Pre Placement Assessment Assessing Risk

The prevention of allergy should begin before exposure to allergen occurs. Assessment of potential animal workers prior to commencing work with animals is good practice, and also a legal duty in some jurisdictions. Partly, the purpose of this assessment is to consider individual vulnerability to allergy. It is also to consider the worker's capability to do the proposed work and determine the need for interventions and adjustments (such as immunization against infectious diseases and provision of lifting aids). If individuals who will definitely develop allergy could be identified reliably prior to exposure then they could be excluded from the workplace. The identification of these vulnerable people is highly desirable, but it it feasible?

Atopy is a genetic predisposition to develop specific IgE and allergic reactions (e.g., skin rashes, rhinoconjunctivitis, asthma).9 The majority of studies have indicated that workers who have a personal history of atopy are more likely to develop LAA, although this has not been a universal finding.10 Some investigators have identified an association between family history of atopy and the development of LAA, but others have found no association.10 It is likely that any association between family history and the development of LAA is weak.

Some studies have examined the association between biological indicators of atopy (skin testing and immunoassay) and allergy. Most of these studies have been a cross-sectional design and have examined the association of atopy in established cases of LAA. This limits their usefulness in establishing the predictive value of these indicators in workers without LAA. There is a clear association between skintest reactivity to animal allergens and allergic symptoms. Pooled data from seven studies has shown 51 to 69% of people allergic to rats or mice have positive skin tests to allergens from these animals.4

An association between total IgE and the later development of allergy has been reported.14 Only one study has examined the predictive value of radioallergosorbent tests (RAST) for IgE specific to the animal allergen. A combination of a positive RAST and positive skin test was 87.4% predictive of the development of LAA.12

Even using the best predictive tests (personal history and biological indicators of atopy) to exclude vulnerable workers, more people who would never develop symptoms would be excluded than people who would become allergic.12,13 While it is possible to identify asymptomatic workers at the start of employment who are at increased risk of developing LAA, it is not practical nor ethical to implement effective screening criteria and exclude them from work. If the implementation of a comprehensive allergen-control program has reduced the incidence of allergy to low levels, the value of these tests as predictors of LAA is similarly reduced.

Pre-placement assessment is still worthwhile. It is the first opportunity to assess the vulnerability of the candidate and counsel him or her on the measures he or she should take to minimize the risk of developing allergy. It is an opportunity to establish baseline data and carry out baseline investigations against which future assessments can be compared. Serum banking is, however, not recommended.6 Some candidates will have a history of exposure to laboratory animals (either from their studies, work, or from pets) and may report preexisting allergies. Many of these will be able to begin their intended occupation (with appropriate adjustments and restrictions), but some will not. If a candidate reports anaphylactic reactions or occupational asthma, then the risk of continued exposure to the relevant allergen is likely to be unacceptable.

Counseling at health assessment should be an integral part of any allergy-prevention program. In addition to helping people exposed to allergens understand the potential health effects and the need for early reporting, it is an opportunity to explain the steps they can take to protect their own health and to reinforce the importance of engineering, procedural, and behavioral controls. It provides an opportunity to explain individual risk in the context of the proposed work (and exposure pattern), the local experience of allergy incidence, and the individual's tendency to develop allergy. This information allows the candidates to make their own informed decision about the risks of the proposed employment.

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