Polypharmacy Interactions Impacting Methacholine Challenge Testing for Asthma Assessment in Older People

Objective To investigate potential reasons for unusually high incidence of negative Methacholine Challenge Tests (MCT), following standardized MCT medication-hold protocol, in older people with physician-diagnosed asthma. Design An analysis of a longitudinal
 observational parent study of asthma. Setting Community-dwelling participants were evaluated in an outpatient clinic and at home. Participants Screening inclusion criteria for the parent study included 60 years of age or older, physician diagnosis of
 asthma, and a positive response to at least one of six asthma screening questions. Participants were enrolled in the study if they also demonstrate either: (1) a postbronchodilator administration response showing an increase of at least 12% and 200 mL in forced expiratory volume or an increase
 of at least 12% and 200 mL in forced vital capacity, or (2) an MCT result of PC20 ≤ 16 mg/mL (indicating bronchial hyper-responsiveness, MCT positive). Exclusion criteria included diagnosis of cognitive impairment or dementia, residing in a long-term care facility, more than 20 pack/ year
 smoking history or a history of smoking within the previous five years, inability to perform pulmonary function testing maneuvers, and a Prognostic Index score of greater than 10. Interventions Analysis of participant data for non-medication- and medication-exposure factors
 for association with negative MCT results. Results Anticholinergic burden and statin use were positively associated with negative MCT. Conclusion Medications not accounted for in medication-hold protocols, and concurrently in use, may impact clinical
 tests and outcomes.