Reliability, validity, sensitivity and internal consistency of the ICF based Basic Mobility Scale for measuring the mobility of patients with musculoskeletal problems in the acute hospital setting: a prospective study

BACKGROUND: The assessment of mobility is important in the acute care setting. Existing tests suffer from limitations. The aim of the study was to examine the inter-rater reliability, the validity, the sensitivity to change, and the internal consistency of an ICF based scale. METHODS: In a prospective study inpatients in the acute care setting with restricted mobility aged above 50 years assigned to rehabilitative treatment were included. Assessment of subscales of the Functional Independence Measure (FIM) and the ICF based Basic Mobility Scale (BMS) were performed at admission and before discharge. Furthermore pain, length of stay in hospital, and post-discharge residential status were recorded. Inter-rater reliability, criterion-concurrent validity, sensitivity to change, and internal consistency were calculated. Furthermore, floor and ceiling effects were determined. RESULTS: One hundred twenty-five patients (79 women/46 men) were included. The BMS showed an excellent inter-rater reliability for the total BMS (ICC BMS: 0.85 (95 % CI: 0.81–0.88). The criterion-concurrent validity was high to excellent (Spearman correlation coefficient: −0.91 in correlation to FIM) and the internal consistency was good (Cronbach’s alpha 0.88). The BMS proved to be sensitive to improvements in mobility (Wilcoxon’s signed rank test: p < 0.0001; The effect size for the BMS was 1.075 and the standardized response mean 1.10. At admission, the BMS was less vulnerable to floor effects. CONCLUSIONS: The BMS may be used as a reliable and valid tool for the assessment of mobility in the acute care setting. It is easy to apply, sensitive to change during the hospital stay and not vulnerable to floor and ceiling effects. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12891-015-0638-7) contains supplementary material, which is available to authorized users.