Long-term prediction of functional independence using adjusted and unadjusted single items of the functional independence measure (FIM) at discharge from rehabilitation

Context: Being able to survive in the long-term independently is of concern to patients with spinal cord injury (SCI), their relatives, and to those providing or planning health care, especially at rehabilitation discharge. Most previous studies have attempted to predict functional dependency in activities of daily living within one year after injury.

Objectives: (1) build 18 different predictive models, each model using one FIM (Functional Independence Measure) item, assessed at discharge, as independent predictor of total FIM score at chronic phase (3-6 years post-injury) (2) build three different predictive models, using in each model an item from a different FIM domain with the highest predictive power obtained in objective (1) to predict "good" functional independence at chronic phase and (3) adjust the 3 models from objective (2) with known confounding factors.

Methods: This observational study included 461 patients admitted to rehabilitation between 2009 and 2019. We applied regression models to predict total FIM score and "good" functional independence (FIM motor score ≥ 65) reporting adjusted R², odds ratios, ROC-AUC (95% CI) tested using 10-fold cross-validation.

Results: The top three predictors, each from a different FIM domain, were Toilet (adjusted R² = 0.53, Transfers domain), Toileting (adjusted R² = 0.46, Self-care domain), and Bowel (adjusted R² = 0.35, Sphincter control domain). These three items were also predictors of "good" functional independence (AUC: 0.84-0.87) and their predictive power increased (AUC: 0.88-0.93) when adjusted by age, paraplegia, time since injury, and length of stay.

Conclusions: Discharge FIM items accurately predict long-term functional independence.