Reliability and validity of the de Morton Mobility Index in individuals with sub-acute stroke

Abstract

Purpose: To establish the validity and reliability of the de Morton Mobility Index (DEMMI) in patients with sub-acute stroke.

Methods: This cross-sectional study was performed in a neurological rehabilitation hospital. We assessed unidimensionality, construct validity, internal consistency reliability, inter-rater reliability, minimal detectable change and possible floor and ceiling effects of the DEMMI in adult patients with sub-acute stroke.

Results: The study included a total sample of 121 patients with sub-acute stroke. We analysed validity (n = 109) and reliability (n = 51) in two sub-samples. Rasch analysis indicated unidimensionality with an overall fit to the model (chi-square = 12.37, p = 0.577). All hypotheses on construct validity were confirmed. Internal consistency reliability (Cronbach's alpha = 0.94) and inter-rater reliability (intraclass correlation coefficient = 0.95; 95% confidence interval: 0.92-0.97) were excellent. The minimal detectable change with 90% confidence was 13 points. No floor or ceiling effects were evident.

Conclusions: These results indicate unidimensionality, sufficient internal consistency reliability, inter-rater reliability, and construct validity of the DEMMI in patients with a sub-acute stroke. Advantages of the DEMMI in clinical application are the short administration time, no need for special equipment and interval level data. The de Morton Mobility Index, therefore, may be a useful performance-based bedside test to measure mobility in individuals with a sub-acute stroke across the whole mobility spectrum. Implications for Rehabilitation The de Morton Mobility Index (DEMMI) is an unidimensional measurement instrument of mobility in individuals with sub-acute stroke. The DEMMI has excellent internal consistency and inter-rater reliability, and sufficient construct validity. The minimal detectable change of the DEMMI with 90% confidence in stroke rehabilitation is 13 points. The lack of any floor or ceiling effects on hospital admission indicates applicability across the whole mobility spectrum of patients with sub-acute stroke.

Keywords: de Morton Mobility Index; mobility; outcome assessment; physiotherapy; stroke.