Abstract
Psychometric. Assess the validity of bioimpedance-based measures of fat-free mass (FFM) in acute SCI and of current definitions of obesity based on body mass index (BMI). Australia. All admissions within eight weeks of a new traumatic SCI were screened. 29% were eligible. 71% of those consented. Twenty participants (18 male) completed deuterium dilution (DD) and bioimpedance-based measurements of FFM. Thirteen also underwent dual-energy x-ray absorptiometry. Strength of relationships and agreement were examined using Lin's concordance coefficient and limits of agreement analysis, respectively. Sensitivity and specificity were calculated for three BMI cutoffs for obesity, using percentage fat mass (%FM) obtained from DD as reference. Median time since injury was 41 days (IQR 28-48). FFM from DD and DXA were highly correlated but not identical. Concordance and agreement between DD and seven bioimpedance-based predictive equations are presented. The best-fitting equation demonstrated a low bias (+0.6 kg) and moderate dispersion (±5.2 kg). The cutoff for overweight in able-bodied people (BMI ≥25 kg/m2) provided sensitivity of 43.8%, compared to 25% for the cut-off for obesity (BMI ≥30 kg/m2). FM from bioimpedance gave the highest sensitivity (88.9%). BMI demonstrates poor specificity to classify obesity in acute SCI. Present findings support the utility of bioimpedance-based measurements for estimating FFM in acute SCI for group comparisons. These results are generalizable to traumatic SCI 4-8 weeks post injury; however, the present data reflect a high proportion of high cervical injuries. Further research is indicated to establish validity for assessment of individuals and for longitudinal monitoring. The present study was funded by a grant from the Institute for Safety, Compensation and Recovery Research (ISCRR Project #NGE-E-13-078). M Panisset was supported by an Australian Postgraduate Award. K Desneves was supported by the Austin Medical Research Foundation.
Highlights
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.The initial inflammatory response to traumatic injury triggers a catabolic process, whereby protein is scavenged from muscle tissues to support synthesis of critical visceral proteins
The aim of this study was to examine the validity of bioimpedance methods (BIA and Bioimpedance spectroscopy (BIS)) to assess fat-free mass (FFM) in acute spinal cord injury (SCI)
Highly correlated with deuterium dilution (DD) in this sample, Dual-energy x-ray absorptiometry (DXA) underestimated FFM by 2.9% with wide limits of agreement (LOA) (±11.5%). These findings indicate that DXA and doubly-labelled water (DLW) methods may be considered interchangeable within ±2.9% error margin for group means
Summary
The initial inflammatory response to traumatic injury triggers a catabolic process, whereby protein is scavenged from muscle tissues to support synthesis of critical visceral proteins. After spinal cord injury (SCI), initial neurologic and spinal shock are characterized by flaccid paralysis and physical activity is substantially limited. This combination of catabolism, paralysis and decreased activity precipitates rapid atrophy of muscle tissue. Loss of 33% of thigh muscle area occurs by six weeks post injury after incomplete SCI [1]. Up to 27–56%, occurs from 6–24 weeks in complete SCI [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
