The management
of work-related asthma
OEMAC 2010
Jeremy Beach
University of Alberta
Potential conflicts of interest
• Have received research funding from
Alberta WCB and AHRQ.
• Was a member of ACCP WRA guidelines
committee
• No shareholdings, payments or honoraria
from pharmaceutical companies or
equipment manufacturing companies.
Learning objectives
• Participants will understand the diagnosis and management
of work related asthma based on the most recent guidelines
• Participants will understand current issues surrounding
surveillance of work related asthma including occupational
asthma
• Participants will understand elements of
management including removal from exposure
and the role of evidence based practice in the
management of work related asthma
Sources of information
•
•
•
•
AHRQ systematic review
ACCP guidelines
BOHRF guidelines
Cochrane review – specifically on workplace
interventions
• Other papers/guidelines/articles
References at end
Definition of work-related asthma
• Occupational asthma- asthma caused or
contributed to by an exposure at work:
– With latency - sensitisers
– Without latency – irritants, RADS
• Work aggravated asthma
– Pre-existing asthma made worse by simple
physical exposure at work
The Individual with work-related asthma
Questions about management
• Is complete removal from exposure necessary?
– Is reduction of exposure adequate
– Can PPE safely be used
• Are there any specific medications of particular
use in OA
– Steroids after an acute exposure
• What is the economic/social impact of OA for
individual affected, and society
AHRQ - Methods
• Search terms identified
• Indexing databases searched:
– MEDLINE, EMBASE, Dissertation abstracts, Expanded academic,
National Agricultural and Safety Database, CINHAL, Biological
abstracts, Agricola, Trials registries, Web of Science, hand search,
grey literature
• Reviewed for relevance and quality
• Relevant data extracted
– Estimate sensitivity and specificity for diagnosis
– Assess outcome for management
Initial independent references from all
databases
(n=11366)
Citations with potential
relevance (n=632)
First screening of titles and abstracts using
general criteria
13 studies were assessed for
diagnosis and management
16 studies were unobtainable
Diagnosis Review
Management Review
Full text articles with potential relevance
(n=493)
Reference lists, authors’ lists,
conference presentations
* 33 studies waiting
assessment
Met inclusion criteria (n=109)
Second screening
with specific criteria
Full text articles with potential relevance
(n=152)
Reference lists, authors’ lists,
conference presentations
Met inclusion criteria (n=58)
Management
• Needed to classify ongoing exposure status,
while on optimal treatment
– Continued unchanged
– Reduced
– Ceased
Management
• Most data available for FEV1, NSBPT, and
use of medication for outcomes
– see figures following
– No metanalysis - heterogeneity
• Symptoms
– Removal – majority had some improvement
• Few had complete resolution
– Exposed – continued unchanged or deteriorated
20
Removed
10
Exposure
v FEV1
0
Change in Average %predicted FEV-1
-10
-20
0
2
20
4
6
8
6
8
Exposed
10
0
-10
-20
0
2
20
4
Reduced
10
0
W - HMW
-10
B - LMW
-20
0
2
4
6
8
Length of Follow-up (years)
Size of plotting character is proportional to number of patients follow ed
G - mixed
4
Ratio of Follow-up and Baseline Mean Hyperesponsiveness
Exposure
v NSBPT
Removed
5
3
2
1
0
0
2
4
6
8
6
8
Exposed
5
4
3
2
1
0
0
2
4
Reduced
5
4
3
W - HMW
2
1
B - LMW
0
0
2
4
6
8
Length of Follow-up (years)
Size of plotting character is proportional to number of patients follow ed
G - mixed
Removed
100
Exposure v
medication
use
80
60
40
20
Percent of Patients on Medications
0
0
2
4
6
8
10
12
14
10
12
14
Exposed
100
80
60
40
20
0
0
2
4
6
8
Reduced
100
80
60
W - HMW
40
20
B - LMW
0
0
2
4
6
8
10
12
14
Length of Follow-up (years)
Size of plotting character is proportional to number of patients follow ed
G - mixed
Cochrane Review: WORKPLACE INTERVENTIONS
FOR TREATMENT OF OCCUPATIONAL ASTHMA
• INTERVENTIONS :
• 12 Stop Exp v Continue
Exp
• 3 Less Exp v Cont Exp
• 2 Stop Exp v Less Exp
• 1 Education
• Total: 15 English
articles
•
-
AGENTS :
4 Western Red Cedar
3 TDI
2 NRL
2 Various
1 Cobalt
1 Colophony
1 Potroom
1 Mixed farming
Cochrane review – pre pelininary
Risk Ratio, M-H, Random, 95%CI
Systematic review - Rachiotis
• Patients with shortest duration of exposure
had highest rate of recovery
But
• Effect not linear
• No clear patterns in between-study
comparisons
Results - Trials
• Two studies suggest inhaled steroids (5-6
months) help recovery once exposure ceases.
• Little other good evidence. Effectiveness of
medication probably similar to non WRA.
Results - Trials
– Wheat flour immunotherapy:
• Decreased serum specific IgE;
• Less skin prick sensitivity;
• Less non-specific bronchial reactivity.
– Fel d1 effective in non-OA
– Respiratory PPE significantly improved specific
airway resistance.
– Use of low protein hypoallergenic gloves
reduced asthma exacerbations.
Citation
Removed/Unemployed
Exposed or Reduced
-84 percent (69/82^)
-$4,203.72 USD/year
-$5,863.88 USD/year
-54 percent (56/78^)
39/112 unemployed
-$368.14 USD/month
-$609.96 USD/month*
53/128 unemployed
-19 percent (20/104^)
-$268.71 USD/year
-$3820.27 USD/year
-35 percent (14/34^)
-$12.46 USD
+$13.17 USD
Income
Ameille et al.
Moscato et al.
Gannon et al.
Marabini et al.
Pharmaceutical
Costs/month
Moscato et al.
-$256.38 USD/month
Note: * = unemployed; + = reduced exposure; ^ = perception of reduced income
Financial consequences
• OA results in loss of income
• Greatest loss was in those removed from
workplace, but even those who stayed with
same employer lost income.
• Drug costs higher in those with ongoing
exposure
• Unemployment a relatively common
outcome
Compensation
• In Canada WCB system
– Recognition and reporting a prerequisite
– Often straightforward with clear case of
sensitiser induced OA
– Can be much more difficult when information
on exposures is difficult to obtain, or when
disease difficult to characterise – irritant OA v
WEA v COPD
Management of work-related asthma
at a business/societal level
• Questions
– Is primary prevention effective?
– Is health surveillance useful in a workplace
with asthmagen exposure
– How can long term consequences/costs be
minimised.
Primary prevention
• Risk assessment
• Hierarchy of control
– Some evidence of success
• Substitution – latex gloves
• Encapsulation of detergent enzymes – control
• Autobody painters, acid anhydride manufacture –
PPE
• Recognising case as sentinel event
Heath surveillance
• Pre-employment
– Atopy/smoking are risk factors.
• Common characteristics - discrimination
• No evidence excluding significantly reduces risk
• Periodic
– Sensitisation
• Probability of progression high once sensitised
– Disease
• Difficulty of finding sensitive and specific test
• Importance of education/awareness
• Estimated cost per case of disability prevented = US $64,000
Minimising costs and consequences
• Estimated mean compensation cost of a case of
OA in Quebec 1998-2002 >$90,000
• Factors associated with increased cost
•
•
•
•
Male
Age >40
LMW agent
Severity of disease
(FEV1 <80%/use of inhaled steroids/PC20 <16 mg/ml)
• Changing employer
• >1 year with symptoms prior to diagnosis
Factors associated with increased
time to diagnosis
• Age > 40
• Salary >$30,000 - possibly
• OA due to HMW
? Worth focussing surveillance
Conclusions - management
• Those with OA who remain exposed tend to
experience decreased FEV1, increased NSBR, and
will usually require medication.
• Those with OA who cease exposure tend to
experience improved FEV1 and decreased NSBR.
The majority still require ongoing medication use.
• The majority of those who cease exposure report
ongoing symptoms, and some experience
decreasing FEV1 despite exposure ceasing
Thank you
Questions
References/reading
1.
2.
3.
4.
5.
6.
7.
8.
Beach J, Rowe BH, Blitz S, Crumley E, Hooton N, Russell K, Spooner C, Klassen T. Evidence
Report/Technology assessment No. 129. Diagnosis and management of work-related asthma.
AHRQ Publication No. 06-E003-2. Rockville MD: Agency for Healthcare Research and Quality,
2005.
Tarlo SM, Balmes J, Balkissoon R, Beach J, Beckett W, Bernstein D, Blanc PD, Brooks SM,
Cowl CT, Daroowalla F, Harber P, Lemiere C, Liss GM, Pacheco KA, Redlich CA, Rowe B,
Heitzer J. ACCP Consensus Statement: Diagnosis and Management of Work-related Asthma.
Chest 2008; 134 (3 Suppl): 1s-41s
Newman Taylor AJ, Nicholson PJ, Cullinan P, Boyle C, Burge PS. Guidelines for the prevention,
identification& management of occupational asthma: evidence review and recommendations.
BOHRF, London, 2004.
Rachiotis G, Savani R, Brant A, MacNeill SJ, Newman Taylor A, Cullinan P. Outcome of
occupational asthma after cessation of exposure: a systematic review. Thorax. 2007; 62: 147-52.
Malo JL, L’Archeveque J, Ghezzo H. Direct costs of occupational asthma in Quebec between
1988 and 2002. Can Respir J 2008; 15: 413-416.
Miedinger D, Malo JL, Ghezzo H, L’Archeveque J, Zunzunegui M-V. Factors influencing
duration of exposure with symptoms and costs of occupational asthma. Eur Repir J 2010,
published on line
de Groene G, Pal TM, Verbeek JH, Beach J, Tarlo SM, Frings-Dresen MHW. Workplace
interventions for treatment of occupational asthma. Cochrane Database of Systematic Reviews
2007 , Issue 1 . Art. No.: CD006308. DOI: 10.1002/14651858.CD006308
Wild DM, Redlich CA, Paltiel AD. Surveillance for isocyanate asthma: a model based cost
effectiveness analysis Occup Environ Med 2005; 62: 743-749.
Cochrane review
Pre-Pre-liminary results:
Improvement of Asthma Symptoms