Validity and reliability of the de Morton Mobility Index in the subacute hospital setting in a geriatric evaluation and management population.

OBJECTIVE To investigate the clinimetric properties of the de Morton Mobility Index (DEMMI) in a Geriatric Evaluation and Management (GEM) population. DESIGN A longitudinal validation study (n = 100) and inter-rater reliability study (n = 29) in a GEM population. PATIENTS Consecutive patients admitted to a GEM rehabilitation ward were eligible for inclusion. METHODS At hospital admission and discharge, a physical therapist assessed patients with physical performance instruments that included the 6-metre walk test, step test, Clinical Test of Sensory Organization and Balance, Timed Up and Go test, 6-minute walk test and the DEMMI. Consecutively eligible patients were included in an inter-rater reliability study between physical therapists. RESULTS DEMMI admission scores were normally distributed (mean 30.2, standard deviation 16.7) and other activity limitation instruments had either a floor or a ceiling effect. Evidence of convergent, discriminant and known groups validity for the DEMMI were obtained. The minimal detectable change with 90% confidence was 10.5 (95% confidence interval 6.1-17.9) points and the minimally clinically important difference was 8.4 points on the 100-point interval DEMMI scale. CONCLUSION The DEMMI provides clinicians with an accurate and valid method of measuring mobility for geriatric patients in the subacute hospital setting.