1 Occupational asthma Provocation tests and lung function measurements in diagnostics Treatment and follow up Ritva Piipari, TTL

2 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

3 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

5 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.

6 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

7 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

8 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

9 Performing challenge tests 1. 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

10 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

11 Criteria for a positive provocation test reaction minimum 20% FEV 1 /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)

12 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

14 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)

15 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

16 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

17 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

18 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

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