Patient-reported outcomes in internal medicine: Methodological considerations for valid measurement and...

Patient-reported outcome measures (PROMs) have become essential in contemporary internal medicine, where chronic, multisystem diseases and comorbidities make traditional biomedical endpoints insufficient as sole indicators of therapeutic benefit. PROMs capture symptom burden, functional capacity, emotional well-being, social participation and overall quality of life, thereby complementing laboratory indices, imaging findings and clinician-rated scales. Their growing use in regulatory evaluation, health technology assessment and value-based care underscores the need for rigorous methodology in their development, validation and interpretation. This review outlines key conceptual and practical issues that must be addressed for PROMs to provide valid, interpretable and clinically meaningful information. It emphasizes the central importance of a clearly articulated conceptual framework grounded in literature, clinical expertise and qualitative research with patients. It summarizes best practices in item generation and refinement, scaling and response options and the assessment of psychometric properties, including reliability, validity, responsiveness and interpretability. Particular attention is given to cross-cultural adaptation, differential item functioning and longitudinal measurement, which are crucial in heterogeneous internal medicine populations. The review also addresses the integration of PROMs into clinical trials and routine care, focusing on issues of feasibility, respondent burden, missing data and the translation of score changes into clinically actionable decisions. By clarifying these methodological foundations, it aims to support clinicians, investigators and policymakers in choosing, implementing and interpreting PROMs so that they genuinely reflect patients' experiences and priorities and thereby advance the practice of patient-centered internal medicine.