Use of Bioelectrical Impedance Analysis for the Measurement of Appendicular Skeletal Muscle Mass/Whole Fat Mass and Its Relevance in Assessing Osteoporosis among Patients with Low Back Pain: A Comparative Analysis Using Dual X-ray Absorptiometry.

STUDY DESIGN

Cross-sectional observational study.

PURPOSE

To compare measurements of appendicular skeletal muscle mass (ASMM) and whole fat mass (WFM) obtained using dualenergy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) among patients with low back pain (LBP). Moreover, the study investigated the correlation between BIA-based ASMM and DXA-based bone mineral density (BMD). Overview of the Literature: If reliable, BIA may be a useful alternative to DXA as a screening tool for sarcopenia and osteoporosis among patients with LBP.

METHODS

Measurements were performed in 130 patients, including BMD of the lumbar spine and femoral neck. The correlation between DXA and BIA as well as between BIA-ASMM and BMD were evaluated.

RESULTS

BIA and DXA were highly correlated in both male and female patients (r =0.73-0.90, p <0.0001). However, BIA consistently overestimated ASMM by 1.5-2.5 kg on an average (p <0.0001) and underestimated WFM (-4.0 to -2.7 kg) on an average (p <0.0001). BIA-based ASMM correlated with BMD of the lumbar spine in both male and female patients (r =0.28-0.37, p ≤0.02) and that of the femoral neck (r =0.34-0.51, p ≤0.005). Regarding the calculated skeletal muscle index (SMI: ASMM/height [m2]) used as a criterion for sarcopenia, BIA-based SMI correlated with BMD of the lumbar spine in male patients (r =0.44, p =0.0004) and that of the femoral neck in female patients (r =0.33, p =0.009).

CONCLUSIONS

BIA may be a favorable alternative to DXA as a screening tool for sarcopenia and osteoporosis among patients with LBP. Considering the overestimation of BIA-based ASMM and SMI, we recommend using the cutoff values for sarcopenia of 7.9 kg/m2 for males and 6.1 kg/m2 for females.