Predictive validity and interrater reliability of the German intensive care unit mobility scale (IMS)

BACKGROUND: Early mobilisation in the intensive care unit (ICU) is associated with improved patient outcomes. The Intensive Care Unit Mobility Scale (IMS) is established for rapid bedside assessment of patient mobilisation, but its predictive validity and interrater reliability have not been evaluated in German-speaking ICUs. METHODS: In a prospective, single-centre observational study, the German translation of the IMS was validated in a 21-bed anaesthesiology-led ICU. The IMS was assessed by nurses, physical therapists, residents and attending physicians, three times daily. Clinical endpoints included ICU and hospital length of stay (LOS), 90-day mortality, and functional outcomes at discharge (grip strength, Medical Research Council Sum Score (MRC-SS)). Interrater reliability (IRR) was calculated for the German IMS. RESULTS: A total of 100 patients were included. Higher mean IMS during ICU stay independently predicted shorter hospital LOS (Incidence Rate Ratio: 0.90, 95% CI (0.82, 0.95); p = 0.004) and lower 90-day mortality (Odds Ratio: 0.47; 95% CI (0.30, 0.74); p = 0.002). Higher discharge IMS correlated with improved functional outcomes (grip strength, MRC-SS), lower risk of ICU-acquired weakness (ICUAW), and reduced 90-day mortality. IRR was excellent, exceeding 0.95 across all professional categories. CONCLUSION: The German IMS demonstrates robust predictive validity and exceptional interrater reliability in a multiprofessional ICU setting. Both sustained mobilisation throughout the ICU stay and higher mobilisation at discharge are associated with shorter hospital stays, reduced mortality, and better functional recovery. These findings support routine integration of the IMS into ICU practice to guide targeted mobilisation strategies and improve patient outcomes.