Diagnostic testing in occupational asthma

Assessing and treating work-related asthma

Work-related asthma is asthma that is caused or exacerbated by exposures at work. It is the most common form of occupational lung disease in developed countries. It has important impacts on the health and well-being of the affected individual, as well as consequences for society because of unemployment issues and workers' compensation claims. With ongoing exposure, occupational asthma can result in persistent airway hyperresponsiveness and, possibly, permanent disability for the individual. Thus, it is important for the clinician to be able to diagnose this disorder as quickly and accurately as possible. The evaluation of a patient with work-related asthma can be extensive. It includes obtaining a consistent history, identifying the cause in the workplace, and confirming the diagnosis with objective tests. After a diagnosis has been made, treatment must sometimes go beyond the medications used for nonoccupational asthma and include interventions to minimize or completely remove the individual from exposure to the causal agent if he or she has sensitizer-induced occupational asthma. In addition, once an individual has been identified with occupational asthma, steps should be taken to prevent the development of this disorder in other workers. The purpose of this article is to review the current literature and provide the clinician with a stepwise approach to the diagnosis and management of a patient with work-related asthma.

Peak expiratory flow is not a quality indicator for spirometry: peak expiratory flow variability and FEV1 are poorly correlated in an elderly population

BACKGROUND

Peak forced expiratory flow (PEF) and FEV(1) are spirometry measures used in diagnosing and monitoring lung diseases. We tested the premise that within-test variability in PEF is associated with corresponding variability in FEV(1) during a single test session.

METHODS

A total of 2,464 healthy adults from the Health, Aging, and Body Composition Study whose spirometry results met American Thoracic Society acceptability criteria were screened and analyzed. The three "best" test results (highest sum of FVC and FEV(1)) were selected for each subject. For those with acceptable spirometry results, two groups were created: group 1, normal FEV(1)/FVC ratio; group 2, reduced FEV(1)/FVC ratio. For each subject, the difference between the highest and lowest PEF (DeltaPEF) and the associated difference between the highest and lowest FEV(1) (DeltaFEV(1)) were calculated. Regression analysis was performed using the largest PEF and best FEV(1), and the percentage of DeltaPEF (%DeltaPEF) and percentage of DeltaFEV(1) (%DeltaFEV(1)) were calculated in both groups.

RESULTS

Regression analysis for group 1 and group 2 showed an insignificant association between %DeltaPEF and %DeltaFEV(1) (r(2) = 0.0001, p = 0.59, and r(2) = 0.040, p = 0.15, respectively). For both groups, a 29% DeltaPEF was associated with a 1% DeltaFEV(1).

CONCLUSION

Within a single spirometry test session, %DeltaPEF and %DeltaFEV(1) contain independent information. PEF has a higher degree of intrinsic variability than FEV(1). Changes in PEF do not have a significant effect on FEV(1). Spirometry maneuvers should not be excluded based on peak flow variability.

Use of objective testing in the diagnosis of work-related asthma by physician specialty

BACKGROUND

Although early and accurate diagnosis of work-related asthma is critical to avoid unnecessary medical, legal, social, and economic consequences, little is currently known about the diagnostic practices of physicians treating workers with work-related asthma.

OBJECTIVE

To characterize the use of objective diagnostic testing for work-related asthma by physician specialty.

METHODS

A cross-sectional, descriptive, comparative evaluation was conducted of 301 workers' compensation claimants with work-related asthma.

RESULTS

A few claimants (36.9%) were treated by specialists in work-related asthma (allergists, pulmonologists, or occupational medicine physicians) either initially or through the course of their claim. Workers with occupational asthma were more likely to have seen a specialist than those with work-aggravated asthma (47.9% vs 23.0%; P < .001). Less than half of the claimants with work-related asthma (43.2%) had received an objective evaluation of pulmonary function, through either pulmonary function testing or testing for reversible airflow limitation, for the evaluation of their work-related asthma. Claimants treated by specialists were significantly more likely to have received diagnostic testing during evaluation of their disease than those treated solely by generalists (82.9% vs 20.0%; P < .001).

CONCLUSIONS

The results of this study point to the lack of appropriate diagnostic care received by workers with work-related asthma. Physicians who may have questions about diagnostic procedures should consider referral to a specialist. The development of referral networks for work-related asthma may be warranted and should be explored.

The effects of long-term occupational exposure to dust from herbs

INTRODUCTION

Herbs are a heterogeneous group of many species with several thousand plants, which are used in large quantities in the pharmaceutical and food industries. The aim of the study was to analyse the health effects of long-term occupational exposure to dust from herbs.

METHODS

A group of 150 people occupationally exposed to dust from herbs, consisting of farmers and workers from herbs processing industry, was examined. As a reference group, 50 urban dwellers not exposed to any kind of organic dust were examined. Examined people were interviewed with the help of the ATS questionnaire compiled by Ferris and by the questionnaire developed in the Institute of Agricultural Medicine in Lublin, Poland for examination of work-related symptoms caused by organic dust. The lung function examination (vital capacity (VC), forced expiratory volume in the first second (FEV(1)), and FEV(1)/VC (%) of normal ranges) and allergological tests (skin prick test, precipitin test and inhibition of leukocyte migration (MIF) test) with microbial antigens were conducted.

RESULTS

71.3% (95% CI 64.1-78.6%) of the exposed people reported occurrence of work-related symptoms. A post-shift decrease of spirometric values (VC, VC%) was observed in the exposed group (mean decrease 2.6%, P<0.01). A significant relationship was found between the number of work-related symptoms and decrease of FEV(1) values, both before (Spearman correlation coefficient r=-0.21, P<0.05) and after work (r=-0.31, P<0.01). In allergological tests, the frequencies of positive reactions in the exposed group were significantly higher than in the reference group. Precipitins specific to Pantoea agglomerans were found in 30.6% (95% CI 23.2-38.1%) of exposed, compared to 12.0% among unexposed (P=0.01). The frequency of positive results in the migration inhibition test was significantly higher among exposed workers for all antigens tested.

CONCLUSION

Long-term exposure to dust from herbs causes work-related symptoms and decrease of lung function parameters, which, finally, may lead to occupational disease.

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.

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.

8. Occupational asthma and allergies

A diversity of airborne dusts, gases, fumes, and vapors can cause dose-related symptoms in individuals exposed in the workplace. More than 250 chemicals have been incriminated as a cause of occupational asthma (OA). The prevalence of OA ranges from 2% to 6% of the asthmatic population. Predisposing factors facilitating the development of OA include the work environment, climatic conditions, genetic proclivities, tobacco and recreational drug use, respiratory infection, and bronchial hyperresponsiveness. Pathogenetically, new-onset OA may be immunologic or nonimmunologic in origin. The immunologic variants are usually caused by high molecular-weight allergens such as grain dust and animal or fish protein. Symptoms ensue after a latent period of months to years. Nonimmunologic OA can be precipitated by a brief, high-level exposure to a potent irritant. Symptoms occur immediately or within a few hours of the exposure. In either instance, once the diagnosis is established, the worker should be removed from the workplace. If the diagnosis is made in a timely fashion, most workers experience improvement. Prevention is the best therapeutic intervention.

Threshold levels of purified natural Bos d 2 for inducing bronchial airway response in asthmatic patients

BACKGROUND

Provocation tests are invaluable in establishing threshold levels and a causal relationship between atopic asthma and a certain allergen source, especially in relation to work-associated exposure. Purified major allergens open possibilities for a more accurate assessment of sensitization.

OBJECTIVE

To determine the threshold dose of purified major bovine dander allergen Bos d 2 in bronchial provocation in comparison with the standard allergen and a set of other parameters of allergy.

METHOD

Nine consecutive patients referred to hospital for confirming the bovine origin of their occupational asthma were subjected to bronchial provocation tests with purified natural Bos d 2 and a standard bovine dander allergen. Additional tests included bronchial histamine challenge, measurements of total IgE, specific IgE antibody determinations and skin prick tests (SPT) with both allergens.

RESULTS

In the provocation tests with Bos d 2, a 15% decrease in the forced expiratory volume in 1 s (FEV1) and/or peak expiratory flow (PEF) values in eight out of nine patients confirmed the predominant role of Bos d 2 in the sensitization. The threshold dose of Bos d 2 varied from 0.1 microg to > 100 microg (median +/- median absolute deviation = 4.5 +/- 3.9 microg). A positive SPT was induced by a median dose of 13.9 +/- 9.8 microg of Bos d 2. Bronchial response to histamine and IgE antibodies against Bos d 2 showed the highest correlations to the provocations results.

CONCLUSIONS

The efficacy of Bos d 2 in bronchial provocation in patients with occupational cattle-associated asthma was confirmed and the range of the threshold level was determined. There were individual variations, but the response in provocation remains the reference method for identification of the cause of occupational atopic asthma. SPT and the measurement of specific IgE antibodies, preferably with purified or recombinant major allergens, increase the accuracy of the diagnosis.