CMAJ • November 10, 2009; 181 (10). First published September 21, 2009; doi:10.1503/cmaj.080006
© 2009 Canadian Medical Association or its licensors
All editorial matter in CMAJ represents the opinions of the authors and not necessarily those of the Canadian Medical Association.
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Diagnosis of asthma in adults

Alan G. Kaplan, MD, Meyer S. Balter, MD, Alan D. Bell, MD, Harold Kim, MD and R. Andrew McIvor, MD MSc

From the Department of Family Practice (Kaplan) and the Department of Medicine (Balter), University of Toronto; the Department of Family Medicine (Bell), Humber River Regional Hospital, Toronto, Ont.; the Department of Medicine (Kim), University of Western Ontario, London, Ont.; the Fire-stone Institute for Respiratory Health (McIvor), St. Joseph’s Healthcare; and the Department of Medicine (McIvor), McMaster University, Hamilton, Ont.


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  		Table 1: Recommendation grades and levels of evidence for specific clinical actions*

 

Figure 119
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  		Box 1: Clinical features related to probability of asthma in those with episodic symptoms*

 

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  		Box 2: Alternative causes of symptoms suggestive of asthma*

 

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  		Table 2: Differences between asthma and chronic obstructive pulmonary disease (COPD)*

 

Figure 119
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  		Figure 1: Spirometry results for a patient with asthma: volume–time curves (A), flow–volume loops (B) and data table (C). Obstruction is indicated by the ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (55%); significant reversibility is indicated by the improvement in FEV1 after administration of bronchodilator (0.96 L or 53%). These results are diagnostic for asthma.

 

Figure 219
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  		Figure 2: Serial recordings of peak expiratory flow (PEF) for a patient with occupational asthma. Measurements made during periods at work and while off work show objective improvement of PEF while off work, particularly after 3–4 days (see lower panel). The asthma was due to inhalation of toluene diisocyanate present in a varnish that the patient used at work (exposure indicated by horizontal bars at top of graph). Arrows indicate use of reliever medication (salbutamol) for asthma symptoms. Reproduced courtesy of Dr. André Cartier and Medical Resource Communications. 47

 

Figure 319
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  		Figure 3: Bronchoprovocation challenge testing for occupational asthma for the same patient as depicted in Figure 2. The decrease in forced expiratory volume in 1 second (FEV1) after a 30-minute exposure to toluene diisocyanate (TDI; day B, October 27; rectangles) but not after a 30-minute control exposure to paint thinner (day A, October 21; triangles) indicates a positive result on this specific challenge test, providing further confirmation of the diagnosis of occupational asthma due to toluene diisocyanate. Testing was performed in a single-blind manner, with multiple spirometry measurements over time before and after exposure. For day A, FEV1 = 4.17 L, PC20 (concentration of the provoking agent that causes the FEV1 to drop by 20%) = 1.4. For day B, FEV1 = 4.16 L, PC20 = 0.66. Arrow indicates use of reliever medication (salbutamol). Reproduced courtesy of Dr. André Cartier and Medical Resource Communications. 47

 

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  		Figure 4: Diagnostic algorithm for asthma.

 

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  		Box 3: Contraindications to methacholine and exercise challenge testing53

 

Figure 419
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  		Box 4: Key messages for the diagnosis of asthma in adults