Reference

Cote J, Kennedy S, ChanYeung M, Sensitivity And Specificity Of PC20 And Peak Expiratory Flow Rate In Cedar Asthma, J Allergy Clin Immunol, 1990;85:592-598,

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.

The diagnosis of red cedar asthma is usually confirmed by a specific challenge with plicatic acid. Study aimed to determine the sensitivity and specificity of two other diagnostic tests, prolonged recording expiratory flow rate (PEFR) and measurement of bronchial responsiveness (provocative dose of methacholine causing a 20% fall in FEV1 [PC20 methacholine]). 23 patients with suspected cedar asthma recorded PEFR during 2 weeks away from work and 3 weeks at work. Plicatic acid challenge test was performed at the end of the study; 14 patients reacted, whereas 9 patients did not. Using the plicatic acid challenge test as the gold standard, the sensitivity and specificity of PEFR recordings were 86% and 89%; changes in PC20, 62% and 78%; and 93% and 45% for a positive clinical history. The combination of PEFR and clinical history revealed 100% sensitivity with 45% specificity. Combination of PEFR and PC20 did not improve the diagnostic accuracy.

BOHRF Associated Evidence Statements

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

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3

Acceptable peak flow series can be obtained in around two thirds of those in whom a diagnosis of occupational asthma is being considered.

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3

The sensitivity and specificity of serial peak flow measurements are high in the diagnosis of occupational asthma

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Changes in non-specific reactivity at and away from work alone have only moderate sensitivity and specificity for diagnosis.