Reproducibility and Validity of the Dutch Translation of the de Morton Mobility Index (DEMMI) Used by Physiotherapists in Older Patients With Knee or Hip Osteoarthritis

Jans MP, Slootweg VC, Boot CR, de Morton NA, van der Sluis G, van Meeteren NL. Reproducibility and validity of the Dutch translation of the de Morton Mobility Index (DEMMI) used by physiotherapists in older patients with knee or hip osteoarthritis.ObjectiveTo examine the reproducibility, construct validity, and unidimensionality of the Dutch translation of the de Morton Mobility Index (DEMMI), a performance-based measure of mobility for older patients.DesignCross-sectional study.SettingRehabilitation center (reproducibility study) and hospital (validity study).ParticipantsPatients (N=28; age >65y) after orthopedic surgery (reproducibility study) and patients (N=219; age >65y) waiting for total hip or total knee arthroplasty (validity study).InterventionNot applicable.Main Outcome MeasuresNot applicable.ResultsThe intraclass correlation coefficient for interrater reliability was high (.85; 95% confidence interval, 71–.93), and minimal detectable change with 90% confidence was 7 on the 100-point DEMMI scale. Rasch analysis identified that the Dutch translation of the DEMMI is a unidimensional measure of mobility in this population. DEMMI scores showed high correlations with scores on other performance-based measures of mobility (Timed Up and Go test, Spearman r=−.73; Chair Rise Time, r=−.69; walking test, r=.74). A lower correlation of .44 was identified with the self-report measure Western Ontario and McMaster Universities Osteoarthritis Index.ConclusionsThe Dutch translation of the DEMMI is a reproducible and valid performance-based measure for assessing mobility in older patients with knee or hip osteoarthritis.