What to know
State health departments in jurisdictions where work-related asthma (WRA) is reportable should encourage health-care professionals to report all diagnosed or suspected cases of asthma caused by or exacerbated by workplace exposures or conditions. Cases should include asthma caused by sensitizers or irritants and of reactive airways dysfunction syndrome (RADS).
Surveillance case definition for WRA
Surveillance case definition for WRA include both of the following:
- Healthcare professional’s diagnosis consistent with asthma.1
- An association between symptoms of asthma and work.2
The primary physiologic manifestation of airways hyperresponsiveness is variable or reversible airflow obstruction. It is commonly demonstrated by significant changes in forced expiratory volume in 1 second (FEV1) or peak expiratory flow rate (PEFR). Airflow changes can occur:
- Spontaneously
- With treatment
- With a precipitating exposure
- With diagnostic maneuvers such as nonspecific inhalation challenge
2Patterns of association can vary and include the following:
- Symptoms of asthma that develop or worsen after a worker starts a new job.
- Symptoms after new materials are introduced on a job. A substantial period can elapse between initial exposure and development of symptoms.
- Symptoms that develop within minutes of specific activities or exposures at work.
- Delayed symptoms that occur several hours after exposure (e.g., during the evenings of workdays).
- Symptoms that occur less frequently or not at all on days away from work and on vacations.
- Symptoms that occur more frequently when the affected worker returns to work.
- Symptoms that are temporally associated with workplace exposure to an agent with irritant properties. Work-related changes in medication requirements can accompany these symptom patterns.
WRA surveillance categories
Category 1 - Work-Aggravated Asthma (WAA) / Work-Exacerbated Asthma – synonyms.
Category 2 - New-Onset Asthma (NOA)
- RADS
- Occupational Asthma (OA)
- Known asthma inducer3 with objective evidence.4
- Known asthma inducer without objective evidence.
- Unknown asthma inducer without objective evidence.
- Unknown asthma inducer without objective evidence.
Decision logic for case identification and classification
The Decision Logic Flowchart is also available.
Surveillance Case Identification
Question 1: Case of suspected WRA?
Yes: Complete a Medical, Social, and Work history; Proceed to Question #2.
Question 2: Healthcare professional's diagnosis consistent with asthma?
Yes: Proceed to Question 3.
No: Unlikely asthma, proceed to the end of the flowchart.
Question 3: An association between symptoms and work?
Yes: WRA, proceed to WRA Case Classification.
No: Unlikely work-related, proceed to the end of the flowchart.
WRA Surveillance Case Classification
Question 4: Meet the following criteria?
C1) Increased asthma symptoms or increased asthma medication use (upon entering an occupational exposure setting) experienced by a person with preexisting asthma who was symptomatic or treated with asthma medication within 2 years prior to entering that new occupational setting.
Yes: WAA, proceed to the end of the flowchart.
No: NOA, proceed to question 5.
Unknown: WRA, insufficient data to classify, proceed to the end of the flowchart.
Question 5: Meet the following criteria?
C2) New asthma symptoms that develop within 24 hours after a one-time high-level inhalation exposure (at work) to an irritant gas, fume, smoke, or vapor and that persist for at least 3 months.
Yes: RADS, proceed to the end of the flowchart.
No: OA, proceed to Occupational Asthma Case Subclassification.
OA Case Classification
Question 6: Meet the following criteria?
C3) Workplace exposure to an agent previously associated with OA using the Association of Occupational and Environmental Clinics asthmagen criteria.5
Yes: Known asthma inducer, proceed to Objective Evidence.
No: Unknown asthma inducer, proceed to Objective Evidence.
Objective Evidence
You have objective evidence, if any (at least one) of the following criteria is true.
C4) Work-related change in serially measured FEV1 or PEFR.6
C5) Work-related changes in bronchial responsiveness as measured by serial nonspecific inhalation challenge testing.7
C6) Positive response to specific inhalation challenge testing with an agent to which the patient has been exposed at work.8
End of the decision logic for work related asthma.
Surveillance case classification criteria for WRA
C1) Increased asthma symptoms or increased asthma medication use (upon entering an occupational exposure setting) experienced by a person with preexisting asthma who was symptomatic or treated with asthma medication within 2 years prior to entering that new occupational setting.
C2) New asthma symptoms that develop within 24 hours after a one-time high-level inhalation exposure (at work) to an irritant gas, fume, smoke, or vapor and that persist for at least 3 months.
C3) Workplace exposure to an agent previously associated with OA using the Association of Occupational and Environmental Clinics asthmagen criteria.5
C4) Work-related changes in serially measured FEV1 or PEFR.6
C5) Work-related changes in bronchial responsiveness as measured by serial nonspecific inhalation challenge testing.7
C6) Positive response to specific inhalation challenge testing with an agent to which the patient has been exposed at work.8
Notes
1Asthma is a chronic condition characterized by tracheobronchial tree inflammation associated with increased airways responsiveness to a variety of stimuli. Symptoms of asthma include:
- Episodic wheezing
- Chest tightness
- Cough Dyspnea
- Recurrent attacks of bronchitis with cough and sputum production
2Patterns of association can vary and include the following:
- Symptoms of asthma that develop or worsen after a worker starts a new job.
- Symptoms after new materials are introduced on a job. A substantial period can elapse between initial exposure and development of symptoms.
- Symptoms that develop within minutes of specific activities or exposures at work.
- Delayed symptoms that occur several hours after exposure (e.g., during the evenings of workdays).
- Symptoms that occur less frequently or not at all on days away from work and on vacations.
- Symptoms that occur more frequently when the affected worker returns to work.
- Symptoms that are temporally associated with workplace exposure to an agent with irritant properties. Work-related changes in medication requirements can accompany these symptom patterns.
3Inducer means agents documented in the medical literature to cause OA.
4Objective evidence means objective physiologic tests to substantiate asthma work-relatedness.
5Many agents can induce OA via a specific hypersensitivity mechanism. A comprehensive list of these asthma inducers is used for this criterion. Known asthma inducers have been designated with the letter "A" in the Association of Occupational and Environmental Clinics Code List.
6Spirometric measurements (e.g., FEV1) can be obtained before and after a person’s work shift (i.e., cross-shift spirometry). However, many cases of OA can fail to demonstrate a significant cross-shift reduction in FEV1, either because of a delayed bronchoconstrictor response or because of intermittent exposure patterns. Cross-shift spirometry testing on multiple days might help confirm the association with work. Alternatively, PEFR can be measured serially throughout the day on multiple days at and away from work using a portable peak flow meter.
7Changes in bronchial responsiveness can be measured by serial inhalation challenge testing with nonspecific agents (e.g., using methacholine or histamine). Evidence of work-relatedness is manifested by increased bronchial responsiveness (i.e., bronchoconstriction at lower inhaled doses of methacholine or histamine) following work exposures and decreased or normal bronchial responsiveness after a period away from work.
8Specific inhalation challenge testing has distinct objectives, including the following:
- Identifying previously unrecognized causes of OA.
- Confirming a diagnosis of OA.
- Identifying the causative agent when more than one allergen is present in the occupational environment and identification of the causative agent is essential for management.
Specific inhalation challenge testing is potentially dangerous and should be performed by experienced personnel in a hospital setting where resuscitation facilities are available and frequent observations can be made over sufficient time to monitor for delayed reactions. Specific inhalation challenge testing is usually not necessary for clinical diagnosis of OA.