Patient and Therapist Agreement on Performance-Rated Ability Using the de Morton Mobility Index

Abstract

ObjectiveTo determine the level of agreement between patient self-report and therapist-assessed performance of mobility using the de Morton Mobility Index (DEMMI). DesignInterrater agreement study. SettingOutpatient hospital clinic. ParticipantsConsecutive sample of patients (N=128) undergoing preoperative assessment for elective lower limb (LL) arthroplasty. InterventionsParticipants completed a therapist-directed assessment of the DEMMI followed by self-report of performance. A random subsample (n=62, 48%) also completed a self-report of anticipated performance before the therapist-directed assessment. Both raters (participant and therapist) were blinded to the scores obtained from the other rater. Main Outcome MeasuresInterrater agreement between patient self-report and therapist-directed assessment of the total DEMMI scores was assessed using the intraclass correlation coefficient model 2,1 (ICC2,1) with a 95% confidence interval. The Bland-Altman plots were also used to illustrate the agreement between the 2 raters. ResultsThe intraclass correlation coefficient (ICC) between patient self-report after performance and therapist-directed assessment of the total DEMMI score was .967 (95% confidence interval, .952–.977). The ICC between patient self-report of anticipated performance and therapist-directed assessment of the total DEMMI score was .830 (95% confidence interval, .730–.894). The Bland-Altman plots depicted higher levels of agreement among participants with impaired levels of mobility (≤74 out of 100) than did those with near-maximum DEMMI scores. ConclusionsPatient self-report of anticipated performance is an acceptable proxy for DEMMI scores derived from the therapist rating of performance. Caution should be exercised when interpreting self-report scores of patients with near-maximum levels of mobility. Further research is required to establish whether these results can be generalized across a range of patient populations and to clinicians with differing backgrounds and expertise.