38predictive Validity of a Severity Weighted Functional Comorbidity Index in Geriatric Rehabilitation

Background: In geriatric rehabilitation, functional prognosis informs expectations regarding recovery and discharge planning. Assessing pre-existent comorbidity may aid functional prognosis but existing indices have limitations in older populations. We investigated the predictive validity of the weighted Functional Comorbidity Index (wFCI) for recovery of mobility in an older cohort undergoing rehabilitation. Methods: Patients admitted to a community hospital for rehabilitation between January and September 2017 were recruited to an observational cohort study. Those admitted for end-of-life care were excluded. Outcome measures were: mobility at discharge assessed with the elderly mobility scale (EMS; range 0–20) and change in mobility (EMS gain/day). Comorbidity indices were collected at baseline: Charlson index (range 0–33), FCI (range 0–18) and wFCI (range 0–54). Univariate (Mann-Whitney U) and binary logistic regression analyses were performed. Variables were dichotomized around their median and 3 models were created to compare comorbidity indices. The wFCI classified comorbidity as: absent (0), and having no (1), partial (2) or severe (3) impact on function. Age, gender, basic activities of daily living (Barthel range 0–20) and cognitive function (MoCA range 0–30) at baseline were added to the models to control for confounding. Results: 75 patients (mean age 82 years; 61% female) were included. Median (IQR) Barthel index and MoCA were 9 (5) and 20 (10) respectively. Median EMS was 5 (4) and 11 (6) at admission and discharge respectively. Median (IQR) gain/day was 0.19 (0.25). Charlson and FCI did not independently contribute to the prediction models, but wFCI was associated with lower EMS at discharge (OR [95% CI]: 0.72 [0.54–0.93]) and lower EMS gain/day (OR: 0.80 [0.64–1.00]). Conclusion: The wFCI was independently predictive of mobility at discharge and mobility gain per day. Further research is required to understand how the wFCI can be incorporated into routine decision making in rehabilitation practice.