The Construct and Predictive Validity of the Japanese Version of the Intensive Care Unit Mobility Scale

Background/Objectives: The increasing emphasis on early mobilization in intensive care units (ICUs) has underscored the need for quick, simple, and reliable tools to assess patients' mobilization levels. The ICU Mobility Scale (IMS) was developed to address this need and has been translated into a Japanese version. This study aimed to evaluate the construct and predictive validity of the Japanese version of the IMS in critically ill patients. Methods: This was a secondary analysis of the EMPICS study, which included patients who stayed in ICUs for at least 48 h. The Japanese version of the IMS and physical function were assessed at ICU discharge. At hospital discharge, outcomes such as walking ability, discharge destination, activities of daily living (ADL) dependency, ICU-acquired weakness, and physical impairment were evaluated. At 90-day follow-up, the presence of post-intensive care syndrome (PICS) was assessed using quality of life scores, and mortality data were collected. Construct and predictive validity were analyzed using Spearman's rank correlation coefficients, the Mann-Whitney U test, and logistic regression analysis. Results: A total of 193 patients (mean age 68.2 years; 65.8% male) were included. The mean IMS score at ICU discharge was 5.6. The IMS score at ICU discharge showed significant correlations with the Barthel Index (ρ = 0.55, p = 0.001), Medical Research Council sum score (ρ = 0.45, p < 0.001), and grip strength (ρ = 0.44, p < 0.001), but not with body weight or sex. Logistic regression analyses demonstrated that a higher IMS score at ICU discharge was significantly associated with better physical outcomes at hospital discharge, a lower incidence of PICS, and reduced 90-day mortality. Conclusions: The Japanese version of the IMS demonstrated both construct and predictive validity in ICU patients. It is a useful tool for assessing daily mobilization levels in critical care settings. The findings may not be generalizable to all ICU patients due to the strict eligibility criteria.