Background: The utility of subjective measures of physical function as discriminative, evaluative and predictive tools in patients with ESRD is accepted, but objective performance tests also provide valuable information on patient status. The aims of this study were to determine what objective physical limitations exist in a select group of dialysis patients, designated as 'high-functioning' on the basis that they had low comorbidity and subjectively perceived themselves to function well, and to examine relationships between the objective and subjective measures.
Methods: Twelve patients (male, 7; female, 5) aged 18-55 years, with scores of > or = 75 points in the Short Form-36 Physical Function scale (PF) and low comorbidity (Charlson score < or = 2) were recruited for comparison with age and sex-matched sedentary controls. Objective performance measures included vibration perception threshold (VPT), peak quadriceps isokinetic and isometric muscle torque, time to reach peak isometric torque, balance (body sway with eyes open and closed), temporal gait parameters and the sit to stand test (STST).
Results: Dialysis patients demonstrated significant deficits by comparison with controls in subjective PF score (P < 0.001), VPT (P < 0.01), quadriceps isometric and isokinetic torque (P < 0.05, P < 0.005), body sway with eyes open (P < 0.01) and closed (P < 0.05), self selected (P < 0.005) and maximum (P < 0.01) walk speed, duration of gait cycle (P < 0.05) and STST (P < 0.001). There was significant agreement between the subjective PF score and VTP (P < 0.01), isokinetic torque (P < 0.05), body sway with eyes open (P < 0.05) and closed (P < 0.05), self-selected walk speed (P < 0.01) and STST (P < 0.01).
Conclusions: Subtle but significant deficits in subjective and objective physical function existed even in this select group of dialysis patients. These findings define in more detail the underlying neuromuscular impairments and support the early implementation of active targeted rehabilitation programmes. The subjective and objective measures used here offer a useful panel of tests for clinical use in high-functioning dialysis patients.