Diagnosing occupational asthma

Abstract

Summary Making an accurate diagnosis of occupational asthma (OA) is, generally, important. The condition has not only significant health consequences for affected workers, but also substantial socio‐economic impacts for workers, their employers and wider society. Missing a diagnosis of OA may lead to continued exposure to a causative agent and progressive worsening of disease; conversely, diagnosing OA when it is not present may lead to inappropriate removal from exposure and unnecessary financial and social consequences. While the most accurate investigation is specific inhalation challenge in an experienced centre, this is a scarce resource, and in many cases, reliance is on other tests. This review provides a technical dossier of the diagnostic value of the available methods which include an appropriate clinical history, the use of specific immunology and measurement of inflammatory markers, and various methods of relating functional changes in airway calibre to periods at work. It is recommended that these approaches are used iteratively and in judicious combination, in cognizance of the individual patient's circumstances and requirements. Based on available evidence, a working diagnostic algorithm is proposed that can be adapted to the suspected agent, purpose of diagnosis and available resources. For better or worse, many of the techniques – and their interpretation – are available only in specialized centres and where there is room for doubt, referral to such a centre is probably wise. Accordingly, the implementation or development of such specialized centres with appropriate equipment and expertise should greatly improve the diagnostic evaluation of work‐related asthma.

Occupational contact urticaria and protein contact dermatitis: causes and concomitant airway diseases

“…Placebo-controlled challenges were performed in a challenge chamber or with commercial allergen extracts by use of a dosimeter, in accordance with the methods described by Vanhanen et al (12). In addition, to confirm an occupational asthma diagnosis, we used peak expiratory flow monitoring at work and off work, combined with positive prick test or specific IgE results (13). Local nasal provocation tests, in accordance with the methods described by Airaksinen et al (14), were used when the patients had only upper respiratory symptoms, and the causative agent was not considered to be particularly irritating to the mucous membrane.…”

Novel clinical scores for occupational asthma due to exposure to high-molecular-weight agents

“…This is in agreement with a systematic review by Beach and colleagues,23 which concluded that the diagnosis of OA in the absence of SIC should preferably be determined by a combination of NSBHR and specific sensitisation tests. Vandenplas and colleagues7 proposed NSBHR and specific SPT tests as the first step of the stepwise approach for diagnosing OA, and the American Colleague of Occupational and Environmental Medicine24 also strongly recommended these two tests in diagnosing OA.…”

“…In places without access to SIC evaluations, an estimation of the probability of occupational asthma for individuals based on their unique characteristics by this model can guide physicians at the secondary care level (specialists: ie, respirologists, occupational medicine physicians) in deciding whether: (A) they could remove workers from the exposing agents in the workplace and initiate treatment or (B) they should consider further evaluation of the clinical characteristics and order other test to confirm the diagnosis (eg, serial measurement of peak expiratory flow and/or NSBHR and/or induced sputum at work and off work) 7. Furthermore, this model could be used to assess workers with workers’ compensation claims.…”

“…It has a good discriminative ability (AUC 0.75), but as in the case of questionnaires in general, it is subject to a low specificity7 as shown in figure 1. The use of the final model with objective tests would be restricted to physicians with access to both SPT to specific allergen such as flour and methacholine challenge tests.…”

“…Worldwide, especially in developing countries, OA remains under-recognised and poorly diagnosed 2. SIC as the reference test7 is only available in a few specialised centres worldwide. In Canada, SIC is recommended to confirm the diagnosis of OA in Quebec, but not in other provinces 10…”