Attributes and levels in discrete choice experiments for pharmacy services: A systematic review to inform asthma intervention design

Background: Asthma affects over 260 million people worldwide and remains poorly controlled. Pharmacists play an increasing role in management, yet evidence on which pharmacy service attributes patients value is limited. Objective: This review aimed to identify and synthesize the attributes and levels used in discrete choice experiments (DCEs) for patient-centered pharmacy interventions related to asthma. Methods: Following (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) PRISMA guidelines, PubMed, Scopus, and Google Scholar were searched for studies published from 1990 to 2025. Eligible studies included patients with asthma, caregivers, clinicians, or members of the general population reporting preference outcomes derived from DCEs or conjoint analyses (CA). Data on study characteristics, attribute development, pretesting, design, analytical models, and behavioral outcomes were extracted. Attributes were grouped into domains. Results: Of the 3287 records, seven studies met the inclusion criteria. Attributes clustered into symptoms, exacerbations, rescue medication use, treatment risks, device convenience, costs, and service processes. Clinical outcomes, especially symptom control and exacerbation prevention, were consistently prioritized. In contrast, pharmacy-specific attributes, including pharmacist counseling, private consultations, and continuity of care, were rarely included. Methodological quality varied, with limited patient involvement in attribute development and inconsistent pretesting procedures. Conclusion: Evidence emphasizes clinical outcomes rather than pharmacy service features in asthma-related DCEs. Future preference studies should incorporate pharmacy-relevant attributes and adopt more standardized, patient-informed methodologies to support patient-centered, pharmacist-led asthma interventions.