Guidelines for bronchoprovocation on the investigation of occupational asthma. Report of the Subcommittee on Bronchoprovocation for Occupational Asthma

Prick testing with chemicals in the diagnosis of occupational contact urticaria and respiratory diseases

BACKGROUND

Little is known about the use of prick tests with chemicals in diagnosing occupational diseases.

OBJECTIVE

To evaluate the use of prick tests in the diagnosis of occupational contact urticaria, asthma and rhinitis caused by chemicals (undertaken at the Finnish Institute of Occupational Health).

MATERIAL AND METHODS

We retrospectively reviewed the patient and test files for the period 1 January 1991 to 31 May 2011. Prick tests were performed with chemical solutions and human serum albumin (HSA)-chemical conjugates.

RESULTS

Positive prick test reactions to isocyanate-HSA conjugates were associated with isocyanate-specific IgE in all 20 patients, and 17 patients had a relevant occupational disease. Positive reactions to chloramine-T-HSA conjugates in 10 patients also indicated the presence of specific IgE, although occupational diseases were not always diagnosed. Eleven of 17 patients with positive reactions to persulfate solutions were diagnosed with an occupational disease. Methacrylates, colophonium-related substances, amine hardeners, ethanolamines, glutaraldehyde, glyoxal, pyrocatechol and ammonium thioglycolate did not elicit any relevant prick test reactions. No generalized reactions were detected.

CONCLUSION

Prick tests can be safely used for diagnosing contact urticaria, asthma and rhinitis caused by isocyanates, chloramine-T, persulfates, and chlorhexidine, but the results should be carefully interpreted and related to clinical symptoms and other diagnostic tests.

Fractional exhaled nitric oxide in the interpretation of specific inhalational challenge tests for occupational asthma

PURPOSE

Fractional exhaled nitric oxide (FENO) measurements are recommended for the assessment of eosinophilic airway inflammation in asthma. Clinically relevant increases in FENO have been reported 24 h after positive specific inhalational challenge (SIC) tests in occupational asthma. We aimed to determine whether positive SICs could be discriminated from control tests, on the basis of change in FENO.

METHODS

We reviewed all positive SICs to a variety of agents performed at our institution 2008-2012 and gathered data on age, sex, asthmatic response (immediate/dual/late), smoking status, inhaled corticosteroid usage, and FENO pre- and 24-h postcontrol and positive SIC from each worker. Changes in FENO after positive SICs were compared with control SICs from each worker, by using paired Student's t tests.

RESULTS

In 16 workers, negative control challenges were associated with mean changes in FENO of 9 % (95 % CI -1.14 to 19.01) or 1.1 ppb (95 % CI -3.59 to 5.84); 2 of 16 (13 %) workers tested showed increases in FENO that were clinically relevant based on recent guidelines. Subsequent positive SICs were associated with mean changes in FENO of 7 % (95 % CI −15.73 to 29.6) or 2.1 ppb (95 % CI -6.07 to 10.19), which were not significantly different to controls; only 2 of 16 (13 %) workers had FENO changes that were clinically relevant.

CONCLUSIONS

FENO changes above the upper confidence limits of ≥20 % or ≥6 ppb may be considered to be outside the range of normality. However, the majority of workers who had clearly positive SICs to common low molecular weight agents also had no statistically or clinically relevant increase in FENO. Therefore, change in FENO does not predict a positive SIC in this group.

Assessment of public health impact of work-related asthma

Background

Asthma is among the most common chronic diseases in working-aged populations and occupational exposures are important causal agents. Our aims were to evaluate the best methods to assess occurrence, public health impact, and burden to society related to occupational or work-related asthma and to achieve comparable estimates for different populations.

Methods

We addressed three central questions: 1: What is the best method to assess the occurrence of occupational asthma? We evaluated: 1) assessment of the occurrence of occupational asthma per se, and 2) assessment of adult-onset asthma and the population attributable fractions due to specific occupational exposures. 2: What are the best methods to assess public health impact and burden to society related to occupational or work-related asthma? We evaluated methods based on assessment of excess burden of disease due to specific occupational exposures. 3: How to achieve comparable estimates for different populations? We evaluated comparability of estimates of occurrence and burden attributable to occupational asthma based on different methods.

Results

Assessment of the occurrence of occupational asthma per se can be used in countries with good coverage of the identification system for occupational asthma, i.e. countries with well-functioning occupational health services. Assessment based on adult-onset asthma and population attributable fractions due to specific occupational exposures is a good approach to estimate the occurrence of occupational asthma at the population level. For assessment of public health impact from work-related asthma we recommend assessing excess burden of disease due to specific occupational exposures, including excess incidence of asthma complemented by an assessment of disability from it. International comparability of estimates can be best achieved by methods based on population attributable fractions.

Conclusions

Public health impact assessment for occupational asthma is central in prevention and health policy planning and could be improved by purposeful development of methods for assessing health benefits from preventive actions. Registry-based methods are suitable for evaluating time-trends of occurrence at a given population but for international comparisons they face serious limitations. Assessment of excess burden of disease due to specific occupational exposure is a useful measure, when there is valid information on population exposure and attributable fractions.

Clinical assessment of occupational asthma and its differential diagnosis

Occupational asthma (OA) is defined as asthma caused by sources and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace. Two types of OA are distinguished based on their appearance after a latency period or not. The most frequent type appears after a latency period leading to sensitization; the clinical assessment of this type of OA is the topic of this review. The differential diagnosis of OA is also reviewed, including work-exacerbated asthma, eosinophilic bronchitis, hyperventilation syndrome, vocal cord dysfunction, bronchiolitis, and other causes of dyspnea or cough.

Occupational rhinitis

Work-related rhinitis, which includes work-exacerbated rhinitis and occupational rhinoconjunctivitis (OR), is two to three times more common than occupational asthma. High molecular weight proteins and low molecular weight chemicals have been implicated as causes of OR. The diagnosis of work-related rhinitis is established based on occupational history and documentation of immunoglobulin E (IgE) mediated sensitization to the causative agent if possible. Management of work-related rhinitis is similar to that of other causes of rhinitis and includes elimination or reduction of exposure to causative agents combined with pharmacotherapy. If allergens are commercially available, allergen immunotherapy can be considered.

Occupational rhinitis

Work-related rhinitis, which includes work-exacerbated rhinitis and occupational rhinitis, may be two to three times more common than occupational asthma. Both high molecular weight proteins and low molecular weight chemicals have been implicated as causes of occupational rhinitis. A diagnosis is established based on occupational history and, if appropriate, documentation of IgE-mediated sensitization to the causative agent. Management of work-related rhinitis is similar to that of non-work-related rhinitis and includes elimination or reduction of exposure to offending agents combined with pharmacotherapy. If treatment allergens are commercially available, allergen immunotherapy may also be considered if appropriate.

New-onset adult asthma in relation to damp and moldy workplaces

OBJECTIVE

Damp and moldy indoor environments aggravate pre-existing asthma. Recent meta-analyses suggest that exposure to such environments may also induce new-onset asthma. We assessed the probability of molds being the cause of asthma in a patient series examined because of respiratory symptoms in relation to workplace dampness and molds.

METHODS

Altogether 694 such patients had been clinically assessed between 1995 and 2004. According to their histories, they had all been exposed to molds at work and had suffered from work-related lower respiratory symptoms. The investigations had included specific inhalation challenge (SIC) tests with mold extracts and serial peak expiratory flow (PEF) recordings. Using internationally recommended diagnostic criteria for occupational asthma (OA), we categorized the patients into three groups: probable, possible, and unlikely OA (156, 45, and 475 patients, respectively). The clinical details of 258 patients were analyzed, and their levels of microbial exposure were evaluated.

RESULTS

The agreement between the serial PEF recordings and SIC tests (both being either positive or negative) was 56%. In the group of probable OA, mold sensitization was found in 20%. The level of exposure and sensitization to molds was associated with probable OA. At 6 months, the follow-up examinations of 136 patients with probable OA showed that the symptoms were persistent, and no improvement in spirometry was noted despite adequate treatment. Only 58% of the patients had returned to work.

CONCLUSIONS

Exposure to damp and moldy workplaces can induce new-onset adult asthma. IgE mediation is a rare mechanism, whereas other mechanisms are unknown.

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.

Leukotrienes and 8-isoprostane in exhaled breath condensate in bronchoprovocation tests with occupational allergens

Exhaled breath condensate (EBC) contains many substances, which could help in diagnosis of occupational asthma. The aim of the study is to monitor leukotrienes (LT) and 8-isoprostane from EBC in bronchoprovocation tests with allergens in 47 patients with suspected occupational asthma. Forty-one patients were tested negative. In negative bronchoprovocation tests, no significant differences (P<0.05) were seen between the five measurements during and after the test. In control measurements (without provocation), significant differences were found among four measurements done within 24h for 8-isoprostane (P=0.0138). The relationship between the log transformed ratios of the EBC parameters and FEV(1) was never significant at the 5% level in control measurements, while in negative tests, statistical significance was recorded for LTB(4) (P=0.0299) before and 5h after the test. Six of 47 patients were tested positive. Such a small number of patients did not allow proper statistical analysis and therefore, the results are described separately for each patient.

Diisocyanate conjugate and immunoassay characteristics influence detection of specific antibodies in HDI-exposed workers

BACKGROUND

The structural characteristics of diisocyanate chemical protein antigens vary depending upon the methods of production, and may influence diisocyanate antigen immunoassays. The impact of different antigen preparation methods on immunoassay sensitivity, specificity, and predictive value for identifying workers with diisocyanate asthma (DA) has not been systematically evaluated.

OBJECTIVE

Evaluate the influence of preparation methodology of hexamethylene diisocyanate human serum albumin (HDI-HSA) conjugates on the performance of specific antibody assays for identifying workers with confirmed HDI asthma.

METHODS

Asthmatic reactions to HDI exposure were assessed in 80 autobody shop workers by specific inhalation challenge (SIC). HDI-specific IgE and IgG in serum were measured by RAST and ELISA with seven different HDI-HSA conjugates prepared in liquid phase with monomeric or polymeric HDI, or vapour-phase monomeric HDI. The HDI : HSA substitution ratios were determined by mass spectrometry.

RESULTS

DA was confirmed by SIC in 23 subjects. The maximal sensitivity for detecting specific IgE among workers with positive SIC results was higher with RAST and with polymeric vs. monomeric HDI-albumin conjugates (21.7% vs. 8.7%) with a generally high specificity (>or=95%). HDI-HSA specific IgG antibody was also detected in 22-43% of HDI asthmatics depending upon the conjugate used. The specificity of specific IgG varied from 88% to 96%, and it was higher for monomeric (vs. polymeric) HDI-albumin conjugates with low (vs. high) substitution ratios.

CONCLUSION

The test performance of specific IgE and IgG immunoassays for identifying a positive SIC response varied with different HDI-HSA conjugates. Standard test antigens and common immunoassays must be used to minimize inter-laboratory variability.

Occupational asthma due to low molecular weight agents

Occupational asthma is defined as variable airflow obstruction and airways hyperresponsiveness caused by exposure to agents present in the workplace. Low molecular weight agents such as isocyanates, aldehydes, anhydrides, colophony, dyes, persulphate, amines, acrylates and metals are steadily increasing as causative agents of occupational asthma. Isocyanates, aldehydes and anhydrides my cause sensitisation through an IgE mediated response in some workers. These agents act as haptens which combine with a carrier protein to form a complete antigen. Assays for the detection of specific IgE are standardized for very few agents and have a good specificity, but poor sensitivity. The diagnosis of occupational asthma relies not only on a suggestive hystory showing that asthma is caused or exacerbated specifically by work exposure, but in most cases needs to be confirmed by objective means. Combined monitoring of lung function parameters, such as peak expiratory flow rate at the work site and non specific bronchial hyperresponsiveness during and away from exposure, is necessary. The "gold standard" for confirming a diagnosis in an individual worker still remains the specific bronchoprovocation test, which has now reached a high degree of sensitivity, specificity and reproducibility for agents such a s isocyanates. In occupation asthma due to low molecular weight agents there are no individual risk factors which could predict the susceptibility to develop the disease. The primary prevention is based on appropriate interventions tn the workplace. The strict medical surveillance of workers may allow the early diagnosis and removal from further exposure in order to prevent morbidity and disability.

Occupational asthma in apprentice adolescent car painters

Occupational asthma (OA) is one of the leading causes of pulmonary diseases and has been extensively studied in adults. Childhood employment, a significant problem in many developing countries, should be studied to determine and evaluate its effects on psychosocial and lung health. In order to investigate the presence of work-related asthma-like symptoms and OA in apprentice adolescent car painters, 72 adolescents between the ages of 15-20 yr studying in Vocational Training Centres of Ankara were investigated using questionnaire, pulmonary function test (PFT), serial peak expiratory flow (PEF) measurements and methacholine inhalation tests. As a control group, 72 adolescents studying in Industrial and Commercial Training Centres located in the same environment were investigated with questionnaire and PFT. Almost 50% of the study group had work-related asthma-like symptoms for which occupational dermatitis history was predictive [odds ratio: 2.9 (1.026-8.13) (95% confidence interval)]. Seventeen of 22 with serial PEF measurements showed a variability of > or =20% and three (4.2%) of 12 tested with methacholine inhalation test had a PC20 < or = 8 mg/ml, which led to the diagnosis of OA. There was no statistically significant difference between study and control groups in terms of PFT. In conclusion, the high prevalence of work-related asthma-like symptoms among adolescent car painters clearly indicates the need for routine follow-up of adolescent workers for lung health.

Assessment of bronchial responsiveness following exposure to inhaled occupational and environmental agents

Inhalation of a range of agents can result in airway inflammation and/or irritation. This may result in occupational asthma or reactive airways dysfunction syndrome. Reactive airways dysfunction syndrome follows a single large exposure to a chemical agent but is now frequently embraced under the wider term of irritant-induced asthma, a term that also includes asthma due to persistent, lower dose irritant exposures. Bronchial hyperresponsiveness is a hallmark of both occupational asthma and reactive airways dysfunction syndrome, although some patients with occupational asthma may occasionally have typical clinical features without increased bronchial hyperresponsiveness. Following removal of the causal agent in occupational asthma, bronchial hyperresponsiveness generally returns towards normal over a 2-year period, although some individuals demonstrate increased bronchial hyperresponsiveness for longer. Measurement of specific bronchial hyperresponsiveness to the primary causal agent in occupational asthma is used diagnostically but not for assessing prognosis. Bronchial hyperresponsiveness to inhaled methacholine can be measured across individual workshifts to assess work-related change. It may also be measured at the end of a work period when exposure has occurred, and compared with values following a period away from work. There have been no direct, systematic comparisons of changes in methacholine responsiveness in the diagnosis of occupational asthma compared with the more frequently used serial peak flow measurements. Patients with reactive airways dysfunction syndrome classically exhibit non-specific bronchial hyperresponsiveness, which can be readily measured by evaluating responses to inhaled methacholine. Bronchial hyperresponsiveness in reactive airways dysfunction syndrome can persist for many years after initial exposure and serial changes can be used to assess recovery and subsequent disability over time.

Validation of specific inhalation challenge for the diagnosis of occupational asthma due to persulphate salts

BACKGROUND

The significant value of tests used to certify the diagnosis of occupational asthma due to persulphate salts remains uncertain.

AIMS

To validate the specific inhalation challenge (SIC) test for the diagnosis of occupational asthma.

METHODS

Eight patients with occupational asthma due to persulphate salts, eight patients with bronchial asthma who were never exposed to persulphate salts, and ten healthy subjects were studied. Clinical history taking, spirometry, bronchial challenge with methacholine, skin prick testing to common inhalant allergens and persulphate salts, total IgE levels, and SIC to potassium persulphate were carried out in all subjects. The SIC used increasing concentrations of potassium persulphate (5, 10, 15, and 30 g) mixed with 150 g of lactose. Patients tipped the mixture from one tray to another at a distance of 30 cm from the face for 10 minutes in a challenge booth.

RESULTS

The SIC was positive in all subjects with persulphate induced asthma and in one patient with bronchial asthma who had never been exposed to persulphate salts. Sensitivity was 100% (95% CI 67.6 to 100) and specificity was 87.5% (95% CI 52.9-97.8) when patients with occupational asthma due to persulphate salts were compared with those with bronchial asthma never exposed to persulphate salts.

CONCLUSIONS

SIC to persulphate salts performed according to the protocol described appears to be useful for the diagnosis of occupational asthma secondary to inhalation of this substance.

Occupational asthma caused by high-molecular-weight substances

More than 250 agents that are encountered in the workplace have been shown to induce asthma in susceptible individuals. It is estimated that 2% to 15% of cases of asthma may be occupational. High-molecular-weight substances, such as plant and animal proteins, enzymes, and large carbohydrate molecules, can induce IgE-mediated occupational asthma. The incidence of disease varies among industries and is dependent on the physiochemical properties of the agent, the level and duration of exposure, industrial hygiene, engineering practices, and host factors. Risk factors, common high-molecular-weight workplace antigens, diagnosis, treatment, and prognosis are discussed.

Provocation studies in the diagnosis of occupational asthma

Specific and nonspecific provocation studies, although not always essential for diagnosing OA, help confirm the diagnosis and identify the offending agent. Nonspecific bronchial challenge testing is used to detect airway hyperresponsiveness and to clarify the nature of the patient's symptoms. Pharmacologic bronchoconstrictor agents (eg, methacholine, histamine) most commonly are used for the challenge, but nonisotonic aerosols, exercise and hyperventilation also can show airway hyperresponsiveness. Nonspecific challenges usually are done in the laboratory, but can be done at the workplace if emergency equipment is available. A comparison of results obtained at and away from the workplace (at least 1 week apart) may be helpful in diagnosing OA. Specific bronchial challenge testing is considered the gold standard for OA diagnosis. It can be crucial in helping physicians, employers, and employees make decisions about continued employment, compensation, career changes, and treatment. Testing can pinpoint new industrial agents that cause OA, enabling dissemination of information on its hazards to the public and within the industry. The nature of the agent determines the type of protocol that is used for testing. Agents can be in the form of dusts, powders, aerosols, vapors gases, and animal dander. Exposure can be as simple as having patients simulate their work activities, or as complicated as using special challenge chambers with controlled environments and precise delivery of agents. Performing control challenges with a component that is separate from the test agent is essential to avoid false-positive results. The timing, duration, and dosing of exposure depend on the type of reaction that has been experienced previously, the nature of the agent, and the patient's baseline airway hyperresponsiveness. Serial spirometry and observation often are done for up to 8 hours to monitor early and late reactions. SBC testing should be performed in the proper medical setting in which emergency equipment available and should be administered only by healthcare personnel who are trained and experienced in the procedures. Safety of the patient is the primary consideration.

Onset and Duration of Action of Ketotifen???0.025%???and???Emedastine???0.05% in Seasonal Allergic Conjunctivitis

OBJECTIVE

To compare the efficacy, onset and duration of action, and the safety of ketotifen fumarate 0.025% ophthalmic solution and emedastine difumarate 0.05% ophthalmic solution in subjects with seasonal allergic conjunctivitis (SAC) induced by allergen exposure, using the Vienna Challenge Chamber model.

DESIGN AND SETTING

This was a double-masked, randomised, comparative, crossover study conducted at an allergy outpatient clinic in Austria.

STUDY PARTICIPANTS

Subjects with an allergy to grass pollen were exposed to the allergen in a pollen chamber for 4 hours, followed by a 3-hour break and then a second exposure for 3 hours.

INTERVENTIONS

Study participants were randomised to a treatment sequence (ketotifen followed by emedastine or emedastine followed by ketotifen), receiving 1 drop per eye of ketotifen or emedastine 2 hours after the initial allergen exposure in the pollen chamber.

OUTCOMES

Individual and composite ocular, individual and composite nasal, and total (ocular + nasal) symptom complex scores were determined by repeated exposure to allergen 0-2 hours and 5-8 hours after dosing. Onset of action was defined as the time to the first observation of a 20% reduction from baseline in the composite ocular symptom score.

RESULTS

All 37 subjects enrolled completed the study. The median time to onset of action was 15 minutes for ketotifen and 30 minutes for emedastine. This difference was significant using the generalised linear model (p = 0.048), but not for the log-rank test analysis. In the initial 2 hours post dose, ketotifen provided significantly greater relief of both composite ocular symptoms (p = 0.026) and total symptom complex (p = 0.014). Both medications were effective in reducing symptoms 5 to 8 hours after dosing. No adverse events were reported for either treatment.

CONCLUSIONS

In the Vienna Challenge Chamber model, ketotifen and emedastine both effectively alleviated ocular symptoms of SAC after single-dose administration. Ketotifen had a faster onset of action and provided better symptom relief than emedastine during the first 2 hours after dosing. The rapid onset of action and symptom control make ketotifen a valuable treatment for SAC.

Agricultural lung disease

Agricultural work is associated with high rates of injury, disability, and illness. Agricultural workers are at increased risk for a variety of illnesses including respiratory disorders, dermatologic conditions, and cancer. The recognition of ODTS led to increased understanding of acute illness in farmers and grain workers. Previously, many cases of acute illness were probably erroneously called farmer's lung. The same agents that are responsible for ODTS are responsible for the high prevalence of bronchitis in certain agricultural workers. The recent description of the innate immune system is very exciting because it will lead to increased understanding of the pathogenesis of organic dust induced disorders.

[Sensitization and occupational asthma in poultry workers]

BACKGROUND

A high prevalence of asthma has been reported in poultry farmers. Our aim was to determine air contaminants in poultry confinement buildings and the prevalence of occupational asthma in these workers.

PATIENTS AND METHOD

Spanish poultry farmers who participated in the European Study Prevalence and Risk Factors for Airway Obstruction in Farmers, who worked inside confinement buildings, were enrolled in a cross-sectional study that included the measurement of air contaminants (ammonia, total dust, endotoxin and microorganisms), symptoms, skin testing with common and poultry-related allergens, and a specific bronchial challenge. The Spearman correlation coefficient was used to assess the correlation between air contaminants.

RESULTS

14/15 poultry farmers participated in the study (response index: 93.3%). Concentrations of air contaminants in the confinement buildings [median (interquartile range)] were: 7.5 (5-20) ppm for ammonia, 2.6 (1.8-4.6) mg/m3 for total dust, 137.1 (58.6-243.9) ng/m3 for endotoxin and 7,600 (907-27,750) colony-forming units/m3 * 103 for bacteria. Endotoxin correlated with bacterial concentration (r = 0.69, p < 0.01). 5/14 poultry farmers reported wheezing and/or asthma within the last year (35.7%), and in 2 of them spirometry demonstrated current asthma (14.3%). Specific bronchial provocation confirmed the diagnosis of occupational asthma in one subject with current asthma sensitized to the storage mite Lepidoglyphos destructor (7.1%).

CONCLUSIONS

One third of poultry farmers working inside confinement buildings reported wheezing, that is partly attributable to occupational asthma caused by storage mites.

Occupational asthma in symptomatic workers exposed to natural rubber latex: evaluation of diagnostic procedures

BACKGROUND

Natural rubber latex (NRL) has been increasingly identified as a cause of occupational asthma (OA).

OBJECTIVE

We sought to examine the accuracy of the clinical history, immunologic tests, and assessment of nonspecific bronchial hyperresponsiveness in diagnosing OA caused by latex compared with that of the specific inhalation challenge (SIC).

METHODS

Forty-five consecutive patients referred for investigation of possible OA caused by latex underwent a diagnostic protocol, including an open medical questionnaire, skin prick testing against latex, measurement of bronchial responsiveness to histamine, and inhalation challenge with latex gloves. Recorded clinical history was judged retrospectively by 4 physicians who were blinded for the results of other objective tests.

RESULTS

The clinical history, skin prick testing against NRL, and assessment of nonspecific bronchial hyperresponsiveness showed a high sensitivity (87%, 100%, and 90%, respectively) but a low specificity (14%, 21%, and 7%, respectively) when compared with the results of the SIC. Logistic regression analysis showed that combining the results of skin prick tests against latex with the clinical history enhanced the negative predictive value from 50% to 71%, whereas the positive predictive value remained virtually unchanged (75% vs 76%).

CONCLUSION

The clinical history and immunologic tests were the most useful procedures in diagnosing NRL-induced asthma, although combining the 2 procedures remained less accurate than SIC. Further examination of the predictive values of available tests is warranted to recommend diagnostic strategies that are specific to the various agents causing OA.

Development of an expert system for the interpretation of serial peak expiratory flow measurements in the diagnosis of occupational asthma. Midlands Thoracic Society Research Group

If asthma is due to work exposures there must be a relation between these exposures and the asthma. Asthma causes airway hyperresponsiveness and obstruction; the obstruction can be measured with portable meters, which usually measure peak expiratory flow, or sometimes forced expiratory volume in 1 second (FEV1). These can be measured serially (for instance 2 hourly) over several weeks at and away from work. Once occupational asthma develops, the asthma will be induced by many non-specific triggers common to non-occupational asthma. The challenge is to identify changes in peak expiratory flow due to work among other non-occupational causes. Standard statistical tests have been found to be insensitive or non-specific, principally because of the variable period for deterioration to occur after exposure, and the sometimes prolonged time for recovery to occur, such that days away from work may initially have lower measurements than days at work. A computer assisted diagnostic aid (Oasys) has been developed to separate occupational from non-occupational causes of airflow obstruction. Oasys-2 is based on a discriminant analysis, and achieved a sensitivity of 75% and a specificity of at least 94%; therefore peak expiratory flow monitoring combined with Oasys-2 analysis is better to confirm than to exclude occupational asthma. A neural network version in development has improved on this. Both have been based on expert interpretation of peak flow measurements plotted as daily maximum, mean, and minimum, with the first reading at work taken as the first reading of the day. Oasys has been evaluated with independent criteria against measurements made in a wide range of occupational situations. Oasys is sufficiently developed to be the initial method for the confirmation, although less so for exclusion of occupational asthma.

Current diagnostic methods for diisocyanate induced occupational asthma

BACKGROUND

Diisocyanates are among the most frequent causes of occupational asthma in industrialized countries. Early diagnosis of diisocyanate asthma followed by prompt termination of chemical exposure can prevent chronic morbidity due to persistent asthma. The accurate diagnosis of diisocyanate asthma requires a systematic approach that combines information obtained from the occupational history, immunologic tests and physiologic studies.

METHODS

The advantages, limitations and validity of various methods and diagnostic guidelines utilized in the evaluation of diisocyanate asthma are reviewed.

RESULTS

Recommended methods for evaluation of diisocyanates asthma are similar to approaches for other causative agents. Serologic assays of specific IgE are specific but insensitive diagnostic markers of diisocyanate asthma. If possible, workers should be evaluated, while at work, in order to demonstrate work-related changes in lung function associated with diisocyanate exposures. Specific bronchoprovocation challenge testing with diisocyanates, is reserved for situations where the diagnosis cannot be confirmed at work. Such tests can be performed safely but should be conducted exclusively at specialized centers by experienced personnel.

CONCLUSIONS

Published diagnostic guidelines for occupational asthma are directly applicable to the evaluation of diisocyanate asthma.

Occupational respiratory hypersensitivity caused by preparations containing acrylates in dental personnel

BACKGROUND

Allergic contact dermatitis caused by acrylate compounds is common in dental personnel; they also often complain of work-related respiratory or conjunctival symptoms.

OBJECTIVE

The aim of the present study was to report the cases of acrylates induced respiratory hypersensitivity in dental personnel diagnosed in Finland during the last 6 years.

METHODS

Occupational asthma, rhinitis, laryngitis and pharyngitis cases were diagnosed according to patient history, PEF monitoring, and a work-simulating provocation test.

RESULTS

Twelve cases of respiratory hypersensitivity caused by acrylates diagnosed in dental personnel (six dentists and six dental nurses) in 1992-97 are reported. During this period one case of conjunctivitis and one of laryngitis have been published separately. Nine cases of occupational asthma, two rhinitis cases, and one laryngitis case were verified according to the challenge tests with dental acrylate compounds (acrylates, methacrylates and epoxy acrylates). Only three patients had positive skin-prick test reactions to common environmental allergens, and none reacted to acrylates in the skin-prick tests. Five patients had an elevated total IgE (>110 kU/L). PEF follow-up showed an occupational effect in all examined eight patients with diagnosed asthma. The mean duration of exposure to acrylates was 22 years, and the duration of respiratory symptoms 8 years.

CONCLUSIONS

The results indicate that acrylates constitute an important hazard for dental workers. The mechanism of respiratory hypersensitivity is still unknown, and it is probably not IgE-mediated.

Efficacy and safety relative to placebo of an oral formulation of cetirizine and sustained-release pseudoephedrine in the management of nasal congestion

BACKGROUND

The aim of this study was to assess the clinical efficacy of an oral formulation of cetirizine 5 mg with sustained-release pseudoephedrine (PSE) 120 mg relative to placebo in patients with nasal congestion.

METHODS

Twenty-four patients with perennial rhinitis due to house-dust-mite (HDM) allergy were recruited in this crossover study. A treatment period of 1 week, in which cetirizine/PSE was administered twice daily, was followed by a washout period of at least 2 weeks and a further period of 1 week in which the alternative treatment was given to each patient. Immediately after the first dose of each medication (day 1), nasal congestion and related symptoms were assessed during a 7-h challenge with HDM feces, with the Vienna Challenge Chamber (VCC), to investigate onset of action of the preparation. A second challenge of 3-h duration, carried out at least 12 h after the final dose, was undertaken after 1 week (mean) of twice-daily treatment to assess residual effects of the formulation after achievement of steady state.

RESULTS

The oral formulation of cetirizine/PSE was significantly (P<0.001) superior to placebo in improving nasal obstruction during both challenges. The improvement in nasal airflow and nasal patency was significantly greater with cetirizine/PSE than with placebo (P<0.02). In addition, subjective assessment of nasal symptoms showed that cetirizine/PSE was significantly superior to placebo in both challenges for the sum of nasal obstruction scores (P<0.01). Both medications were well tolerated, and no serious adverse events occurred during the study.

CONCLUSIONS

In this study, cetirizine/PSE relieved nasal congestion and other objective and subjective symptoms to a significantly greater extent than placebo. No serious adverse events occurred, and both regimens were equally well tolerated.

[The specific bronchial provocation test in the diagnosis of occupational asthma]

Specific bronchial challenge (SBC) testing is a key technique for diagnosing the origin of occupational asthma (OA). SBC is indicated in specific circumstances, including whenever several agents present in the work environment may be the cause of OA, when new or unusual occupational agents need to be identified, when evidence for legal action is required, or when research is conducted. SBC procedures are not standardized, because of the great diversity of occupational agents and the variety of physical and chemical properties involved. Thus, SBC testing with agents found in fumes, gases or vapors can be administered in special cabins or in closed circuits with continuous monitoring of sub-irritant concentrations. Agents found in dust, most but not all of which have high molecular weights, may be appropriate for routine SBC testing in an allergy laboratory. This paper will treat only these cases. SBC must be formed in specialized centers by experienced personnel, as it is a sophisticated and potentially dangerous technique. We describe a series of 20 patients diagnosed of OA in our unit over the past two years in whom SBC provided an etiologic diagnosis. All were exposed to dust or aerosols at work. The cause was a substance of high molecular weight in 17 cases, and low molecular weight in 3. The procedure used is described and models of bronchial response are discussed.

Bronchial responsiveness to ultrasonic "fog" in occupational asthma due to low molecular weight chemicals

BACKGROUND

In a previous work we have demonstrated that the use of an indirect stimulus such as ultrasonically nebulized distilled water (UNDW, "fog") challenge, in addition to methacholine, in the assessment of occupational asthma due to TDI improves our ability in detecting sensitized subjects.

OBJECTIVE

In the present study we aimed to determine the validity of "fog" in the assessment of occupational asthma induced by various low molecular weight substances.

METHODS

Fourty subjects exposed to low molecular weight substances with work-related respiratory symptoms underwent methacholine, UNDW and specific bronchial challenge tests. Diagnosis of occupational asthma was made in 20 of 40 patients who developed bronchoconstrictive responses to the specific challenges (reactors). Sensitivity and specificity of UNDW alone, of methacholine alone, and of the combination of the two tests were determined at two different cutpoints of PD20FEV1 of methacholine, with the results of the specific challenge as the "gold standard".

RESULTS

Frequency and severity of bronchial hyperresponsiveness both to UNDW and to methacholine were significantly higher in reactors than in nonreactors. Ultrasonically nebulized distilled water had higher specificity (80% versus 60%) but lower sensitivity (65% versus 75% to 90%) than methacholine. As compared with methacholine alone, the combination in series of the two challenges (both challenges positive) substantially improved specificity (85% versus 60%).

CONCLUSIONS

In conclusion, in the assessment of low molecular weight chemical-induced asthma diagnosed with the specific challenge as the "gold standard," UNDW challenge proves more specific than methacholine for occupational asthma, but it is considerably less sensitive. The combination of the two challenges results in very high sensitivity and high specificity for occupational asthma, therefore, although further investigations are required for the definitive diagnosis, it should be regarded as a useful means to confirm objectively a suggestive history.

Pocket-sized spirometer for monitoring bronchial challenge procedures

Diagnosis of occupational asthma is verified by inhalation challenge testing when frequent monitoring of peak expiratory flow (PEF) or forced expiratory volume in 1 s (FEV1) is needed. FEV1 measurements also allow frequent monitoring of changes in small airways. For the follow-up of lung function of suspected occupational asthma, a reliable, personal and mobile device is needed. We studied the accuracy of a pocket-sized spirometer, Micro Plus Spirometer (MP), compared with our former combination of two devices, i.e. the values of forced expiratory volume in 1 s (FEV1) with those measured with the Vitalograph bellow spirometer (V); and the peak expiratory flow (PEF) values with the values obtained with a Wright PEF meter (W). In healthy control subjects, the values of FEV1 obtained with Micro Plus correspond well to those obtained using a bellow spirometer (R = 0.97) and the mean difference (MP-V) was -0.06 1 irrespective of the mean FEV1 value. W gives smaller PEF values than the MP; the mean difference in PEF (MP-W) was 44 1 min-1, but the values increased linearly with increasing flow. The poor relation between PEF values might be based on the low reliability of the Wright device. In patient follow-up, the FEV1 values measured with MP and V showed a good correlation (R = 0.99). The PEF values in patients increase linearly measured with W vs. MP with increasing flow values. In conclusion, we found the pocket-sized spirometer a handy and useful device for monitoring bronchial challenge procedures in patients with suspected occupational asthma. The number of exhalations during the challenge test follow-up is lessened when FEV1 and peak expiratory flow (PEF) can be measured simultaneously.

Closed-circuit apparatus for specific inhalation challenges with an occupational agent, formaldehyde, in vapor form

Specific inhalation challenges are an important tool for confirming occupational asthma. In recent years, we have described two closed-circuit apparatuses that allow exposure to stable and controlled concentrations of particles and isocyanate gases. More recently, we developed a similar apparatus that generates chemicals in vapor form. The aim of this work is to describe its performance in the specific case of formaldehyde. This instrument is made of four parts: a generator as such, an exposure chamber, a monitor, and an automated regulatory system. This apparatus was assessed in four subjects suspected of having formaldehyde-induced asthma or alveolitis. The concentrations of formaldehyde were increased from 0.5 to 1 mg/m3 to 3 mg/m3 keeping the concentration at a value of 3 mg/m3 or less (threshold limit value). The dispersion of obtained values by comparison with the median data (6 values) was as follows: maximum value, 12 to 84%; minimum value, 20 to 58%; interquartile range, 0.13 to 0.9 mg/m3. We observed that target concentrations took a few minutes to be reached, but, once they were obtained, delivered concentrations were stable. The new vapor-delivery apparatus allows us to obtain concentrations of formaldehyde that are close to target concentrations with an acceptable dispersion of values around target concentration. Its use should be extended to other chemicals besides formaldehyde.

Increase in non-specific bronchial hyperresponsiveness as an early marker of bronchial response to occupational agents during specific inhalation challenges

BACKGROUND

Specific bronchial reactivity to occupational agents may decline after exposure in the workplace ceases leading to falsely negative specific inhalation challenges. A study was carried out to assess prospectively whether increases in nonspecific bronchial hyperresponsiveness could be useful in detecting the bronchial response to occupational agents during specific inhalation challenges.

METHODS

Specific inhalation challenges were performed in 66 subjects with possible occupational asthma due to various agents. After a control day the subjects were challenged with the suspected agent for up to two hours on the first test day. Those subjects who did not show an asthmatic reaction were rechallenged on the next day for 2-3 hours. The provocative concentration of histamine causing a 20% fall (PC20) in the forced expiratory volume in one second (FEV1) was assessed at the end of the control day as well as six hours after each challenge that did not cause a > or = 20% fall in FEV1. The subjects who had a significant (> or = 3.1-fold) reduction in PC20 value at the end of the second challenge day were requested to perform additional specific inhalation challenges.

RESULTS

The first test day elicited an asthmatic reaction in 25 subjects. Of the other 41 subjects five (12%, 95% confidence interval (CI) 4% to 26%) exhibited a > or = 3.1-fold fall in the PC20 value after the inhalation challenge and developed an asthmatic reaction during the second (n = 3) or third (n = 2) challenge exposure. The offending agents included persulphate (n = 1), wood dust (n = 2), isocyanate (n = 1), or amoxycillin (n = 1). These five subjects had left their workplace for a longer period (mean (SD) 21 (14) months) than those who reacted after the first specific inhalation challenge (8 (11) months).

CONCLUSIONS

The increase in non-specific bronchial hyperresponsiveness after a specific inhalation challenge can be an early and sensitive marker of bronchial response to occupational agents, especially in subjects removed from workplace exposure for a long time. Non-specific bronchial hyperresponsiveness should be systematically assessed after specific inhalation challenges in the absence of changes in airway calibre.

Exposure chamber for allergen challenge. The development and validation of a new concept

Exposure chambers have proven to be valuable tools in studying allergic diseases. The chamber provides a controlled environment and maintains conditions for measuring the amount of allergen inducing symptoms in allergic subjects. The aim of the present study was to develop and test an exposure chamber. The chamber was constructed as an airtight tent, made of transparent polyethylene, easy to adapt to the shape of an existing room, easy to clean, and providing exact allergen-dosage control. Airflow to the interior of the tent was controlled by a variable inlet ventilator fitted with a micropore filter and balanced by a variable high-volume air-sampler on the outlet side. Trace material and allergen were administered as aerosols with a nebulizer connected to the inlet pipe. Samples were obtained from interior surfaces and filters at the outlet. Two different methods were used to test the concept. One method used a colored, neutral trace substance (phenol red indicator) measured photometrically on extracts from filters. Secondly, house-dust mite allergen (Dermatophagoides pteronyssinus) was applied, with samples analyzed by an ELISA technique. The results demonstrated the ability of the system to administer and sample allergen with a high degree of reproducibility. A clinical pilot trial proved the capability of the system to initiate symptoms in allergic subjects.

Occupational respiratory and skin sensitization caused by polyfunctional aziridine hardener

Polyfunctional aziridine (PFA) is increasingly used as a water-based crosslinker in two-component paints, paint primers, lacquers, topcoats and other protective coatings. The crosslinker is made by reacting multifunctional acrylic monomer with a highly reactive aziridine compound. Respiratory allergy or hypersensitivity from PFA has not been reported previously. During 1978-1991 we came across nine cases with hypersensitivity from PFA: two had allergic contact dermatitis (ACD), four had occupational asthma and three had both of them. Five of the patients were parquet layers, two were fibreboard painters, one was a spray painter and one was a salesman of PFA products. ACD was diagnosed by positive allergic patch test reactions with PFA in a dilution series in petrolatum: 0.32%-0.5% gave a 2(+)-3+ allergic reaction in the five cases with ACD but 0.1% gave only a weak reaction in one case, whereas the methacrylate patch test series was negative. The diagnosis of seven cases of occupational asthma due to PFA hardener was based on symptoms related to exposure to PFA hardener at work, and on positive provocation tests with PFA hardener. One had an immediate type reaction, one a had a dual reaction, and the others had late reactions. The positive reactions with the PFA hardener and the negative reactions with the acrylate compounds indicate that PFA caused ACD which is different from the previous reports in which acrylates present as impurities in the PFA hardener caused the sensitization.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal asthma caused by airborne Platanus pollen

This work describes three patients suffering from bronchial asthma after being naturally exposed to airborne plane-tree pollen. The three patients gave immediate response in skin tests and dual response in bronchial provocations using Platanus hybrida extract. There was specific seric IgE activity against this/these antigen(s) with the CAP system. The three patients also showed significant correlation (P < 0.001) between their rhinitis and asthma symptom-scores registered on their diary cards and plane-tree pollen counts, collected using the Burkard spore trap. Among 187 patients living in Madrid and who came to our centre with a history of rhinitis and/or seasonal asthma, we found a prevalence of positive skin-prick tests to Platanus of 56%, only surpassed by gramineous pollen (Dactylis glomerata and/or Trisetum paniceum) 92% and Olea europaea 63%. The aerobiological sampling of the pollen content of the air in Madrid, carried out between 1 January 1979 and 31 December 1993 revealed an airborne presence (per cent of total yearly pollen count, mean of 1979-1993) of 14.9% for the Platanus, 14.8% for grasses, 9.8% for Olea and 3.6% for Plantago. The Platanus is one of the most frequently found pollens in the atmosphere over Madrid. At present, in this geographical area, a high percentage of patients with pollinosis are sensitive to this pollen. At least in some of these patients Platanus pollen is capable of inducing rhinitis and bronchial asthma.

Cobalt-related asthma: clinical and immunological aspects

Several clinical and experimental findings point to cobalt as the only sensitizer and causal agent of hard metal asthma. The clinical features have been clearly defined by bronchial provocation tests, with a prevalence of late phase responses. Epidemiology is still insufficient to configure prevalence and incidence rates for cobalt asthma. IgE and IgG antibodies with cobalt specificity have been demonstrated, but T-lymphocytes and eosinophils involvement seem to be important in the mechanism of an allergic inflammation in the airways. Such an immunological pathogenesis links cobalt asthma with other manifestation of hard metal disease.

Baker's asthma related to soybean lecithin exposure

We report two cases of soybean-lecithin-induced asthma in bakers. The patients experienced clinical symptoms in relation to an occupational exposure to this additive. Skin tests were positive with soybean lecithin, RAST showed a sensitization to soybean, and bronchial challenge tests were positive for a dilution of 10(-3) with this allergen. The same tests remained negative among healthy and asthmatic controls. Soybean lecithin, a common additive in bakery, must be added to the list of numerous aeroallergens involved in baker's asthma.

Usefulness of repeated measurements of bronchial hyperresponsiveness for the diagnosis of occupational asthma

To assess the usefulness of repeated measurements of nonspecific bronchial hyperresponsiveness (BHR) in the diagnosis of occupational asthma, we studied 26 consecutive patients referred to the Clinic of Occupational Medicine in Copenhagen because of suspected occupational asthma. The diagnosis of bronchial asthma was confirmed in all patients; however, 4 patients were excluded from the study as they had a baseline PC20 FEV1 histamine > 8 mg/ml. A bronchial challenge test with histamine was performed after nonspecific exposure at the workplace and after a specific bronchoprovocation test in the laboratory; substantial increase in BHR (BHRwork and BHRlab, respectively) was defined as a change in PC20 of at least one doubling concentration. A fall in FEV, of at least 20% from baseline after the specific bronchoprovocation test was defined as a positive response (SBPpos). Six patients had BHRwork and 7 patients had BHRlab; 2 patients had both BHRwork and BHRlab. Five patients had SBPpos, of whom 1 had BHRwork and 1 had BHRlab. None of the patients had three positive tests, i.e., BHRwork, BHRlab, and SBPpos. In 3 patients the specific challenge test caused a pronounced decline of lung function and deterioration in the clinical condition. With the results of the specific challenge test as the gold standard, serial measurement of histamine responsiveness may not appear to be a sensitive diagnostic test for occupational asthma. However, the high number of patients with an increase in BHR after specific and/or nonspecific occupational exposure strongly suggests that changes in bronchial responsiveness may identify patients with respiratory symptoms causally related to occupational exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchial responsiveness to ultrasonic fog in occupational asthma due to toluene diisocyanate

To determine the validity of ultrasonic nebulization of distilled water (UNDW, "fog") in comparison with methacholine challenge, in the assessment of toluene diisocyanate (TDI) asthma, we evaluated 75 subjects exposed to TDI with work-related respiratory symptoms. Subjects were submitted to bronchial challenge with methacholine at first, thereafter to UNDW inhalation and to specific challenge with TDI. The diagnosis of TDI-asthma was made in 30 of 75 patients (40 percent) who developed a bronchoconstrictive response to the specific challenge (reactors). Sensitivity and specificity of UNDW alone, methacholine alone, and of the combination of the two tests were determined with the results of the specific challenge with TDI as the "gold standard." Both frequency and severity of bronchoconstrictive response to UNDW (FEV1 decrease > or = 15 percent) and the degree (PD15 FEV1) and frequency of bronchial hyperresponsiveness to methacholine were significantly higher in TDI reactors than in nonreactors. The UNDW had higher specificity (82.2 percent vs 51.1 percent) but lower sensitivity (40 percent vs 76.7 percent) than methacholine. The combination in parallel (positivity of any of the two challenges) of methacholine and UNDW challenge did not change sensitivity to a great extent (80 percent vs 76.7 percent), whereas combination in series (positivity of both challenges) had considerably greater specificity (86.7 percent vs 51.1 percent) than methacholine alone. We conclude that in the assessment of TDI-asthma, the validity of UNDW challenge alone is limited since it is insufficiently sensitive. Instead, combining UNDW and methacholine challenge when methacholine is positive improves our ability in identifying subjects with TDI-asthma diagnosed with the specific challenge. This procedure constitutes a first objective confirmation of a suggestive history of TDI-asthma that is useful for clinical purposes. However, especially for medicolegal purposes, the definitive diagnosis requires the specific challenge.

Occupational asthma and extrinsic alveolitis due to isocyanates: current status and perspectives

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Hypersensitivity pneumonitis-like reaction among workers exposed to diphenylmethane [correction to piphenylmethane] diisocyanate (MDI)

Isocyanates are well documented as a cause of occupational asthma. A hypersensitivity pneumonitis type of reaction has also been reported but only in a few isolated cases. We investigated nine subjects who complained of respiratory and general symptoms related to workplace exposure. All the subjects had worked in a plant where a resin based on diphenylmethane diisocyanate (MDI) is used in the manufacture of woodchip boards. They underwent inhalation challenges using the MDI resin for progressively increasing periods of time on separate days. In eight subjects, exposure to subirritant amounts of MDI induced a pattern of reaction consistent with hypersensitivity pneumonitis, i.e., significant falls in both FEV1 and FVC associated with a rise in body temperature (> 38 degrees C) and an increase in blood neutrophils (> +2,500/mm3). Bronchoalveolar lavage, performed in two subjects 24 h after the end of challenge exposure, revealed an increase in lymphocytes and neutrophils. Specific immunoglobulin G (IgG) and IgE antibodies to MDI human serum albumin (HSA) conjugates were present in all subjects. We conclude that the MDI resin caused an hypersensitivity pneumonitis type of reaction in at least eight (4.7%) of the 167 potentially exposed workers employed in the plant. These findings indicate that in some workplaces, a hypersensitivity pneumonitis type of reaction may be a more frequent consequence of isocyanate exposure than is usually thought.