Reference

Malo JL, Ghezzo H, L'Archeveque J et al, Is The Clinical History A Satisfactory Means Of Diagnosing Occupational Asthma?, Am Rev Respir Dis, 1991;143:528-532,

BOHRF Original Authors' Main Conclusions

The original authors' main conclusions are taken from Abstract, Results and Discussion. They are decided upon by the authors of the BOHRF occupational asthma guidelines and form part of the guidelines.

Study assessed accuracy of a diagnosis of occupational asthma made upon basis of an open medical questionnaire. 162 subjects were referred to clinic and assessed because their physicians thought their asthma might be work-related. They filled in a questionnaire and then underwent objective assessment with specific inhalation challenges (72), monitoring of peak expiratory flow rates for periods at work and away from work (29), or both (61). 75 subjects (46%) were shown to have occupational asthma. Symptoms alone (type and timing) did not provide a satisfactory differentiation between those subjects with and without occupational asthma. Positive predictive value of questionnaire diagnosis of occupational asthma found to be low (63%) but negative predictive value higher (83%). Therefore, if questionnaire suggests diagnosis of occupational asthma, then >50% chance that the diagnosis is correct. The clinical history taken by physicians with experience in occupational asthma is not a satisfactory diagnostic tool and the presence or worsening of symptoms at work and improvement during weekends and holidays was not conclusively linked with occupational asthma. Normal bronchial hyper-reactivity was observed in 12/75 with proven occupational asthma. Study suggests that an open medical questionnaire is not a satisfactory means of diagnosing occupational asthma.

BOHRF Associated Evidence Statements

The BOHRF occupational asthma guidelines state that this reference is associated with the following evidence statements

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2+

In the clinical setting questionnaires that identify symptoms of wheeze and/or shortness of breath which improve on days away from work or on holiday have a high sensitivity, but relatively low specificity for occupational asthma.

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3

Free histories taken by experts have high sensitivity, but their specificity may be lower.

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2++

A large number of concordant studies from different centres using different methodologies demonstrated that increased non-specific reactivity is often found in workers with occupational asthma. There are however many reports of normal methacholine or histamine reactivity within 24 hours of exposure in workers with confirmed occupational asthma.