## 3 Results
### Body Composition
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Groups** & \begin{tabular}{c} **T Score** \\ **L1–L4** \\ \end{tabular} & \begin{tabular}{c} **Z Score** \\ **L1–L4** \\ \end{tabular} & \begin{tabular}{c} **T Score** \\ **L1–L4** \\ \end{tabular} & \begin{tabular}{c} **T Score** \\ **Neck** \\ \end{tabular} & \begin{tabular}{c} **Z Score** \\ **Neck** \\ \end{tabular} & \
\begin{tabular}{c} **T Score** \\ **Total Body** \\ \end{tabular} &
\begin{tabular}{c} **Z Score** \\ **Total Body** \\ \end{tabular} \\ \hline
**SLE OPIA** & \(-2.17\pm 0.71\) & \(-1.88\pm 1.20\) & \(-1.50\pm 0.83\) & \(-0.93\pm 0.61\) & \(-1.16\pm 0.89\) & \(-0.90\pm 0.69\) \\
**SLE** & \(0.10\pm 0.73\) & \(-0.03\pm 0.31\) & \(-0.08\pm 1.11\) & \(0.24\pm 0.60\) & \(0.72\pm 0.87\) & \(0.39\pm 0.59\) \\
**CG** & \(-0.09\pm 1.37\) & \(-0.03\pm 1.16\) & \(-0.24\pm 1.20\) & \(0.26\pm 1.03\) & \(0.29\pm 1.14\) & \(0.19\pm 0.90\) \\ \(p\)**value** & \(<0.0001\) & 0.0006 & 0.0179 & 0.0038 & 0.0018 & 0.0035 \\ \hline \end{tabular}  
* ASMM = appendicular skeletal muscle mass (arms + legs); BF% = body fat percentage; BMI = body mass index (weight/height2); FMI = fat mass index (total body fat/height2); SMI = skeletal mass index (ASMM/height2), SLE OPIA—SLE individuals with OPIA, SLE—individuals without OP or OPIA, CG—non-lupus individuals. Statistical test: ANOVA, \(p\) < 0.05. Data are presented in mean \(\pm\) SD.  
As demonstrated in Figure 4, it is possible to observe that of the three ROIs included in the analysis, the group SLE OPIA showed a lower BMD in the lumbar segment compared to the other two groups, as expected.  
\end{table} 
Table 2: DXA bone, lean and fat tissues results according to each group. The mean lumbar BMD was 0.925 \(\pm\) 0.075 g/cm\({}^{2}\) for SLE OPIA, 1.226 \(\pm\) 0.115 g/cm\({}^{2}\) for SLE and 1.184 \(\pm\) 0.172 g/cm\({}^{2}\) for CG (\(p\) 0.001). The mean femur neck BMD was 0.844 \(\pm\) 0.098 g/cm\({}^{2}\) for SLE OPIA, 1.020 \(\pm\) 0.129 g/cm\({}^{2}\) for SLE and 1.006 \(\pm\) 0.165 g/cm\({}^{2}\) for CG (\(p\) = 0.0332). The mean total body BMD was 1.045 \(\pm\) 0.061 g/cm\({}^{2}\) for SLE OPIA, 1.198 \(\pm\) 0.064 g/cm\({}^{2}\) for SLE and 1.148 \(\pm\) 0.091 g/cm\({}^{2}\) for CG (\(p\) = 0.0018). In Table 2, the lean and fat tissue composition of the three groups can be observed, with several indexes used to analyze obesity and sarcopenia [30]. No significant differences in the calculations for each group were found, all the participants being similar in fat and lean tissue composition, albeit the low bone mass of SLE OPIA group. The BMI of the three groups demonstrated no obese subjects, only overweight, for the three groups (\(<\)30 kg/m\({}^{2}\)). That finding was different from BF% and FMI. BF% was above 43% for all patients; according to this index, all the participants were obese, but the mean FMI suggested overweight for SLE OPIA (\(<\)13 kg/m\({}^{2}\)) and class I obesity for SLE and CG (\(>\)13 kg/m\({}^{2}\)). The BMI and the SMI were correlated as expected in SLE OPIA (\(r\) = 0.892; \(p\) = 0.003) and CG (\(r\) = 0.939; \(p\) = 0.001) groups, but not for SLE (\(r\) = 0.595; \(p\) = 0.09). None of the three groups demonstrated sarcopenia (\(\Delta\)SMI \(>\) 5.5 kg/m\({}^{2}\)), but the BMD L1-L4 was significantly negatively correlated to SMI for SLE OPIA (\(r\) = \(-\)0.759; \(p\) = 0.029).