Preserving reporting perspective when interpreting individual outcome changes.

This conceptual letter proposes treating changes in respondent or reporting perspective as changes in measurement conditions before interpreting consecutive outcome scores as individual improvement or deterioration. Patient self-report, proxy estimates of the patient's perspective, carers' own appraisals and clinician observations represent distinct sources. Catatonia provides an example of why clinical symptom ratings, patient-reported experience and health-related quality of life should remain separately identifiable, and why reliability does not establish score interchangeability. The letter recommends retaining source, perspective, instrument and administration details through clinical handover, documenting unavailable self-report and language assistance, and evaluating trajectories within consistent sources separately from source transitions. Independent paired reports could assess disagreement when feasible and proportionate. Proposed evaluation measures, including completion and transition frequencies, are candidates for testing, not validated indicators or evidence of improved outcomes.