Optimal Cutoff Values of Site-Specific Phase Angle for Predicting Independence in Activities of Daily Living in Post-stroke Patients.

BACKGROUND

Phase angle (PhA) is a potential indicator of nutritional status and functional outcomes. However, optimal regional PhA cutoff values for predicting activities of daily living (ADL) post-stroke are unclear. We aimed to determine these cutoffs and assess whether PhA adds prognostic value to established clinical models.

METHODS

In this retrospective cohort study, stroke patients undergoing inpatient rehabilitation had body composition and PhA measured via multi-frequency bioelectrical impedance analysis. The primary outcome was ADL independence at discharge (motor Functional Independence Measure >78). Receiver operating characteristic (ROC) curves identified optimal PhA cutoffs; logistic regression assessed their predictive value, adjusting for confounders. Incremental discriminative ability was evaluated using area under the ROC curve (AUC) comparisons with DeLong's test.

RESULTS

Among 1,080 patients (median age, 75.6 years; 54.1% men), optimal PhA cutoffs were: whole-body (women 3.90°, men 4.60°), non-paretic upper limb (4.45°, 4.90°), and non-paretic lower limb (4.00°, 4.80°). Higher PhA values above these cutoffs were independently associated with ADL independence (all p<0.05). Adding whole-body PhA to the baseline model improved AUC from 0.937 to 0.970 (ΔAUC=0.033; p=0.011); significant gains were observed for limb PhA.

CONCLUSIONS

Optimal site-specific PhA cutoffs predict ADL independence at discharge in post-stroke patients. PhA provides significant incremental prognostic value beyond established clinical models, supporting its use in tailoring rehabilitation strategies.