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Occupational asthma

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Occupational asthma …

Occupational asthma

Presented by Theerapan Songnuy, MD.

On May 10, 2013

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  • 1. Theerapan Songnuy M.D.
  • 2. Overview Definition Etiology Diagnosis Conclusion
  • 3. Occupational Asthma ( OA)Jean Luc Malo & Moira Chan-Yeung. Occupational Asthma. In Middleton 7th edition. 939-953.-A type of asthma caused by the workplace-Classified into 2 types:1. OA with a latency period need to getsensitized to an agent in the workplace2. OA without a latency period, occur afteraccidentally inhale at work-Of the first type, mostly caused by high ( protein)molecular-weight agents-High-molecular weight agent induced by IgE-mediated mechanism- LMW agents act as hapten
  • 4. Jean Luc Malo & Moira Chan-Yeung. Occupational Asthma. In Middleton 7th edition.939-953.
  • 5. lJean Luc Malo & Moira Chan-Yeung. Occupational Asthma. In Middleton 7th edition. 939-953.
  • 6. JACI 2013; 131: 704-10
  • 7. Aims1. Compare the clinical , functional and inflammatorycharacteristics of workers with work-exacerbatedasthma and occupational asthma2. Compare health care use and related costs betweenwork-exacerbated asthma and occupational asthma,work-related asthma and non-work-related asthmaJACI 2013; 131: 704-10
  • 8. Materials & Methods A prospective cohort study with a 2-year follow-up Subjects:- Asthmatic patients referred for suspectedwork-related asthma- Two tertiary centers in Quebec, Canada- From 2003-2008JACI 2013; 131: 704-10
  • 9. Materials & Methods Subjects :- At first visit ; questionnaires, SPT, PFT,methacholine inhalation challenge test,sputum induction- Be classified as ; inflammatory phenotypes- Eosiophilic ( sputum EO > 3%)- Nutrophilic ( sputum N > 61%)- Paucigranulocytic ( sputum EO< 3%,N < 61%)- Mixed ( sputum EO> 3% , N > 61%)
  • 10. Materials & Methods Severe asthma: an ER visit or a hospitalization Specific inhalation challenges to occupational agentswere done when asthma possibly related to work Asthma diagnosis:- FEV1<80% of predicted value- FEV1/FVC < 0.7- improvement in FEV1 > 12% after bronchodilator- If absence of reversible airflow limitation,PC20 value should < 16 mg/mlJACI 2013; 131: 704-10
  • 11. Materials & Methods Diagnosis of occupational asthma:- Positive specific inhalation challenge test- Worsening asthma symptoms while at workDiagnosis of work-exacerbation asthma:- Negative specific inhalation challenge test- Worsening asthma symptoms while at work
  • 12. Materials & Methods Health care use and related costs- From administrative database- Focusing on physician’s cost, ER visit &hospitalization
  • 13. JACI 2013; 131: 704-10
  • 14. JACI 2013; 131: 704-10
  • 15. JACI 2013; 131: 704-10
  • 16. JACI 2013; 131: 704-10
  • 17. JACI 2013; 131: 704-10
  • 18. JACI 2013; 131: 704-10
  • 19. Conclusion Workers with WEA have more severe clinicalthan workers with occupational asthma WEA is associated with a non-eosinophilicphenotype Both WEA & occupational asthma havegreater health care use & 10-fold higher directcosts than NWRA
  • 20. Diagnostic tools forOccupational Asthma Specific inhalation challenge ( standard test) Combination of Peak Expiratory Flow Rate &sputum eosinophil count Exhaled Breath Condensate pH test
  • 21. l
  • 22. Aims To characterize the threshold duration ofexposure needed to elicit an asthmaticreaction during specific inhalation challengewith various occupational agents To determine the duration of exposure thatshould be complete before the test can beconsidered negative
  • 23. Materials & Methods A retrospective study Centre Hospitalier Universitaire de Mont-Godinne, Universite Catholique de Louvain,Yvain,Belgium From Jan 1992-Dec 2011 Data records were reviewed All subjects investigated for possible occupationalasthma with positive test for specific inhalationchallenge
  • 24. Materials & Methods Specific Inhalation Challenge:- Occupational agents were generated in five-cubic-meter cubicles using a realistic approach- Asthma medications were stopped according to theirduration of action- Inhaled steroid was halted 72 hr prior to the test- The level of exposure during SICs was monitoredonly for isocyanates using an MDA 7100 monitor( MDA Scienctific Inc, Glenview, IL) & was kept belowthe ceiling value of 20 ppb.
  • 25. Materials & Methods Spirometry was obtained at:- baseline, q 15 min * 4 timesq 30 min * 2 timesq 1 hr for a total of 6 hr after the end of exposure- The baseline level of BHR to histamine & sputum eosinophilcount were assessed at the end of control day- Re-assessed 6 & 24 hr after the active challenge- Degree of non-specific BHR was assessed as provocativeconcentration of histamine causing a 20% fall in FEV1 ( PC20)- Positive SIC : sustained > 20% fall in FEV1 was recorded on 2consecutive assessments
  • 26. Materials & Methods On the first day :- Using “ control” agent for 30 min to ensureFEV1 fluctuation < 12% of baseline- “ control” agent according to the nature ofoccupational agent suspected causing asthma( ie ; use lactose powder for flour)
  • 27. Materials & Methods The second day:- Use a suspected agent- A duration of exposure gradually increasedfrom 1 , 4, 10, 15, 30, 60 min until a > 20%fall in FEV1 occurred or 2 hr was reached- Who did not show a >20% fall in FEV1, had torepeat for 3 hr on the next day- Negative test : challenging at least 240 minwithout significant change- If > 3-fold decrease in post-challenge PC20 orincrease in sputum > 3% compared to controlvalue, further challenge will be repeated
  • 28. Conclusion Sensitivity of Specific InhalationChallenge for diagnosis occupationalasthma depend on duration of challengeexposure Need markers such as post-challengelevel of non-specific bronchialresponsiveness to histamine , sputumeosinophil count
  • 29. Aim To evaluate the utility of exhaled breathcondensate ( EBC) pH for the diagnosisof occupational asthma
  • 30. Materials & Methods A prospective study Total of 37 patients suspectedoccupational asthma Exclusion criteria:- Seasonal asthma- Can not join PEF, SIC, EBC pH* Allow to take asthma medication butdon’t change type or dose
  • 31. Materials & Methods Spirometry & Methacholine Test- A Datospir 200 system ( Sibel, Barcelona, Spain) used for spirometry- A Mefar MB3 dosimeter ( Ele H2O, Medically, Brescia, Italy) forMethacholine test- Increasing dose of methacholine ( 0.03-16 mg/ml) were inhaled at 3-min intervals until FEV1 fell by 20% of baseline or max dose wasinhaled ( PC 20)- Negative test defined as PC20 > 16 mg/ml- Dose response rate : last FEV1 decline ( %) / last dose administered
  • 32. Materials & Methods Monitoring Peak Expiratory Flow Rates- Serial PEF during 2 wk at work & 2 wk off work- A Mini-Wright portable peak flow meter ( ClementClarke International, UK) & diary cards- Record 4 times a day- PEF graphs were interpreted by 3 experiencedindependent readers- Positive test : evidence changes between exposureperiod- PEF recording was computerized by Oasys-2 software- Suggestive Occupational asthma : score > 2.51
  • 33. Materials & Methods Exhaled Breath Condensate Collection & pH Measurement- Collecting during tidal breating with a commerciallycondensor ( EcoScreen; Jaeger,Wurzburg, Germany)- To determine ventilatory pattern, spirometer( EcoVent; Jaeger ) was connected- Patients were prohibited from foods 2 hr before samplecollection- A fixed volume of 150 liters of exhaled breath was collectedper patient- Sample was divided into 500 ul aliquots in 2-4 plastic tubes
  • 34. Materials & Methods pH was measured in 1 aliquot after collectionimmediately Another one was measured after de-aerationwith helium ( 350ml/min for 10 min) Using a model GLP 21 calibrated Ph meter( Crison Instruments SA, Barcelona, Spain)with an accuracy of +- 0.01 pH A probe ( Crison 5028) was calibrated dailywith standard Ph 7.02 & 4.00 buffers
  • 35. Materials & Methods Specific Inhalation Challenge:- Standard test for diagnosis- Using substances suspected the cause of the patient’sasthma*- A placebo was done before an actual test- Measuring FEV1, FVC q 10 min during first hr followingexposure & q 1 hr until 15 hr post-inhalation- Positive test : FEV1 decrease > 20% baseline
  • 36. j
  • 37. Conclusion SIC is a gold standard to diagnosisoccupational asthma EBC pH is an easily performed,inexpensive, & noninvasive method If SIC can’t be done, PEF & inducedsputum eosinophil count are chosen EBC pH alone or combine with PEF maybe a good option
  • 38. Thank You Very Much

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