Letter to the Editor Regarding “Comparative Effectiveness of FF/UMEC/VI and BUD/GLY/FORM in Patients with COPD Stepping Up From Dual Therapy”

We read with interest the manuscript by Wedzicha and colleagues [1] that reports on a comparison of real-world effectiveness of singleinhaler triple therapies (SITT) in patients with COPD escalating from dual therapy.The authors suggest differences in effectiveness of SITT with 18% reduction in recorded COPD exacerbations with fluticasone furoate/umeclidinium/ vilanterol (FF/UMEC/VI) compared with budesonide/glycopyrrolate/formoterol fumarate (BUD/GLY/FORM).However, we would like to highlight important areas that may aid in the interpretation of these comparative effectiveness results: (1) the limitations inherent to open claims data and (2) the inclusion of early adopters of BUD/GLY/FORM.This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors. LIMITATIONS OF USING OPEN INSURANCE CLAIMS DATA FOR COMPARATIVE ANALYSESThe use of open claims data is typically driven by their strength, such as large sample size and diversity.However, there are notable limitations in data quality that apply to studies relying on open claims databases.They lack direct verification of insurance eligibility and may include overlapping records, inconsistent capture of encounters, and incomplete longitudinal follow-up.Unlike closed claims datasets, which reflect continuous enrollment