Concise guidance: diagnosis, management and prevention of occupational asthma

Abstract

-This concise guidance, prepared for physicians, summarises the British Occupational Health Research Foundation guideline for the prevention, identification and management of occupational asthma. Approximately one in six people of working age who develop asthma have work-related asthma, where work has either caused or aggravated their disease. Physicians who assess working adults with asthma need to ask the patient about their job and the materials they work with, and be aware of those that carry particular risks; they should also ask whether symptoms improve regularly on days away from work. A diagnosis of occupational asthma (ie asthma caused by work) should not be made on the basis of history alone, but be supported by immunological and physiological investigations of proven diagnostic benefit. Following a validated diagnosis of occupational asthma, physicians should recommend early avoidance of further exposure, because this offers the best chance of complete recovery. If appropriate and timely interventions are not taken, the prognosis of occupational asthma is poor, with only approximately one-third of workers achieving full symptomatic recovery.

Guidelines for the management of work-related asthma

“…2) Many workers with work-related asthma have increased nonspecific bronchial hyperresponsiveness (NSBHR) to methacholine or histamine, for example. However, a normal measurement cannot be used to exclude work-related asthma as there are many reports of normal bronchial responsiveness within 24 h of exposure in workers with confirmed occupational asthma (***) [26,46,47].…”

“…8) Carefully controlled specific inhalative challenge (SIC) tests come closest to a gold standard test for many agents causing occupational asthma (*) [46]. 9) A negative specific inhalative challenge test in a worker with otherwise good evidence of occupational asthma is not sufficient to exclude the diagnosis (**) [49,50,55,[62][63][64][65][66][67].…”

“…The statements above are based, in the main, on the BOHRF guidelines [46], and are compatible with the AHRQ review [26] and the ACCP guidelines [3]. The evidence for serial measurements of peak expiratory flow (PEF) is taken from an evidence-based review [48] and is compatible with the AHRQ meta-analysis.…”

Is spirometry essential in diagnosing asthma? No

“…9,10 Airflow obstruction in asthma is worse during the night and early morning, so lung function indices obtained during office hours may not accurately reflect variability. When spirometry is normal in people with suspected asthma, a pragmatic alternative is to provide a peak flow meter and instructions to record the best of three readings twice a day, when symptoms occur, and if appropriate, in combination with a trial of treatment.…”

Differences in serial lung function recorded on four data-logging meters

“…They are particularly useful in the evaluation of patients with suspected work-related asthma and are recommended as the first step in physiological confirmation by evidence-based guidelines [1][2][3]. Workers are required to document their PEF readings over a period of time, usually for 4 weeks performing them every 2 h. These are then plotted to ascertain whether they are consistent with the diagnosis of occupational asthma.…”