Allergens causing occupational asthma: an evidence-based evaluation of the literature

The aim of this work is to provide an evidence-based evaluation and overview of causative substances in order to improve disease management.

We conducted a database search with MEDLINE via PubMed, screened reference lists of relevant reviews and matched our findings with a list of agents denoted as "may cause sensitisation by inhalation" by the phrase H334 (till 2011 R42). After exclusion of inappropriate publications, quality of the selected studies was rated with the Scottish Intercollegiate Guideline Network (SIGN) grading system. The evidence level for each causative agent was graded using the modified Royal College of General Practitioners (RCGP) three-star system.

A total of 865 relevant papers were identified, which covered 372 different causes of allergic work-related asthma. The highest level achieved using the SIGN grading system was 2++ indicating a high-quality study with a very low risk of confounding or bias and a high probability of a causal relationship. According to the modified RCGP three-star grading system, the strongest evidence of association with an individual agent, profession or worksite ("***") was found to be the co-exposure to various laboratory animals. An association with moderate evidence level ("**") was obtained for α-amylase from Aspergillus oryzae, various enzymes from Bacillus subtilis, papain, bakery (flour, amylase, storage mites), western red cedar, latex, psyllium, farming (animals, cereal, hay, straw and storage mites), storage mites, rat, carmine, egg proteins, atlantic salmon, fishmeal, norway lobster, prawn, snow crab, seafood, trout and turbot, reactive dyes, toluene diisocyanates and platinum salts.

This work comprises the largest list of occupational agents and worksites causing allergic asthma. For the first time, these agents are assessed in an evidence-based manner. The identified respiratory allergic agents or worksites with at least moderate evidence for causing work-related asthma may help primary care physicians and occupational physicians in diagnostics and management of cases suffering from work-related asthma. Furthermore, this work may possibly provide a major contribution to prevention and may also initiate more detailed investigations for broadening and updating these evidence-based evaluations.