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Reliability of the de Morton Mobility Index (DEMMI) in an older acute medical population
Natalie A de Morton1, Megan Davidson, Jennifer L Keating
1School of Primary Health Care, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia; The Northern Clinical Research Center, Northern Health, Epping, Victoria, Australia. natalie.demorton@nh.org.au.
Background:
The de Morton Mobility Index (DEMMI) is an instrument that accurately measures the mobility of older people across clinical settings.
Purpose:
To report the multiple reliability studies conducted during the development and validation of the DEMMI.
Methods:
Intra-rater and inter-rater reliability studies were conducted for the DEMMI in two independent samples (development and validation samples) of older acute medical patients (aged 65 years or older). Inter-rater reliability studies were conducted between the test developer (a physiotherapist) and another experienced physiotherapist. Order of assessor administration was randomized by a coin toss. Patients who were fatigued after the first assessment were excluded from the inter-rater reliability study. Intra-rater reliability studies included participants with 'unchanged' mobility status between hospital admission and discharge. Scale reliability estimates were expressed as the minimal detectable change with 90% confidence (MDC90 ). Item reliability was calculated using Kappa statistics and absolute percentage agreement.
Results:
The MDC90 for the DEMMI development sample was 9.51 points (95% confidence interval [95% CI], 5.04-13.32; n=21) and 7.84 (95% CI, 4.34-11.65; n=16) on the 100-point interval DEMMI scale for the inter-rater and intra-rater reliability studies, respectively. Similar estimates were obtained for the DEMMI validation samples of 8.90 (95% CI, 6.34-12.69; n=35) and 13.28 points (95% CI, 8.08-20.87; n=19). Items were not excluded from the DEMMI based on the results of item reliability.
Conclusion:
Reliability estimates for the DEMMI were consistent across independent samples of older acute medical patients using different reliability study methodology. Error represents approximately 9% of the DEMMI scale width.
Insights
The de Morton Mobility Index (DEMMI) demonstrates reliable measurement of older adults' mobility. Its consistency across studies confirms its validity as a clinical assessment tool.
Area of Science:
- Gerontology
- Rehabilitation Medicine
- Clinical Assessment Tools
Background:
- The de Morton Mobility Index (DEMMI) is a validated instrument for assessing mobility in older adults within various healthcare settings.
- Accurate mobility assessment is crucial for effective geriatric care and rehabilitation planning.
Purpose of the Study:
- To comprehensively report the reliability studies conducted during the development and validation phases of the DEMMI.
- To provide evidence supporting the DEMMI's consistency and accuracy in measuring geriatric mobility.
Main Methods:
- The study involved intra-rater and inter-rater reliability assessments in two independent samples of older acute medical patients (≥65 years).
- Reliability was quantified using the minimal detectable change with 90% confidence (MDC90) for scale reliability and Kappa statistics/absolute percentage agreement for item reliability.
Main Results:
- Reliability estimates (MDC90) for the DEMMI were consistent across development and validation samples, with values ranging from 7.84 to 13.28 points.
- Item reliability analyses did not necessitate the exclusion of any items from the DEMMI scale.
- Error, representing approximately 9% of the DEMMI scale width, was consistent across different reliability study methodologies.
Conclusions:
- The DEMMI exhibits reliable measurement properties for assessing the mobility of older acute medical patients.
- The consistency of reliability estimates across independent samples and methodologies supports the DEMMI's utility in clinical practice.
- The DEMMI's error margin is quantifiable and represents a small fraction of the overall scale, indicating precision in measurement.
