Capturing the patient's view of change as a clinical outcome measure

Context Measurement of change in patients' health status is central to both clinical trials and clinical practice. Trials commonly use serial measurem ents by the patients at 2 points in time while clinicians use the patient's retrospective assessment of change made at 1 point in time. How well these measures correlate is not known. Objective To compare the 2 methods in measurement of changes in pain and di sability. Design Longitudinal survey of patients starting new therapy for chronic art hritis in 1994 and 1995, Surveys were completed at baseline (before interve ntion) and at 6 weeks and 4 months. Setting Community health education program and university medical and ortho pedic services. Subjects A total of 202 patients undertaking self-management education (n = 140), therapy with prednisone or methotrexate; (n = 34), or arthroplasty o f the knee or hip (n = 28). Main Outcome Measures Concordance between serial (visual analog scale for p ain and Health Assessment Questionnaire for disability) and retrospective ( 7-point Likert scale) measures, sensitivities of these measures, and their correlation with patients' satisfaction with the change (7-point Likert sca le). Results When change was small (education group), serial measures correlated poorly with retrospective assessments (eg, r = 0.13-0.21 at 6 weeks). With greater change, correlations improved (eg, r = 0.45-0.71 at 6 weeks). Aver age agreement between all pairs of assessments was 29%. Significant lack of concordance was confirmed in all 12 comparisons by McNemar tests (P = .02 to < .001) and by 5 tests (P = .03 to < .001). Retrospective measures were more sensitive to change than serial measures and correlated more strongly with patients' satisfaction with change. Conclusion The 2 methods for measuring health status change did not give co ncordant results. Including patient retrospective assessments in clinical t rials might increase the comprehensiveness of information gained and its ac cord with clinical practice.