Sputum eosinophils and exhaled nitric oxide during late asthmatic reaction in patients with western red cedar asthma

Comparison of high- and low-molecular-weight sensitizing agents causing occupational asthma: an evidence-based insight

INTRODUCTION

The many substances used at the workplace that can cause sensitizer-induced occupational asthma are conventionally categorized into high-molecular-weight (HMW) agents and low-molecular-weight (LMW) agents, implying implicitly that these two categories of agents are associated with distinct phenotypic profiles and pathophysiological mechanisms.

AREAS COVERED

The authors conducted an evidence-based review of available data in order to identify the similarities and differences between HMW and LMW sensitizing agents.

EXPERT OPINION

Compared with LMW agents, HMW agents are associated with a few distinct clinical features (i.e. concomitant work-related rhinitis, incidence of immediate asthmatic reactions and increase in fractional exhaled nitric oxide upon exposure) and risk factors (i.e. atopy and smoking). However, some LMW agents may exhibit 'HMW-like' phenotypic characteristics, indicating that LMW agents are a heterogeneous group of agents and that pooling them into a single group may be misleading. Regardless of the presence of detectable specific IgE antibodies, both HMW and LMW agents are associated with a mixed Th1/Th2 immune response and a predominantly eosinophilic pattern of airway inflammation. Large-scale multicenter studies are needed that use objective diagnostic criteria and assessment of airway inflammatory biomarkers to identify the pathobiological pathways involved in OA caused by the various non-protein agents.

Inhalation Challenge Tests in Occupational Asthma: Why Are Multiple Tests Needed?

Occupational and environmental lung diseases are on the rise because of the widespread use of various toxic agents in industry. Asthma etiopathogenesis is unclear because of exposure to high and low molecular agents in workplaces. Approximately 15-25% of asthma in adults is reported to be related to occupational exposure. The prevalence of occupational asthma (OA) is predicted to be high. The difficulties in diagnosing OA results in inadequate treatment, permanent airway damage, and medicolegal and social problems. As with other occupational diseases, it is necessary to demonstrate a direct causal relationship between the suspected agent and OA. Spirometry, peak expiratory flow rate, and/or non-specific bronchial hyperresponsiveness are frequently used to show airway hyperresponsiveness at the workplace and away from work. However, there are some controversies about the specificity and sensitivity of these test methods. Furthermore, these tests do not identify the exposure agent, which could be the causative agent. Specific inhalation challenge (SIC) tests that demonstrate the direct causal relationship are currently the gold standard. However, their positive and negative predictive values have not yet been established; therefore, many low molecular weight agents could cause late or atypical reactions. Therefore, a negative SIC test cannot exclude the disease. This review describes the procedures for the SIC test and discusses the importance of using the combined test methods with the SIC test.

Work-Related Asthma

OBJECTIVE

Summarize developed evidence-based diagnostic and treatment guidelines for work-related asthma (WRA).

METHODS

Comprehensive literature reviews conducted with article critiquing and grading. Guidelines developed by a multidisciplinary expert panel and peer-reviewed.

RESULTS

Evidence supports spirometric testing as an essential early test. Serial peak expiratory flow rates measurement is moderately recommended for employees diagnosed with asthma to establish work-relatedness. Bronchial provocation testing is moderately recommended. IgE and skin prick testing for specific high-molecular weight (HMW) antigens are highly recommended. IgG testing for HMW antigens, IgE testing for low-molecular weight antigens, and nitric oxide testing for diagnosis are not recommended. Removal from exposure is associated with the highest probability of improvement, but may not lead to complete recovery.

CONCLUSION

Quality evidence supports these clinical practice recommendations. The guidelines may be useful to providers who diagnose and/or treat WRA.

Environmental factors associated with baseline and serial changes in fractional exhaled nitric oxide (FeNO) in spice mill workers

BACKGROUND

This study evaluated the determinants of high fractional exhaled nitric oxide (FeNO; >50 ppb) and serial changes in FeNO over a 24-hour period in spice mill workers at risk of work-related allergic respiratory disease and asthma.

METHODS

A cross-sectional study of 150 workers used European Community Respiratory Health Survey (ECRHS) questionnaires, Phadiatop, serum-specific IgE (garlic, chilli pepper, wheat; Phadia, ImmunoCAP), spirometry and FeNO. A hand-held portable nitric oxide sampling device (NIOX MINO, Aerocrine AB) measured FeNO before and after the 8-hour shift and after 24 hours from baseline.

RESULTS

The mean age of workers was 33 years; 71% were male, 46% current smokers and 45% atopic. Among workers with garlic sensitisation, 13% were monosensitised and 6% were co-sensitised to chilli pepper. Baseline preshift FeNO geometric mean (GM=14.9 ppb) was similar to the mean change across shift (GM=15.4 ppb) and across the 24-hour period (GM=15.8 ppb). In multivariate linear models, smoking (β=-0.507) and atopy (β=0.433) were strongly associated with FeNO. High FeNO (>50 ppb) was significantly associated with asthma-like symptoms due to spice dust (OR=5.38, CI 1.01 to 28.95). Sensitisation to chilli pepper was more strongly correlated with FeNO (r=0.32) and FeNO>50 ppb (OR=17.04, p=0.005) than garlic. FeNO increase (>12%) across 24 hours demonstrated a strong association with elevated exposures to spice dust particulate (OR=3.77, CI 1.01 to 14.24).

CONCLUSIONS

This study suggests that chilli pepper sensitisation is associated with high FeNO (>50 ppb), more strongly compared with garlic, despite the low prevalence of sensitisation to chilli. Elevated inhalant spice dust particulate is associated with a delayed elevation of FeNO across the 24-hour period.

Clinical and inflammatory features of asthma with dissociation between fractional exhaled nitric oxide and eosinophils in induced sputum

BACKGROUND

Measurement of the fractional exhaled nitric oxide (FeNO) and eosinophils in induced sputum are noninvasive markers for assessing airway inflammation in asthma. The clinical usefulness of the correlation between raised FeNO and sputum eosinophilia is controversial. We aimed to examine dissociation between FeNO and sputum eosinophils in a clinical series of asthma patients and to determine whether dissociation between these noninvasive markers was associated with clinical and inflammatory differences in these patients.

METHODS AND FINDINGS

A total of 110 patients with asthma were included in a cross-sectional study. All of them were on maintenance treatment for asthma. All patients underwent the following on the same day: FeNO, induced sputum, spirometry, serum total IgE levels and skin prick test. The level of asthma control was determined by the Asthma control Test Questionnaire. In 46 (41.8%) patients, a discrepancy between FeNO and sputum eosinophil count was observed, of those, 34 (73.9%) had a FeNO <50 ppb and high eosinophil count, and were characterized by having a predominance of nonallergic asthma with bronchial eosinophilic inflammatory phenotype. Also, 12 (26.1%) patients had FeNO ≥50 ppb and sputum eosinophilia within the normal reference values, and were characterized by having a predominance of atopy with a paucigranulocytic inflammatory phenotype.

CONCLUSIONS

A high percentage of patients with dissociation between results of FeNO and sputum eosinophils was observed. These patients showed differential clinical and inflammatory features.

Advanced diagnostic studies: exhaled breath and sputum analyses

AIM

: The present paper aims to review the advantages and limitations of sputum cell counts and exhaled nitric oxide (FeNO) levels in the investigation of occupational asthma (OA).

METHODS

The American College of Chest physicians held a course on occupational and Environmental Lung Diseases in Toronto in 2013. A summary of the session on non-invasive measures of airway inflammation in OA is presented here.

RESULTS

Occupational asthma is associated with an increase in sputum eosinophil percentage during periods at work or after positive specific inhalation challenges. Changes in FeNO are less sensitive than sputum eosinophil counts for predicting OA.

CONCLUSIONS

In settings where this tool is available, sputum eosinophil counts may complement the current investigation of OA. The interpretation of FeNO remains sometimes difficult. The phenotypes of patients who may benefit from this measure needs to be better defined.

When to suspect occupational asthma

Occupational asthma (OA) is a difficult diagnosis to make. The present review describes the work environments in which workers are at risk for developing OA, the characteristics of the individuals in whom OA should be suspected and the investigation that can be performed to diagnose the condition. Accurately diagnosing OA is crucial because of the major social and economic consequences of this diagnosis on the patient.

Airway gas exchange and exhaled biomarkers

During inspiration and expiration, gases traverse the conducting airways as they are transported between the environment and the alveolar region of the lungs. The term "conducting" airways is used broadly as the airway tree is thought largely to provide a conduit for the respiratory gases, oxygen and carbon dioxide. However, despite a significantly smaller surface area, and thicker barrier separating the gas phase from the blood when compared to the alveolar region, the airway tree can participate in gas exchange under special conditions such as high water solubility, high chemical reactivity, or production of the gas within the airway wall tissue. While these conditions do not apply to the respiratory gases, other gases demonstrate substantial exchange of the airways and are of particular importance to the inflammatory response of the lungs, the medical-legal field, occupational health, metabolic disorders, or protection of the delicate alveolar membrane. Given the significant structural differences between the airways and the alveolar region, the physical determinants that control airway gas exchange are unique and require different models (both experimental and mathematical) to explore. Our improved physiological understanding of airway gas exchange combined with improved analytical methods to detect trace compounds in the exhaled breath provides future opportunities to develop new exhaled biomarkers that are characteristic of pulmonary and systemic conditions.

Diagnostic approach in cases with suspected work-related asthma

BACKGROUND

Work-related asthma (WRA) is a major cause of respiratory disease in modern societies. The diagnosis and consequently an opportunity for prevention are often missed in practice.

METHODS

Based on recent studies and systematic reviews of the literature methods for detection of WRA and identification of specific causes of allergic WRA are discussed.

RESULTS AND CONCLUSIONS

All workers should be asked whether symptoms improve on days away from work or on holidays. Positive answers should lead to further investigation. Spirometry and non-specific bronchial responsiveness should be measured, but carefully performed and validly analysed serial peak expiratory flow or forced expiratory volume in one second (FEV1) measurements are more specific and confirm occupational asthma in about 82% of those still exposed to the causative agent. Skin prick testing or specific immunoglobulin E assays are useful to document allergy to high molecular weight allergens. Specific inhalational challenge tests come closest to a gold standard test, but lack standardisation, availability and sensitivity. Supervised workplace challenges can be used when specific challenges are unavailable or the results non-diagnostic, but methodology lacks standardisation. Finally, if the diagnosis remains unclear a follow-up with serial measurements of FEV1 and non-specific bronchial hyperresponsiveness should detect those likely to develop permanent impairment from their occupational exposures.

Diagnosis of occupational asthma: an update

Work-related asthma (WRA) includes patients with sensitizer- and/or irritant-induced asthma in the workplace, as well as patients with preexisting asthma that is worsened by work factors. WRA is underdiagnosed; thus, the diagnosis is critical to prevent disease progression and its potential for morbidity and mortality. The interview is the first diagnostic tool to be used by physicians, and the question, "Does asthma improve away from work?" is of the highest sensitivity. However, history can show numerous false positives, and the relationships between asthma worsening and work should be confirmed by objective methods such as peak expiratory flow (PEF) at and away from work. PEF sensitivity and specificity can be enhanced in combination with nonspecific bronchial hyperresponsiveness to histamine/methacholine (NSBP) before and after 2 weeks at work and a similar period off work. Immunologic testing, especially skin prick test (SPT) or specific IgE, is useful for high molecular weight allergens and some low molecular weight agents. Other immunologic tests, as well as induced sputum, measurement of exhaled nitric oxide, exhaled breath condensate, and specific inhalation challenge (SIC) are methods that contribute to the diagnosis and are typically performed at specialized facilities. A diagnosis of occupational asthma (OA) should no longer be based on a compatible history only but should be confirmed by means of objective testing. SIC is the diagnostic gold standard. When SIC is not available, the combination of PEF measurement, NSBP test , a specific SPT, or specific IgE may be an appropriate alternative in diagnosing OA.

Changes in exhaled nitric oxide levels after bronchial allergen challenge

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is a marker of inflammation of the airways accompanying changes in the clinical condition of asthma. Allergen exposure has been associated with a delayed elevation of FeNO. The aim of this study was to assess airway inflammation with FeNO measurements during bronchial allergen challenge (BAC), and to determine the diagnostic performance of FeNO changes.

METHODS

Thirty-four patients with asthma and sensitization to inhalant allergens were studied. BAC with common or high-molecular-weight occupational aeroallergens was performed. FeNO was measured before and 24 h after BAC. Receiver operating characteristics curve was built to assess the sensitivity and specificity of increase in FeNO levels associated with BAC outcome.

RESULTS

In 21 patients (61.76%) a positive asthmatic reaction (responders) was observed. A significant increase in postchallenge FeNO was observed in this group of patients compared to the group of nonresponders. A median increase (FeNO postchallenge-FeNO prechallenge) of 14.0 ppb was observed in the group of responders, whereas a -1.0 ppb change was attained in the nonresponder group (P < 0.001). The cutoff point providing maximal sensitivity and specificity for %ΔFeNO after BAC was 12%. This change in FeNO levels has a sensitivity of 0.81 and a specificity of 0.92 for predicting a positive outcome in the BAC.

CONCLUSION

FeNO measurements can be used as a surrogate of airway inflammation accompanying the asthmatic reaction induced by BAC. FeNO measurements may be a useful and reliable tool in the monitoring and interpreting specific bronchial challenge test with allergens.

An official american thoracic society statement: work-exacerbated asthma

RATIONALE

Occupational exposures can contribute to the exacerbation as well as the onset of asthma. However, work-exacerbated asthma (WEA) has received less attention than occupational asthma (OA) that is caused by work.

OBJECTIVES

The purpose of this Statement is to summarize current knowledge about the descriptive epidemiology, clinical characteristics, and management and treatment of WEA; propose a case definition for WEA; and discuss needs for prevention and research.

METHODS

Information about WEA was identified primarily by systematic searches of the medical literature. Statements about prevention and research needs were reached by consensus.

MEASUREMENTS AND MAIN RESULTS

WEA is defined as the worsening of asthma due to conditions at work. WEA is common, with a median prevalence of 21.5% among adults with asthma. Different types of agents or conditions at work may exacerbate asthma. WEA cases with persistent work-related symptoms can have clinical characteristics (level of severity, medication needs) and adverse socioeconomic outcomes (unemployment, reduction in income) similar to those of OA cases. Compared with adults with asthma unrelated to work, WEA cases report more days with symptoms, seek more medical care, and have a lower quality of life. WEA should be considered in any patient with asthma that is getting worse or who has work-related symptoms. Management of WEA should focus on reducing work exposures and optimizing standard medical management, with a change in jobs only if these measures are not successful.

CONCLUSIONS

WEA is a common and underrecognized adverse outcome resulting from conditions at work. Additional research is needed to improve the understanding of the risk factors for, and mechanisms and outcomes of, WEA, and to inform and evaluate preventive interventions.

Occupational and work-exacerbated asthma: similarities and differences

Over the years, there have been tremendous efforts to improve the understanding of occupational asthma (OA), whereas work-exacerbated asthma (WEA) has been somewhat overlooked. The aim of this work is to review the literature, comparing the prevalence of OA and WEA, their clinical and inflammatory characteristics, as well as the work environment of those suffering from OA and WEA. We performed a PubMed search up to September 2006 using the keywords: work-related asthma, WEA, work-aggravated asthma and OA. Only studies in English were included for consideration. We found that OA and WEA are prevalent conditions. The characteristics of subjects with OA and WEA vary according to the type of studies undertaken to describe these conditions. Many sensitizing agents have been reported to cause OA, whereas exposures to irritant agents seem to be associated with the occurrence of WEA. The inflammatory profile may differ between these two conditions, but the data are too limited and sometimes too contradictory to allow a firm conclusion to be drawn. The socioeconomic outcome of these conditions seems similar. Therefore, further studies investigating the prevalence of WEA, as well as its clinical, functional and inflammatory characteristics, are needed to improve the management of the workers with WEA.

Occupational asthma: risk factors, diagnosis and preventive measures

In adulthood, new or recurrent asthma is caused by work in approximately 10% of cases. The term occupational asthma is reserved for those cases arising from respiratory hypersensitivity to a specific workplace agent; in others (work-exacerbated asthma) the mechanism is of nonspecific airway irritation on a background of bronchial hyper-reactivity. Some 300 workplace agents are capable of inducing asthma de novo; fortunately, most cases are attributed to a much smaller number to which exposure occurs in a few high-risk occupations. Exposure level is the most important remediable risk factor; the factors governing individual susceptibility are poorly understood. Diagnosis is generally straightforward. Management is rarely pharmacologic and often difficult since the diagnosis incurs important employment and other social consequences.

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.

Investigation of occupational asthma: sputum cell counts or exhaled nitric oxide?

BACKGROUND

The measure of sputum eosinophil counts is a useful tool in the investigation of occupational asthma (OA), but processing sputum is time consuming. Measuring the fractional concentration of exhaled nitric oxide (FENO) may be an alternative in clinical practice. The aim of this study was to assess the respective changes of sputum eosinophil counts and FENO following exposure to occupational agents in the routine practice of two tertiary centers in North America and Europe.

METHODS

Workers undergoing specific inhalation challenges (SICs) for possible OA in tertiary clinics in both Canada and Belgium were enrolled. Sputum cell counts and FENO were collected at the end of the control day and at 7 and 24 h after exposure to the offending agent.

RESULTS

Forty-one subjects had a negative SIC; 26 subjects had OA proven by a positive SIC. In subjects with positive SIC, there was a significant increase in sputum eosinophils at 7 h (9.0 [9.9]%) and 24 h (11.9 [14.9]%) after exposure compared with the baseline (2.8 [4.2]%), whereas there was a significant increase in FENO only 24 h after exposure (26.0 [30.5] ppb) compared with the baseline (16.6 [18.5] ppb). A 2.2% change in sputum eosinophil counts achieved a much higher sensitivity and positive predictive value than a 10-ppb change in FENO with similar specificity and negative predictive value for predicting a 20% decrease in FEV(1) during SICs.

CONCLUSIONS

Sputum eosinophil counts constitute a more reliable tool than FENO to discriminate positive and negative SICs.

Occupational and environmental lung disease: occupational asthma

Occupational exposures cause 10-15% of new-onset asthma in adults, and that represents a considerable health and economic burden. Exposure to many causative agents is now well controlled but workplace practices are constantly evolving and new hazards being introduced. Overall, there is no good evidence that the incidence of occupational asthma is decreasing. Evidence-based guidelines such as those published by the British Occupational Health research Foundation and Standards of Care documents should help raise awareness of the problem and improve management. Key targets include the control of occupational exposures, a high index of suspicion in any adult with new onset asthma, and early detailed investigation.

Changes in sputum eicosanoids and inflammatory markers after inhalation challenges with occupational agents

BACKGROUND

An increase in cysteinyl-leukotrienes (LTs) after specific inhalation challenge (SIC) with common allergens in patients with atopic asthma has been shown previously, but there are scarce data with occupational agents. We sought to determine whether there are differences in lower airway inflammatory markers and the production of cytokines and eicosanoids between patients with a positive or negative SIC response to occupational agents.

METHODS

Twenty-six patients with suspected occupational asthma and 13 healthy control subjects were studied. Spirometry, methacholine challenge, and sputum induction were performed at baseline and 24 h after SIC with occupational agents. Several cytokines and inflammatory mediators, including eicosanoids, were measured in sputum.

RESULTS

Twenty-six SICs were carried out with high-molecular-weight or low-molecular-weight agents, and the responses were positive in 18 patients. SIC elicited nine early asthmatic responses, two dual asthmatic responses, and seven isolated late asthmatic responses. Significant increments in sputum eosinophil counts were found only in patients with positive SIC responses compared with baseline values. Interleukin-10 levels were decreased in patients with positive and negative SIC responses compared to those in healthy control subjects. A significant increase (p < 0.05) in the LTC(4)/prostaglandin E(2) (PGE(2)) ratio was observed in patients after positive SIC responses compared to those with negative SIC responses.

CONCLUSIONS

Overexpression of LTC(4), relative underproduction of PGE(2), and greater airway eosinophilia were observed in patients with positive SIC responses.

Sputum eosinophilia: an early marker of bronchial response to occupational agents

BACKGROUND

False-negative responses to specific inhalation challenge (SIC) with occupational agents may occur. We explored whether assessing changes in sputum cell counts would help improve the identification of bronchial reactivity to occupational agents during SICs.

METHODS

The predictive value of the changes in sputum cell counts after a negative FEV(1) response to a first challenge exposure to an occupational agent was determined using the changes in airway calibre observed during repeated challenges as the 'gold standard'. The study included 68 subjects investigated for work-related asthma in a tertiary centre. After a control day, the subjects were challenged with the suspected occupational agent(s) for up to 2 h. All subjects who did not show an asthmatic reaction were re-challenged on the following day. Additional challenges were proposed to those who demonstrated a > or = 2% increase in sputum eosinophils or an increase in nonspecific bronchial hyperresponsiveness to histamine after the second challenge day.

RESULTS

Six of the 35 subjects without changes in FEV(1) on the first challenge developed an asthmatic reaction on subsequent challenges. ROC analysis revealed that a >3% increase in sputum eosinophils at the end of the first challenge day was the most accurate parameter for predicting the development of an asthmatic response on subsequent challenges with a sensitivity of 67% and a specificity of 97%.

CONCLUSIONS

An increase in sputum eosinophils is an early marker of specific bronchial reactivity to occupational agents, which may help to identify subjects who will develop an asthmatic reaction only after repeated exposure.

Exhaled nitric oxide and breath condensate ph in asthmatic reactions induced by isocyanates

BACKGROUND

We investigated the usefulness of measurements of fractional exhaled nitric oxide (FeNO) and pH of exhaled breath condensate (EBC) for monitoring airway response after specific inhalation challenges with isocyanates in sensitized subjects.

METHODS

Lung function (FEV(1)), FeNO, and pH in argon-deaerated EBC were measured before and at intervals up to 30 days after a specific inhalation challenge in 15 subjects with isocyanate asthma, in 24 not sensitized control subjects exposed to isocyanates, and in 3 nonasthmatic subjects with rhinitis induced by isocyanate. Induced sputum was collected before and 24 h after isocyanate exposure.

RESULTS

Isocyanate-induced asthmatic reactions were associated with a rise in sputum eosinophil levels at 24 h (p < 0.01), and an increase in FeNO at 24 h (p < 0.05) and 48 h (p < 0.005), whereas FeNO level did not vary with isocyanate exposure in subjects with rhinitis and in control subjects. FeNO changes at 24 h positively correlated with corresponding sputum eosinophil changes (rho = 0.66, p < 0.001). A rise in pH was observed in the afternoon samples of EBC, irrespective of the occurrence of isocyanate-induced asthmatic reactions.

CONCLUSIONS

We demonstrated that isocyanate-induced asthmatic reactions are associated with a consistent delayed increase in FeNO but not with the acidification of EBC.

[The diagnosis and management of occupational asthma]

INTRODUCTION

Occupational asthma (OA), with a latency period induced by multiple exposures, is characterized by immunological sensitization to the responsible agent, based on both an IgE mediated mechanisms and non specific bronchial hyper responsiveness.

DIAGNOSTIC METHODS

In the diagnosis of OA, the medical history is obviously the starting-point. Onset of respiratory symptoms at work and resolution on vacation are indications of the diagnosis. After analysis of several publications, this element appears to have the best level of proof (grade 2+) according to the criteria of evidence-based medicine. A visit of the workplace, with the cooperation of the industrial physician, is essential to characterize the nature of the exposure. Positive immunological tests (skin tests and/or specific IgE) associated with objective criteria of symptoms related to work (modification of PEFR, lung function and/or nonspecific bronchial hyper responsiveness) will confirm the aetiological diagnosis of OA. Specific bronchial provocation tests performed in the laboratory allow the identification of new agents involved in OA and are necessary when other investigations are discordant or unavailable. OA needs a stepwise approach including induced sputum eosinophilic counts and measurements of exhaled nitric oxide.

MANAGEMENT OF OA

OA requires removal from the workplace because persistence of exposure to respiratory sensitisers may lead to an increase and prolongation of asthma symptoms. However, removal from the workplace can have tremendous professional, financial and social consequences, and sometimes a compromise must be found with reduction of exposure by various methods combined with adequate treatment. The pharmacological treatment of patients with OA should be the same as for patients with non OA, the use of bronchodilators and corticoids depending on the severity of asthma. Concerning the medico-legal aspects, OA can be recognised as an occupational disease. In France OA is included in several tables of work-related diseases.

Diagnosis and management of work-related asthma: American College Of Chest Physicians Consensus Statement

BACKGROUND

A previous American College of Chest Physicians Consensus Statement on asthma in the workplace was published in 1995. The current Consensus Statement updates the previous one based on additional research that has been published since then, including findings relevant to preventive measures and work-exacerbated asthma (WEA).

METHODS

A panel of experts, including allergists, pulmonologists, and occupational medicine physicians, was convened to develop this Consensus Document on the diagnosis and management of work-related asthma (WRA), based in part on a systematic review, that was performed by the University of Alberta/Capital Health Evidence-Based Practice and was supplemented by additional published studies to 2007.

RESULTS

The Consensus Document defined WRA to include occupational asthma (ie, asthma induced by sensitizer or irritant work exposures) and WEA (ie, preexisting or concurrent asthma worsened by work factors). The Consensus Document focuses on the diagnosis and management of WRA (including diagnostic tests, and work and compensation issues), as well as preventive measures. WRA should be considered in all individuals with new-onset or worsening asthma, and a careful occupational history should be obtained. Diagnostic tests such as serial peak flow recordings, methacholine challenge tests, immunologic tests, and specific inhalation challenge tests (if available), can increase diagnostic certainty. Since the prognosis is better with early diagnosis and appropriate intervention, effective preventive measures for other workers with exposure should be addressed.

CONCLUSIONS

The substantial prevalence of WRA supports consideration of the diagnosis in all who present with new-onset or worsening asthma, followed by appropriate investigations and intervention including consideration of other exposed workers.

Fractional exhaled nitric oxide in infants during cow's milk food challenge

Cow's milk allergy (CMA) is the most common food allergy in early childhood. The golden standard for the diagnosis of CMA is a food challenge after a period of elimination. Increased levels of fractional exhaled nitric oxide (FE(NO)) have been shown after bronchial allergen provocation. We evaluated whether FE(NO) may also be a predictor of a positive reaction during cow's milk challenge in infants. Forty-four infants [mean age (range): 4.2 (3.7-4.6) months] suspected of CMA underwent an open food challenge with cow's milk formula administered in ascending quantities, starting with 2 ml and then 6, 20, 60 and 200 ml until a clinical reaction occurred. Off-line FE(NO) samples were obtained during tidal breathing by means of a facemask covering infants' nose and mouth. FE(NO) was measured twice before the challenge (baseline), immediately before each new dose of milk and after a positive reaction or after the last dose of milk. Eleven children showed immediate positive clinical responses to cow's milk, whereas 13 infants presented only a late-type reaction. FE(NO) values before or after a positive reaction (either immediate or late) were not different from FE(NO) values at baseline. Baseline FE(NO) in infants with a positive reaction did not differ from FE(NO) in infants without a reaction at any time point. We conclude that FE(NO) values are not predictive and not related to the occurrence of a positive reaction during a cow's milk challenge in infants, suggesting that a positive reaction may not result from eosinophilic activation.

Partitioned exhaled nitric oxide to non-invasively assess asthma

Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperresponsiveness. Chronic repetitive bouts of acute inflammation lead to airway wall remodeling and possibly the sequelae of fixed airflow obstruction. Nitric oxide (NO) is a reactive molecule synthesized by NO synthases (NOS). NOS are expressed by cells within the airway wall and functionally, two NOS isoforms exist: constitutive and inducible. In asthma, the inducible isoform is over expressed, leading to increased production of NO, which diffuses into the airway lumen, where it can be detected in the exhaled breath. The exhaled NO signal can be partitioned into airway and alveolar components by measuring exhaled NO at multiple flows and applying mathematical models of pulmonary NO dynamics. The airway NO flux and alveolar NO concentration can be elevated in adults and children with asthma and have been correlated with markers of airway inflammation and airflow obstruction in cross-sectional studies. Longitudinal studies which specifically address the clinical potential of partitioning exhaled NO for diagnosis, managing therapy, and predicting exacerbation are needed.

Induced sputum and exhaled nitric oxide as noninvasive markers of airway inflammation from work exposures

PURPOSE OF REVIEW

Noninvasive measures of airway inflammation are increasingly used in the investigation and management of asthma. Their role in the investigation of occupational lung diseases, however, is not as clearly established. The present article reviews the use of noninvasive methods - induced sputum and exhaled nitric oxide - in the assessment of airway inflammation during the investigation of occupational asthma and eosinophilic bronchitis, and reviews studies investigating the effect of exposure to various occupational agents on airway inflammation in healthy individuals.

RECENT FINDINGS

A number of studies have confirmed the association between exposure to occupational agents and the presence of eosinophilic airway inflammation after that exposure in individuals with occupational asthma. Individuals with positive specific inhalation challenges to occupational agents seem to show a greater increase in exhaled nitric oxide than those with negative specific inhalation challenges. Exposure to various agents associated with an increase in exhaled nitric oxide mainly induced a neutrophilic inflammation.

SUMMARY

Increasing evidence supports the use of induced sputum as an additional tool in the investigation of occupational asthma. The role of exhaled nitric oxide in the investigation of occupational asthma needs to be clarified due to conflicting evidence reported in the literature.

New insights into occupational asthma

PURPOSE OF REVIEW

To examine recent publications on the types of agents involved in occupational asthma, the mechanisms by which they induce asthma, and how best to evaluate and treat workers suspected of this respiratory condition.

RECENT FINDINGS

High rates of occupational asthma and inhalation accidents were found in workers in crafts and related occupations in the manufacturing industries, and in plant and machine operatives; cleaners and construction workers may also be at risk. Further data support a role for CD4 T cells in low-molecular-weight agent-induced asthma, such as with isocyanates, and neurogenic mechanisms may also be involved. The use of noninvasive measures of airway inflammation in the diagnosis and management of occupational asthma such as sputum eosinophils monitoring is promising, although this is less obvious for exhaled nitric oxide. Finally, the persistence of troublesome asthma even after withdrawal from relevant exposure has been re-emphasized and surveillance programs have been proposed.

SUMMARY

Further data have been gathered on the prevalence of occupational asthma in various working populations, its mechanisms of development, the contribution of noninvasive measures of airway inflammation in the diagnosis and management of this condition, and its management and prevention.

Occupational asthma after withdrawal from the occupational allergen exposure

Occupational asthma is characterised by airway inflammation, variable airflow limitation and airway hyperresponsiveness related causally to work. The aim of the study was to ascertain whether in patients with occupational asthma findings persist after withdrawal from occupational allergen exposure. A group of 37 patients with occupational asthma and a control group of 19 persons were examined. Results in asthmatics obtained during the first visit when occupational asthma was acknowledged, were compared with recent results about 6.5 yr on average after elimination of occupational allergen exposure. Recent findings in occupational asthma patients were compared with the control group. In patients with occupational asthma, no significant differences were found between results obtained at the first and recent visit. Symptoms of asthma persisted in as much as 86.5% of patients. During recent examination there were more positive results in asthmatic patients comparing with the control group in histamine challenge (61.3 vs. 5.3%, p<0.01), eosinophile cationic protein (41.7 vs. 5.3%, p<0.05), prick tests (45.9 vs. 10.5%, p<0.05). Positive results of the present histamine challenge test and elevated eosinophils in sputum were more frequent (p<0.05) in patients with occupational asthma due to high molecular weight allergens than to low molecular weight allergens.

[Use of induced sputum in the investigation of occupational asthma]

The diagnosis of occupational asthma relies mainly on the demonstration of changes in airway calibre and airway responsiveness after exposure to occupational agents in the laboratory or at the workplace. However, spirometry or peak expiratory flow measurements may be open to misinterpretation when they are not performed optimally. As in non-occupational asthma, airway inflammation is one of the main characteristics of occupational asthma. Induced sputum, a non invasive method to assess airway inflammation, has been successfully used in the management of asthma. This article reviews the studies that have investigated and characterized the changes in sputum cell counts occurring in subjects with occupational asthma after exposure to occupational agents in the laboratory or at the workplace in order to assess the place of induced sputum in the investigation of occupational asthma. It also reviews the use of induced sputum during the follow-up of workers with occupational asthma after removal from exposure. This article also describes a new condition identified thanks to the use of induced sputum : occupational eosinophilic bronchitis. In conclusion, induced sputum is a useful tool in the investigation of occupational asthma. Its use on a regular basis in the investigation of occupational asthma also allows for the possibility of diagnosis of overlooked conditions such as occupational eosinophilic bronchitis. Its role in the surveillance of workers at risk to develop occupational asthma remains to be determined.

Diagnosing occupational asthma: insight from induced sputum

The diagnosis of occupational asthma needs to be made objectively using as many criteria as possible. The latter include laboratory exposure tests with occupational agent(s), which are only available in specialized centers. Another approach is to monitor peak expiratory flow (PEF) and (or) methacholine airway responsiveness during periods at work and away from work. However, these measurements are open to misinterpretation when they are not optimally performed. Airway inflammation is one of the main characteristics of asthma. Induced sputum, a non-invasive method to assess airway inflammation, has been successfully used in the management of asthma. However, airway inflammation is seldom assessed during the investigation of occupational asthma. This article reviews the studies that have investigated and characterized the changes in sputum cell counts occurring in subjects with occupational asthma after exposure to occupational agents in the laboratory, or at the workplace to assess to place of induced sputum in the investigation of occupational asthma.

Increase in exhaled nitric oxide (eNO) after work-related isocyanate exposure

The objective of this study was to evaluate the role of eNO changes post inhalative isocyanate challenge tests (DeltaeNO) with regard to specific asthmatic reactions and unspecific bronchial hyperresponsiveness (BHR) to predict clinical and subclinical responses of isocyanate workers.

METHODS

55 workers with isocyanate-related respiratory complaints (29 with BHR and 25 without BHR) underwent occupational-type challenge tests. We determined eNO before, during and up to 22 h after diagnostic isocyanate challenge.

RESULTS

The 12 asthmatic responders (22%) in the isocyanate-challenge test showed the highest eNO changes 22 h after challenge as well as a significant association between these changes and BHR. There was a positive association between an eNO increase of > 50% and an asthmatic response when compared to nonresponders with an odds ratio of 6.1; 95% CI 1.4-26.3; P = 0.02. More than half of the employees with BHR (52%) but only 20% of those without BHR developed an eNO rise of > 50% after 22 h. Furthermore, a significant positive association was found between the combination of BHR plus eNO increase of 50% after 22 h and the maximum sRaw change (% of baseline value) during the period 0-22 h after isocyanate exposure. The combination of BHR and eNO increase of > 50% was also associated with clinical symptoms during specific challenge tests (cough, shortness of breath, and/or rhinitis).

DISCUSSION AND CONCLUSIONS

An eNO increase 22 h post isocyanate challenge occurred in two-thirds of responders and in approximately half of nonresponders with BHR but only rarely in those without BHR. The combination of BHR and eNO increase in nonresponders may offer a new diagnostic tool to register subjects with an increased risk of developing occupational asthma. However, a large study group to perform follow-up investigations into this topic would be helpful to emphasize the importance of this finding.

Occupational asthma

Substantial epidemiologic and clinical evidence indicates that agents inhaled at work can induce asthma. In industrialized countries, occupational factors have been implicated in 9 to 15% of all cases of adult asthma. Work-related asthma includes (1) immunologic occupational asthma (OA), characterized by a latency period before the onset of symptoms; (2) nonimmunologic OA, which occurs after single or multiple exposures to high concentrations of irritant materials; (3) work-aggravated asthma, which is preexisting or concurrent asthma exacerbated by workplace exposures; and (4) variant syndromes. Assessment of the work environment has improved, making it possible to measure concentrations of several high- and low-molecular-weight agents in the workplace. The identification of host factors, polymorphisms, and candidate genes associated with OA is in progress and may improve our understanding of mechanisms involved in OA. A reliable diagnosis of OA should be confirmed by objective testing early after its onset. Removal of the worker from exposure to the causal agent and treatment with inhaled glucocorticoids lead to a better outcome. Finally, strategies for preventing OA should be implemented and their cost-effectiveness examined.

Exhaled nitric oxide in asthmatic children and adolescents after nasal allergen challenge

Epidemiological data suggest a comorbidity link between nasal and bronchial allergic disease. Exhaled nitric oxide (FENO) is a sensitive marker of bronchial inflammation and increases after bronchial allergen provocation. We studied FENO in 19 children and adolescents with allergic asthma and 10 controls before and 2, 6 and 24 h after a single nasal allergen challenge. The correlation between FENO and other markers of allergic inflammation, such as eosinophils in blood and eosinophil cationic protein (ECP) in serum and nasal lavage was also assessed. FENO remained unchanged 24 h post-challenge in both steroid and steroid-naive patients. At 6 h post-challenge, FENO decreased in both asthmatics and controls. The asthmatic subjects showed a positive correlation between FENO and blood eosinophils before (r=0.71, p=0.001) and after the challenge, and between FENO and ECP in nasal lavage (r=0.62, p=0.02) 2 h after the challenge. Mean ECP in nasal lavage increased post-challenge but not significantly. We conclude that a single nasal allergen challenge does not augment bronchial inflammation although FENO, is related to blood eosinophil count and to the nasal inflammatory response. Our data do not support the theory of a direct transmission of the nasal inflammation to the lower airways.

The use of sputum eosinophils in the evaluation of occupational asthma

PURPOSE OF REVIEW

The diagnosis of occupational asthma needs to be made objectively using as many criteria as possible. These include laboratory exposure tests with occupational agent(s), which are only available in specialized centres. Another approach is to monitor peak expiratory flow or methacholine airway responsiveness during periods at work and away from work. However, these measurements are open to misinterpretation when they are not performed optimally. Airway inflammation is one of the main characteristics of occupational asthma, but is not often assessed during its investigation. The purpose of this work was to review recent studies that have investigated and characterized the changes in sputum cell counts occurring in patients with occupational asthma, in order to evaluate the role of the analysis of sputum cell counts.

RECENT FINDINGS

There is evidence that monitoring sputum eosinophils can help in the management of asthma. In the majority of cases of occupational asthma, the percentage of sputum eosinophils increases after exposure to occupational agents in the laboratory compared with baseline, but an increase in sputum neutrophils has also been observed. The changes in airway inflammation occurring at the workplace have been less investigated, but indicate that there are significant changes in airway inflammation and especially sputum eosinophils when workers are exposed to a sensitizer at their workplace compared with periods away from the workplace.

SUMMARY

Induced sputum has successfully been used to manage patients with mild to moderate asthma. Its use is promising in occupational asthma, and its role in the investigation of occupational asthma needs to be better defined.

Eosinophilic bronchitis in the workplace

PURPOSE OF REVIEW

The purpose of this review is to report that eosinophilic bronchitis without asthma may occur as an occupational airway disease. This condition is characterized by cough that is responsive to corticosteroids and eosinophilia detectable in the sputum, without variable airflow obstruction or airway hyperresponsiveness.

RECENT FINDINGS

Eosinophilic bronchitis can be regarded as an occupational respiratory disorder when it develops as a consequence of work exposures. Recently, exposure to certain occupational allergens or sensitizers, such as natural rubber latex, mushroom spores, acrylates and an epoxy resin hardener, have been reported to cause eosinophilic bronchitis without asthma. Several hypotheses have been put forward trying to explain why patients with eosinophilic bronchitis do not have airway hyperresponsiveness. It is unknown whether eosinophilic bronchitis may progress to typical occupational asthma, or if eosinophilic airway inflammation may persist when asthma symptoms and airway hyperresponsiveness have waned after the cessation of exposure to the occupational agent.

SUMMARY

Eosinophilic bronchitis, like asthma, may arise from occupational exposures. The examination of induced sputum should be added to the objective monitoring of lung function during periods at work and away from work, as well as before and after specific inhalation challenges with occupational agents.

[Occupational asthma]

BACKGROUND

Occupational asthma (OA) is a frequent work-related disease in industrialised countries. It often leads to severe social and medical consequences.

TWO TYPES OF OA

A distinction must be made between OA with a latency period, the origin of which is essentially allergic, and OA without a latency period or Reactive airways dysfunction syndrome (RADS), induced by acute inhalation of irritant substances.

PREVALENCE

This is currently estimated as one case of asthma of occupational origin in one adult out of ten. In many cases its diagnosis is missed because it is not systematically searched for.

REGARDING DIAGNOSIS

Diagnosis, initiated on the results of questioning, must be supported by immunological tests whenever possible and notably on functional respiratory explorations (longitudinal monitoring of peak flow or spirometry, repeated measurements of non-specific bronchial reactivity), which objectifies significant variations in the parameters measured and related to professional activity. Bronchial challenge tests specifically identify the causal agent, but such examinations are long, expensive, potentially dangerous and therefore cannot be used in routine.

MANAGEMENT OF OA

Both social and medical, the management is aimed at stopping the exposure to the risk whilst protecting the person's employment. The declaration of occupational diseases is one of the principle measures of the medico-social care.

An effective strategy for diagnosing occupational asthma: use of induced sputum

Monitoring airway inflammation by means of induced sputum cell counts seems to improve the management of asthma. We sought to assess whether such monitoring at the end of periods at and away from work combined with the monitoring of PEF could improve the diagnosis of occupational asthma. We enrolled subjects suspected of having occupational asthma. Serial monitoring of PEF was performed during 2 weeks at and away from work. At the end of each period, induced sputum was collected. Specific inhalation challenge was subsequently performed. PEF graphs were interpreted visually by five independent observers. Forty-nine subjects, including 23 with positive specific inhalation challenge, completed the study. The addition of sputum cell counts to the monitoring of PEF increased the specificity of this test, respectively, by 18 (range [r] 13.7-25.5) or 26.8% (r 24.8-30.4) depending if an increase of sputum eosinophils greater than 1 or 2% when at work was considered as significant. The sensitivity increased by 8.2% (r 4.1-13.4) or decreased by 12.3% (r 3.1-24.1) depending on the cutoff value in sputum eosinophils chosen (greater than 1 or 2%, respectively). The addition of sputum cell counts to PEF monitoring is useful to improve the diagnosis of occupational asthma.

Inhalation challenge with bovine dander allergens: who needs it?

STUDY OBJECTIVES

To identify which tests would be useful in selecting patients for a specific inhalation challenge with bovine dander allergens (bSIC).

DESIGN

A prospective study.

SETTING

A university hospital.

PATIENTS

Thirty-seven dairy farmers with a clinical suspicion of occupational asthma due to bovine allergens.

INTERVENTIONS

Each patient (n = 27) underwent histamine challenge, mannitol challenge, exhaled nitric oxide (NO) measurement, bovine-specific serum IgE measurement, and skin-prick test (SPT) with bovine allergens prior to undergoing a bSIC.

RESULTS

Eleven patients responded to the inhalation challenge with bovine allergens. The sensitivity and specificity of the tests, based on this response, were 82% and 65%, respectively, for the histamine challenge; 20% and 94%, respectively, for the mannitol challenge; 27% and 77%, respectively, for the NO measurement; 82% and 100%, respectively, for the bovine-specific serum IgE measurement; and 100% and 50%, respectively, for the SPT. Multiple regression analysis revealed that only IgE-mediated sensitivity to bovine allergens, but neither bronchial hyperreactivity nor exhaled NO concentration, contributed significantly to the response.

CONCLUSION

Only the SPT with bovine allergens and bovine-specific serum IgE measurements were useful in selecting patients for the bSIC. This challenge should not be performed in SPT-negative subjects. A diagnosis of occupational asthma due to bovine dander allergens could be made without an inhalation challenge test in asthmatic patients with high bovine-specific serum IgE levels. This practice would eliminate the need for the majority of bSICs.

Diisocyanate-induced asthma: diagnosis, prognosis, and effects of medical surveillance measures

Diisocyanates have been the most commonly identified cause for occupational asthma (OA) in industrialized areas. Asthma among diisocyanate workers may be true occupational asthma, caused by a high level of irritant exposure at work or by sensitization to diisocyanates. Alternatively, asthma may be coincidental to or may be aggravated by work exposures. A clear diagnosis usually requires a combination of investigations (serial peak expiratory flow recordings, methacholine challenges, and/or diisocyanate challenges), but it is important to provide the best management by identifying whether workplace changes are needed for the worker. Preventive measures to reduce the risk of occupational asthma from diisocyanates have not been prospectively evaluated. The introduction of a medical surveillance program (in Ontario, Canada) in 1983 was followed by retrospective assessments to determine benefits. Between 1980 and 1993, the proportion of all accepted compensation claims for OA that were attributed to diisocyanates, classified by year of symptom onset in the province with the program, rose to 64 percent by 1988, then fell significantly down to 29 percent in 1992 and 35 percent in 1993. Besides the medical surveillance program for diisocyanates, possible factors contributing to this reduction may include reduced diisocyanates exposures and better awareness of diisocyanate-induced asthma, both by workers and physicians. Compared with OA caused by other agents, those with OA due to diisocyanates had a significantly earlier onset of asthma after the start of the exposure (mean 5 yr vs. 7 yr), were younger and less likely to be atopic and to have smoked. The mean duration of asthma before the main medical assessment for compensation was significantly shorter among those with diisocyanate-induced asthma (mean 2 yr vs. 3 yr), and the severity was milder as assessed by medication use and pulmonary function. Those with diisocyanate-induced asthma were significantly less likely to be hospitalized for asthma. Among the subset whose outcome was determined at a mean of 2.1 years after the main medical assessment, the outcome severity was less for those with diisocyanate-induced OA. Among those with diisocyanate-induced OA, an earlier diagnosis and a trend to better outcome was found in workers from companies that were identified to be in compliance with surveillance measures.

New developments in work-related asthma

Although work-related asthma is the most commonly recognized occupational lung disease, the condition remains underrecognized and underreported. New-onset occupational asthma and work aggravated asthma can have deleterious medical and socioeconomic consequences for the individual. Although interpretation and comparison between studies are hampered by the use of variable definitions of WRA and criteria for the diagnosis, as many as 20% of cases of new or aggravated adult asthma has important work-related factors. Thus, all asthmatic patients should be asked about their work, if their respiratory symptoms are worse when they work, or if a new job/exposure preceded the onset of symptoms. A series of longitudinal inception and apprentice cohort studies were undertaken to address significant weakness in the previous medical literature. These studies are just beginning to produce results, and provide strong evidence for asthma caused by exposure to specific occupational environments. They have begun to produce new understanding of the risk factors for developing OA, the natural history of OA and immune sensitization, and the existence of the healthy worker effect. New, non-invasive measures of airway inflammation have been developed with the potential for broad applications in the field of WRA. Although the measurement of exhaled NO and induced sputum analysis are primarily used as research tools, their place in clinical practice is likely to become clearer. These methods also have the potential to elucidate the various pathophysiologic mechanisms involved in WRA and may broaden our concept of occupational exposures that can initiate the onset of asthma.

Airway inflammation and functional changes after exposure to different concentrations of isocyanates

BACKGROUND

Isocyanates are a common cause of occupational asthma (OA).

OBJECTIVES

We sought (1) to examine whether asthmatic reactions to isocyanates could be induced at concentrations as low as 1 ppb in subjects with OA caused by isocyanates previously diagnosed in our center and (2) to compare the inflammatory and functional changes after exposure to 1 and 15 ppb of isocyanates with similar total doses (concentration of isocyanates x duration of exposure).

METHODS

Specific inhalation challenges were performed in 12 asthmatic subjects with previously confirmed OA caused by isocyanates. Eight subjects were exposed to 1 ppb at 10% of the dose of isocyanates that induced an asthmatic reaction at the time of the diagnosis. Seven subjects were exposed to the same total dose of isocyanates by using concentrations of 1 and 15 ppb 1 month apart.

RESULTS

Exposure to 1 ppb at 10% of the dose that had induced functional changes at the time of diagnosis induced an asthmatic reaction in 3 of 8 subjects. There was a significant correlation between the percentage of maximum decrease in FEV(1) after exposure to 1 ppb and the increase in sputum neutrophils (rho = 0.8). By keeping the total dose (concentration of isocyanates x duration of exposure) of isocyanates similar, 4 of 7 subjects experienced an asthmatic reaction after exposure to 1 ppb, whereas only one subject experienced an 18.5% decrease in FEV(1) after exposure to 15 ppb.

CONCLUSION

Isocyanates can induce functional and inflammatory changes (mainly neutrophilic) at concentrations as low as 1 ppb. For the same total dose of exposure, low concentrations of isocyanates are as harmful as or even more harmful than higher concentrations for subjects with OA to isocyanates.

Non-invasive assessment of airway inflammation in occupational lung diseases

The clinical investigation of occupational asthma is currently based on the demonstration of functional changes after exposure to occupational agents, but it does not yet include any monitoring of airway inflammation, one of the hallmarks of this disease. Methods permitting a non-invasive assessment of airway inflammation, such as induced sputum and exhaled nitric oxide, are currently under investigation for research purposes in occupational asthma. Their role in clinical practice has not yet been established. The advantages and limitations of these methods for occupational airway diseases, and more particularly occupational asthma, are discussed in this review.