Isolated Effects of Renal Failure, Anthropometric Indices, and Serum Total Iron-Binding Capacity as Determinants of Muscle Performance in Hemodialysis Patients.
OBJECTIVE
We quantified the isolated impact of end-stage renal disease (ESRD) on physical performance under contemporary hemodialysis treatment independent of comorbid diseases, characterized principal anthropometric components, and adjusted for their influence and compared associations of C-reactive protein (CRP), albumin, and serum total iron-binding capacity (TIBC) with muscle function.


DESIGN
A case-control cross-sectional study.


SETTING
University medical hospital and outpatient hemodialysis units.


SUBJECTS
Ninety prevalent hemodialysis patients without important comorbidities and 140 controls.


MAIN OUTCOME MEASURES
Handgrip strength (HGS) and 10-repetition sit-to-stand time (STS-10).


RESULTS
Principal component analysis revealed 3 representative anthropometric measures to be included in explanatory models of muscle performance additional to body height: lean body mass, fat mass, and joint size. Controlling for these covariates, age, sex, and residual comorbidity, ESRD was associated with a modest 7.5% reduction in HGS (B = -2.57 kg; 95% confidence interval: -4.81 to -0.39; P = .005; model R(2) 0.74) and a relatively larger prolongation of 27% in STS-10 time (B = 4s; 95% confidence interval: 2.61 to 5.4; P < .001; model R(2) 0.53). Lean body mass and height significantly predicted both tests, fat mass, and wrist size predicted HGS. In the subgroup of dialysis patients, only TIBC showed a significant association with HGS independently from age, sex, wrist size, whereas CRP and albumin did not. STS-10 time was not associated with any of these biomarkers. Results remained stable in sensitivity analyses excluding patients with reported chronic regional motor difficulties and aches.


CONCLUSIONS
ESRD with contemporary hemodialysis therapy has a relatively modest negative comorbidity-free association with HGS and a larger effect on STS-10 lower extremity performance. Nonmodifiable anthropometric indices (body height and for HGS wrist size) have a significant independent impact and should be consistently adjusted for in future studies. In low-comorbidity dialysis patients, TIBC is a superior predictor of HGS compared with albumin and CRP.