*3.3. Multiple Regression Analysis*

Multiple regression analysis identified five independent variables associated with circulating TBARS in CD patients; in contrast, the other oxidative stress biomarkers did not show significant associations with clinical parameters. By backward stepwise regression, TBARS were associated to the disease site, behavior, and first clinical presentation, being higher in patients with an ileal localization of the disease, with a fistulizing and stricturing behavior and with the severity of the first clinical presentation (combination of occlusion, anemia, and weight loss or the presence of perianal fistulas). Moreover, TBARS were also associated with the smoke habit and with the presence of allergies (Table 3). The oxidative score was associated with smoke habit (*p* = 0.013) and with the presence of a skin extension of the disease (*p* = 0.0245) (Table 4).


**Table 3.** Multiple regression analysis of factors associated with circulating TBARS in Crohn's patients.


**Table 4.** Multiple regression analysis of factors associated with the oxidative score in Crohn's patients.
