1

Occupational asthma

•Provocation tests and lung function

measurements in diagnostics

•Treatment and follow up

Ritva Piipari, TTL

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Confirming the diagnosis of occupational asthma

• Specific challenge tests= international golden standard for diagnosis

of occupational asthma

• to prove the cause-effect relationship between the agent from the workplace and the asthmatic reaction in individual level

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Occupational asthma, diagnostics

• Work related asthmatic symptoms

• Exposure to a sensitizing agent at work

• Cause-effect relationship between the exposure material and asthma– Sensitization (skin prick tests/specific IgE antibodies)– Positive provocation test– Typical long-term PEF surveillance

4

Diagnostics of occupational asthma

• PEF-surveillance at home and at the workplace always, if possible

– Positive finding supports the diagnosis

– Negative finding does not exclude the diagnosis

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Prerequirements for challenge tests

1. Clinical picture fits with occupational asthma, but the diagnosis has not yet been verified

2. Asthma is stable. Inhaled steroid may be used, stable dose every evening.

3. Differential diagnostics done.

4. No contraindications to challenge tests.

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Contraindications to challenge tests

• Acute infections

• Unstable asthma or some other disease

• Poor lung function

• Facts, that prevent proper interpretation of the challenge tests (e.g. non co-operating patient)

• Highly toxic or irritative substances

• Anaphylactic or otherwise very strong reaction to the challenge material in history

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Requirements, when performing challenge tests

• 24-hour follow up and facilities to treat acute and late asthmatic ( and other) reactions

• Aduquate challenge chamber and well trained staff

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Challenge chamber

• Adequate ventilation

• Safety of the patient

• Safety of the personnel– exhaust ventilation– easy to clean

• Facilities for generation of dusts, vapors and aerosols in controlled concentrations

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Performing challenge tests1. Confirm, that the asthma is stable

– symptoms, FEV1/PEF 24-hour follow-up, spirometry (histamine/metacholine challenge)

2. Challenge with control material– To confirm, that asthma does not react to nonspecific agents– Challenge material and method individually chosen, in order to

mimic the challenge method and material of the active agent challenge

– Control challenge must be negative– Challenge with active agent is compared with the control challenge

3. Challenge with active agent

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Challenge test with active agent

• Commercial allergen extracts

• Tests simulating work tasks (patient handles the material from workplace)– Individual planning: challenge materia,

concentration, duration of test e.g.– Occupational hygienist/chemist consultations

when needed– Controlled concentrations

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Criteria for a positive provocation test reaction

• minimum 20% FEV1/PEF decrease compared to baseline before exposure and to control test

• tests with allergen extracts– minimum 15% decrease in immediate reaction

(during one hour after challenge)

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Criteria for a positive provocation test reaction

• Findings supporting positive challenge test:– symptoms– wheezing rales– dose-response– increase in hyperreactivity– recovery of the reaction on the following day– increase in exhaled nitric oxide?– increase in peripheral resistance (impulse

oscillometry)

13(Keuhkosairaudet, Duodecim 2000)

Isosyanaatti(MDI)altistustesti, välitön astmareaktio

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Diagnostics of occupational asthma

• Provocation tests not necessary

– typical work related asthmatic symptoms– exposure to a known sensitizer– sensitization confirmed– asthma and work related bronchoconstriction

confirmed (asthma diagnosis done, PEF-surveillance at home and at the workplace typical for occupational asthma)

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Procedures after diagnosing occupational asthma

• Statements needed (medical certificates, Announcement of a new occupational disease to the Register of Occupational Diseases as well to local officials in Finland e.g.)

• Stopping/minimizing exposure at the workplace

• Treatment and follow up of asthma

Aim: To discontinue exposure in order to prevent the disease from worsening/getting chronic or make it possible for the disease to heal totally

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Procedures after diagnosing occupational asthma

How to discontinue/minimize exposure?

• Changing agents used in the workplace

• Changing work tasks/working area/environment (replacement in another kind of work task or working environment)

• Changing the work tasks

• Restrictions to the worker

• Use of respiratory protective device• Re-education to another occupation ( in Finland legally set that

the insurance company of the employer is responsible for re-education)

• Retirement

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Treatment and follow up of occupational asthma

• Usually regular asthma medication needed

• In the follow up the need of asthma medication depends on the disease severity, which varies substantially individually

• After discontinuing exposure– Some patients recover totally

– In some patients mild asthma symptoms continue to exist

– In some patients asthma gets worse

• Follow up by both occupational health care and pulmonogist needed

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Prevention of occupational asthma

• Is dependent on co-operation between workplace and occupational health care– Actual knowledge of the sensitizing agents used in the

workplace– Work hygienic tasks to minimize exposure and exposure

assessments, when needed– Guidance of the right kind of working methods– In occasional exposures possibility to use respiratory

protective device– Occupational health care services: check out of workers, when

symptoms exist and follow up of lung function measurements

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1994 1995 1996 1997 1998 1999 2000 2001 2002

Patients Challenge tests OA cases diagnosed

Patients examined at the patient ward of FIOH, challenge tests done and occupational asthma (OA) cases diagnosed in 1994-2002