Table 1 Construct validity of the de Morton Mobility Index (n = 153) including the hypotheses on construct validity and the constructs of the comparison measurement instruments
No. | Hypotheses | Comparison measurement instrument | Observed correlation with DEMMI (Spearman’s correlation) | Hypothesis confirmed | |||
|---|---|---|---|---|---|---|---|
Measurement instrument | Construct | Mean (SD) or median (IQR) | rho | 95% CI | |||
1 | Concerning 1-7, a correlation of > 0.7 was expected between the DEMMI and other broad measures of mobility and walking endurance | Hierarchical Assessment of Balance and Mobility, 0–26 points | Mobility | 14 ± 7 (0–26) | 0.95 | 0.93 to 0.96 | Yes |
2 | Performance Oriented Mobility Assessment, 0–28 points | Mobility | 7 (1–17) | 0.96 | 0.95 to 0.97 | Yes | |
3 | Functional Ambulation Categories, 0–5 points | Ambulation | 3 (0–4) | 0.92 | 0.89 to 0.94 | Yes | |
4 | Short Physical Performance Battery, 0–12 points | Physical functioning/mobility | 1 (0–5) | 0.93 | 0.91 to 0.95 | Yes | |
5 | Timed Up and Go test (n = 72), sec | Mobility | 23 ± 11 (10–63) | 0.70 | 0.56 to 0.80 | No | |
6 | Barthel Index mobility subscale, 0–40 points | Mobility | 15 (8–30) | 0.95 | 0.93 to 0.96 | Yes | |
7 | 2-min walk test (n = 88), meter | Walking endurance | 63 ± 29 (12–126) | 0.70 | 0.58 to 0.79 | No | |
8 | Concerning 7-8, a moderate correlation (0.5 < rho ≤ 0.7) was expected between the DEMMI and other single-component mobility scales | 4-m walk test (n = 85), m/s | Gait speed | 0.59 ± 0.23 (0.15–1.15) | 0.68 | 0.55 to 0.78 | Yes |
9 | 5× chair rise test (n = 28), sec | Lower limb strength | 18 ± 6 (9–34) | 0.63 | 0.35 to 0.80 | Yes | |
Hypotheses | Observed mean DEMMI scores (points) according to clinical groups | Statistical significance (Mann-Whitney U test, 1-fold) | Hypothesis confirmed | ||||
Clinical groups | DEMMI mean score | ||||||
10 | A statistically significant mean difference between ambulatory (FAC ≥ 3; n = 108) participants walking without versus participants walking with a walking aid. | No walking aid (n = 21) | 67 ± 7 (53–85) | U = 137; P < 0.01 | Yes | ||
Walking aid (n = 64) | 49 ± 11 (27–67) | ||||||
11 | A statistically significant mean difference between independently ambulatory (FAC ≥ 4) versus dependently ambulatory/non-ambulatory (FAC < 4) participants. | Independent walkers (n = 53) | 61 ± 9 (39–85) | U = 109; P < 0.01 | Yes | ||
Dependent/non-ambulatory (n = 100) | 27 ± 15 (0–57) | ||||||
12 | A statistically significant mean difference between participants who can perform the TUG and those who are not able to perform the TUG. | TUG possible (n = 72) | 56 ± 11 (36–85) | U = 115; P < 0.01 | Yes | ||
TUG not possible (n = 81) | 22 ± 13 (0–57) | ||||||
13 | A statistically significant mean difference between participants who can climb stairs and those who cannot. | Able to climb stairs (n = 51) | 61 ± 9 (39–85) | U = 96; P < 0.01 | Yes | ||
Not able to climb stairs (n = 102) | 27 ± 15 (0–57) | ||||||