Frequency and determinants of exaggerated bronchoconstriction during shortened methacholine challenge tests in epidemiological and clinical set-ups

The European Respiratory Society guidelines on bronchial provocation testing have proposed time-saving procedures, which may lead to unwanted exaggerated responses. The frequency and determinants of exaggerated bronchoconstriction in response to methacholine inhalation testing in clinical and epidemiological settings have not been assessed. The authors evaluated: 1) the prevalence of exaggerated bronchoconstriction, 2) its relation to time-saving measures (starting methacholine concentration and skipping concentrations); and 3) associations between such reactions and risk factors, respiratory symptoms and/or lung function parameters. Clinical (n=408) and epidemiological (n=711) groups were included. Exaggerated bronchoconstriction was defined as either a fall greater than or equal to 20% following saline or a greater than or equal to 30% fall in forced expiratory volume in one second (FEV1) after methacholine inhalations. Cases were compared with two groups of subjects: 1) with measurable bronchial responsiveness (MBR); and 2) without MBR. In the epidemiological group, 84 subjects (12%) presented exaggerated bronchoconstriction. Skipped concentrations accounted for an exaggerated bronchoconstriction in 18 of these. In the clinical group, 41 subjects (10%) experienced exaggerated reactions. Skipped concentrations accounted for an exaggerated bronchoconstriction in five of these. The provocative concentration of methacholine causing a 20% fall in FEV1 values were marginally lower in subjects with exaggerated bronchoconstriction. Questionnaire analysis in epidemiological subjects showed some symptoms of asthma and rhinitis to be more prevalent in cases than in subjects without MBR, In conclusion, methacholine? inhalation tests with time-saving measures result in a 10% risk of exaggerated bronchoconstriction as defined in this study and bronchial responsiveness is more prominent in subjects with exaggerated bronchoconstriction.