Negative methacholine challenge tests in subjects who report physician-diagnosed asthma

• Published in: Clinical and experimental allergy Vol. 41; no. 1; pp. 46 - 51
• Main Authors: McGrath, K. W., Fahy, J. V.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2011; Blackwell; Wiley Subscription Services, Inc
• Subjects: Adolescent; Adult; Aged; Asthma; Asthma - diagnosis; Biological and medical sciences; brochoprovocation testing; Bronchial Provocation Tests - methods; Chronic obstructive pulmonary disease, asthma; diagnosis and assessment; Female; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; Indexing in process; Male; Medical sciences; Methacholine Chloride; Middle Aged; Physicians; Pneumology; Young Adult; Human; Lung disease; Agonist; Respiratory disease; Health staff; Methacholine chloride; Physician; Medical screening; Parasympathomimetic; Asthma; brochoprovocation testing; Cholinergic receptor; Immunology; Bronchus disease; Muscarinic receptor; Obstructive pulmonary disease; Diagnosis; diagnosis and assessment; Provocation test
• DOI: 10.1111/j.1365-2222.2010.03627.x
• ISSN: 0954-7894; 1365-2222

Summary Background The frequency of adults reporting a history of asthma is rising. However, it is unclear whether this increased prevalence accurately demonstrates a rising trend or if it reflects an overall increase in asthma awareness. Objective To determine the frequency of negative methacholine bronchoprovocation tests in adults who report physician‐diagnosed asthma and to explore the clinical characteristics of subjects with negative tests. Methods Data from methacholine challenge, spirometry, and physician assessment were analysed from 304 adults who reported physician‐diagnosed asthma and responded to community‐based advertising for asthma research studies. The clinical characteristics of methacholine‐positive and ‐negative subjects were compared and a predictive model was tested to identify those characteristics associated with a negative test. Results Of the 304 subjects tested, 83 (27%) had a negative methacholine test. A negative test was positively associated with an adult‐onset of symptoms (P<0.001), normal forced expiratory volume in 1 s (P<0.001), and having no history of exacerbation requiring oral steroids (P=0.03). Over half (60%) of those with a negative test reported weekly asthma‐like symptoms (cough, dyspnoea, chest tightness, or wheeze), while 39% reported emergency department visits for asthma‐like symptoms. Conclusions and clinical relevance A sizeable percentage of subjects who report physician‐diagnosed asthma have a negative methacholine challenge test. These subjects are characterized by diagnosis of asthma as an adult and by normal or near normal spirometry. Caution should be exercised in the assessment and diagnosis of adults presenting with asthma‐like symptoms, because they may not have asthma. Further diagnostic studies, including bronchoprovocation testing, are warranted in this patient group, especially if their spirometry is normal. Cite this as: K. W. McGrath and J. V. Fahy, Clinical & Experimental Allergy, 2011 (41) 46–51.