## 2 Materials and Methods  
Eighty patients were enrolled in this study (49 females and 31 males). All patients provided written informed consent and the study was approved by the University Ethic Committee (RNN/646/13/KB). Inclusion criteria (Table 1) were: physical status classification lower than 3, i.e., no severe systemic disturbances (American Society of Anesthesiologists Physical Status Classification System, ASA) orthognathic and minor traumatologic scheduled procedure, completed laboratory tests: alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, glycaemia, hemoglobin (Hb), chlorides (CI), potassium (K), sodium (Na), white blood cells count (WBC), CRP. Exclusion criteria: cardiovascular disease (anamnesis), kidney disease, i.e., glomerular filtration rate estimated with the use of the Modification of Diet in Renal Disease (MDRD) formula of estimated glomerular filtration rate (GFR-MDRD) in normal range and oncological issues (anamnesis). Serum suPAR level was measured in included cases with the use of the suPARnostic ELISA, ViroGates, Birkered, Denmark. The test was performed one day before surgical treatment. Laboratory parameters were analyzed in serum samples taken after fasting. After centrifugation, part of the serum was immediately aliquoted and frozen at \(-80\)\({}^{\circ}\)C for up to 10 months. For the suPAR analysis, the samples were thawed, thoroughly mixed and centrifuged, and their suPAR concentrations were assessed.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Age (years) & 30.25 \(\pm\) 9.65 \\ \hline Body Mass Index, BMI & 22.95 \(\pm\) 3.76 \\ \hline American Society of Anesthesiologists Physical Status & \\ Classification System, ASA & 1.23 \(\pm\) 0.50 \\ \hline Estimated Glomerular Filtration Rate using Modification of & \\ Diet in Renal Disease formula formula, GFR-MDRD & 107 \(\pm\) 19 \\ (mL/min/1.73 m) & \\ \hline Alanine transaminase, ALT (U/L) & 21 \(\pm\) 15 \\ \hline Aspartate transaminase, AST (U/L) & 22 \(\pm\) 10 \\ \hline Haemoglobin, Hb (g/dL) & 14.07 \(\pm\) 1.52 \\ \hline Albumin (g/L) & 47.88 \(\pm\) 3.08 \\ \hline Glycaemia (mmol/L) & 5.14 \(\pm\) 0.49 \\ \hline Chlorides (mmol/L) & 103 \(\pm\) 2 \\ \hline Potassium (mmol/L) & 4.29 \(\pm\) 0.29 \\ \hline Sodium (mmol/L) & 140 \(\pm\) 2 \\ \hline White Blood Cells count, WBC (Kcell/uL) & 4.631 \(\pm\) 2.167 \\ \hline Surgery duration (min) & 147 \(\pm\) 57 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of patients included in these studies.  
Next, Index of Body Inflammation (IBI) was calculated according to the equation below, to present the suPAR results in age-independent way [8]:  
\[\text{IBI}=1.223\sqrt[]{\frac{\text{suPAR}^{2}}{\log_{10}\text{Age}}} \tag{1}\]  
where age is in years and suPAR in ng/mL. Another suPAR, CRP test and IBI calculation were performed 3 days post-operationally, i.e., the day of hospital discharge. The healing process was monitored in patients for 6 months in an outpatient department. Postoperative complications were recorded.  
Data was analyzed with the use of Statgraphics Centurion 18 (Statgraphics Technologies Inc. The Plains City, VA, USA). Paired samples \(t\)-test was used for data collected pre- and post-operation in the same patient. Categorical data relation was investigated by independence \(\chi^{2}\) test. The relationship between the tested parameters and the occurrence of complications was studied with the use of one-way ANOVA. Relation between quantitative variable were analyzed with the use of linear regression. Level of significance was established as \(p<0.05\). Finally, factor analysis and an artificial neural network were used to determine the probability of any small complication to occur.