Turkish Validation of the Nijmegen Questionnaire in COPD

This single-center observational study will be conducted in patients with clinically stable COPD. The study consists of two main phases: (1) translation and cultural adaptation of the Nijmegen Questionnaire following international guidelines for patient-reported outcome measures, and (2) psychometric evaluation of the Turkish version in a COPD population. The translation process includes forward translation, reconciliation, back-translation, developer review, cognitive debriefing with patients, and final proofreading. After completion of the linguistic adaptation, the NQ-TR will be administered to eligible participants at baseline and repeated after one week in clinically stable individuals to assess test-retest reliability. Construct validity will be evaluated using exploratory and confirmatory factor analyses. Convergent validity will be assessed by examining correlations between NQ-TR scores and established clinical measures, including the COPD Assessment Test (CAT), Modified Medical Research Council (mMRC) Dyspnea Scale, Hospital Anxiety and Depression Scale (HADS), and Dyspnea-12 (D-12). Internal consistency, test-retest reliability, and measurement stability will be analyzed.