoattractant cytokines eotaxin, monocyte chemotactic protein-4, and interleukin-16 in induced sputum in asthmatic patients

BACKGROUND

Induced sputum from asthmatic patients has been recently used to assess inflammatory cells. We have previously reported an increased expression of Th-2-type cytokines in induced sputum of asthmatic patients. C-C chemokines, particularly eotaxin and monocyte chemotactic protein (MCP)-4, are associated with eosinophilic infiltration. Interleukin (IL)-16 is associated with chemotactic activity for CD4+ cells. Chemokine expression in BAL and bronchial biopsy specimens has been demonstrated in asthmatic airways, but not in induced sputum.

METHODS

We examined whether eotaxin, MCP-4, and IL-16 expression could be detected in induced sputum of asthmatic patients (n = 10), and whether the expression was increased compared to normal control subjects (n = 9). Eotaxin, MCP-4, and IL-16 immunoreactivity were determined by immunocytochemistry. In addition, inflammatory cells were investigated using markers for T cells (CD3), eosinophils (major basic protein [MBP]), macrophages (CD68), neutrophils (elastase), and epithelial cells (cytokeratin).

RESULTS

Our results showed that there was a significant difference in the percentages of MBP-positive and epithelial cells between asthmatic patients and normal control subjects (p < 0.05). However, there was no difference between these two groups in the percentage of CD3-, elastase-, and CD68-positive cells. Immunoreactivity for eotaxin, MCP-4, and IL-16 was expressed in the induced sputum of all asthmatic patients, and expression of these chemotactic cytokines was significantly greater than in control subjects (p < 0.001, p < 0.005, and p < 0.001, respectively).

CONCLUSIONS

This study showed that induced sputum could be used to detect chemokines in patients with bronchial asthma, and that the upregulation of chemotactic cytokines in the airways can be seen using noninvasive techniques.

Induced sputum: diagnostic value in interstitial lung disease

Induced sputum by inhalation of hypertonic saline solution is a noninvasive technique used to collect cellular and soluble material from lung airways. During the past decade, this method has been widely used to assess airway inflammation in asthma and chronic obstructive pulmonary disease, since it produces reliable results and compares favorably to other invasive techniques, such as biopsy and bronchoalveolar lavage (BAL). Induced sputum has been recently used to study interstitial lung disease (ILD), more specifically pneumoconiosis, sarcoidosis, and nongranulomatous ILD. Moreover, results from induced sputum supplied information comparable to BAL findings for occupational lung disease and were able to distinguish sarcoidosis patients from healthy subjects and from patients with nongranulomatous ILD. Although induced sputum had previously provided promising results in assessing patients with ILD, its diagnostic role has not yet been well defined. Further studies of the evaluation by induced sputum of grading of severity, follow-up of disease, and effects of treatment are needed. Additionally, to date no specific studies have been undertaken to evaluate the safety and functional effects of sputum induction on patients with ILD. In conclusion, we think that induced sputum can be used as a complementary tool to BAL both in research and in clinical monitoring of patients with ILD.

Noninvasive measurement of airway inflammation using exhaled nitric oxide and induced sputum. Current status and future use

The recent use of IS and the analysis of exhaled mediators such as NO are important steps forward in our ability to noninvasively assess airway inflammation without the need to resort to bronchoscopy. Exhaled NO and IS are complementary techniques that provide different information (Table 1). Induced sputum can provide knowledge regarding the cells and mediators participating in the inflammatory response, but is time consuming and expensive. Exhaled NO measurement is performed simply and quickly, and is a nonspecific marker of an inflammatory process. The initial capital costs of equipment for NO analysis are high, however. Once the problems of standardized collection and oropharyngeal contamination have been dealt with, BC may also prove to be an additional tool for the assessment of airway inflammation. It is likely that the next 10 years will see the establishment of these noninvasive tools for the clinical assessment of airway inflammation and oxidative stress, and change the entire way we manage asthma.

Eosinophil activation markers in induced sputum in asthmatics

OBJECTIVES

Eosinophils play an important role in asthmatic airway inflammation collaborately with other inflammatory cells. The present study was aimed to determine whether the eosinophil activation markers in induced sputum reflect the clinical status in asthmatics.

METHODS

The clinical severity and FEV1 were measured. Hypertonic saline induced sputum was obtained from 25 asthmatics and ten control subjects. We processed freshly expectorated sputum separated from saliva by treatment with an equal volume of dithiothreitol 0.1%, cytospins for cell count and special stain, and a collection of the supernatant for biochemical assay. We used a fluoroimmunoassay to detect eosinophil cationic protein (ECP), and a sandwich ELISA to detect interleukin (IL)-5.

RESULTS

Asthmatics, compared with control subjects, had a significantly higher proportion of eosinophils (25.6 +/- 4.6% vs 1.7 +/- 0.2%, p < 0.01) and higher levels of ECP (1117.8 +/- 213.9 micrograms/L vs 154.6 +/- 47.4 micrograms/L, p < 0.01) in their sputum. IL-5 was detected more frequently in asthmatics than in control subjects [11/25 (44%) vs 1/10 (10%), p < 0.05]. Moderate to severe asthmatics had a significantly higher proportion of eosinophils, higher levels of ECP and IL-5 compared to mild asthmatics. FEV1, FEV1/FVC were significantly correlated with the proportion of eosinophils and the levels of ECP and IL-5. Significant positive correlations were noted between the proportion of eosinophils and the level of ECP and IL-5. Sputum ECP level showed a significant positive correlation with IL-5 level.

CONCLUSION

These findings demonstrate that eosinophils and the eosinophil activation markers, such as ECP and IL-5 in induced sputum, are closely related to the clinical status in asthmatics. Induced sputum study may thus be useful in clinically measuring indices of airway inflammation in asthma.

Effect of sputum induction on spirometric measurements and arterial oxygen saturation in asthmatic patients, smokers, and healthy subjects

BACKGROUND

Sputum production induced by inhalation of hypertonic saline solution has been proposed as a technique to collect secretions and inflammatory cells from the airways of subjects with bronchial asthma or with a history of smoking. The aim of this study was to determine the effect of a sputum induction procedure on spirometric results and arterial oxygen saturation (SaO(2)) in asthmatic patients, smokers, and healthy subjects.

METHODS

We recruited 14 subjects suffering from asthma (11 men and 3 women; age range, 18 to 49 years), 14 subjects with a history of smoking (5 men and 9 women; age range, 23 to 64 years), and 9 healthy volunteers (7 men and 2 women; age range, 28 to 54 years). To obtain a sample of induced sputum, all subjects inhaled a mist of 3% hypertonic saline solution nebulized for 5 min and repeated the cycle no more than four times. Asthmatic patients were pretreated with 200 microg salbutamol (inhaled). During sputum induction, the transcutaneous SaO(2) was continuously measured and baseline, fall, and the differences between baseline and fall SaO(2) were recorded. Additionally, we measured the duration of mild desaturation (change in SaO(2), < 4%) and of marked desaturation (change in SaO(2), > 5%) in each subject. Finally, baseline FEV(1) and changes in FEV(1) as a percentage of baseline values were recorded in all subjects.

RESULTS

We found that baseline and fall SaO(2) values for the three groups were similar. However, in each group a significant mean change in SaO(2) was evident during sputum production (asthmatic patients, 6.0%; smokers, 5.3%; healthy subjects, 6.0%). Moreover, the mean durations of mild desaturation were 7 min, 21 s in asthma patients; 8 min, 24 s in smokers; and 7 min, 16 s in healthy subjects. Similarly, the durations of marked desaturation were 1 min, 25 s in asthmatic patients, 1 min, 19 s in smokers, and 1 min, 21 s in healthy subjects. The mean (+/- SD) fall in FEV(1) was not statistically different among the three groups (asthmatic patients, 1.36 +/- 5.6%; smokers, 7.58 +/- 11.76%; and healthy subjects, 0.05 +/- 9.6%). However, one smoker did experience excessive bronchoconstriction (fall in FEV(1), > 20%).

CONCLUSIONS

This study demonstrated a significant and comparable fall in SaO(2) during sputum induction by inhalation of hypertonic saline solution in asthmatic patients, smokers, and healthy subjects. The results suggest that subjects who are hypoxemic before sputum induction require SaO(2) monitoring during the procedure.

The safety and success rate of sputum induction using a low output ultrasonic nebuliser

Induced sputum differential cell counts have been advocated as a method of non-invasively assessing airway inflammation in asthma and other airway diseases. Since sputum induction usually involves delivering hypertonic saline via a high output ultrasonic nebulizer there have been concerns about its safety in asthma. There are relatively little data on the effects of sputum induction in large numbers of patients. We have examined the success rate and effect of sputum induction on forced expiratory volume in 1 sec (FEV1) in 100 inductions performed on 79 patients using a low output nebulizer. Thirty-seven patients had asthma, 29 had miscellaneous conditions (mainly chronic cough) and 13 were subjects without respiratory symptoms. Sputum was induced 10 min after 200 micrograms of inhaled salbutamol by sequential 5-min inhalations of 3, 4 and 5% saline delivered via a Fisoneb ultrasonic nebulizer and FEV1 was measured after each inhalation. Sputum induction resulted in a sample suitable for analysis in 92% of asthmatics, 90% of those with miscellaneous conditions and 100% of normal subjects. The mean (SEM) maximum per cent fall in FEV1 was 5.4% (0.1), 4.3%, (1.0) and 2.6% (1.1) in subjects with asthma, miscellaneous conditions and in asymptomatic subjects respectively. Only 13 inductions resulted in a > 10% fall in FEV1, and only three of these resulted in a > 20% fall. The maximum per cent fall in FEV1 did not correlate with baseline FEV1 % predicted (r = -0.17), the log sputum eosinophil count (r = -0.12), or the methacholine PC20 (r = -0.14). We conclude that sputum induction using a relatively low output ultrasonic nebulizer with premedication with salbutamol is successful and safe in the majority of patients with asthma and other airway conditions.

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.