Oxidative stress is increasingly recognized as a significant contributor to the pathogenesis of inflammatory bowel disease (IBD). However, the clinical utility of oxidative stress-related biomarkers for assessing and predicting disease activity remains unclear. This prospective observational study aimed to evaluate the diagnostic and predictive performance of oxidative stress-related biomarkers in distinguishing between active IBD and remission across clinical, biochemical, and endoscopic criteria. A total of 76 patients with IBD were followed across three visits: baseline (biological treatment initiation), post-induction (6–12 weeks), and final follow-up (24–36 weeks). Associations with clinical, biochemical, and endoscopic remission status at the final follow-up were evaluated using correlation matrices, receiver operating characteristic curve analysis, principal component analysis, and logistic regression. Ceruloplasmin, plasma free thiols, gamma-glutamyl transferase, and albumin showed significant diagnostic values for distinguishing active disease from remission, using C-reactive protein (CRP)-based criteria. Serum uric acid, advanced oxidation protein products, gamma-glutamyl transferase, total antioxidant capacity, and ceruloplasmin predicted clinical or CRP-based remission when measured at baseline or post-induction, with predictive value varying by biomarker and the time point. Overall, our findings reinforce the role of oxidative stress in the pathogenesis of IBD and highlight the potential of oxidative stress-related biomarkers to be used as tools for monitoring disease activity and predicting IBD treatment outcomes.

Extracellular nanoparticles (EPs) are a subject of increasing interest for their biological role as mediators in cell–cell communication; however, their harvesting and assessment from bodily fluids are challenging, as processing can significantly affect samples. With the aim of minimizing processing artifacts, we assessed the number density (n) and hydrodynamic diameter (D_h) of EPs directly in diluted plasma and blood using the following recently developed technique: interferometric light microscopy (ILM). We analyzed 613 blood and plasma samples from human patients with inflammatory bowel disease (IBD), collected in trisodium citrate and ethylenediaminetetraacetic acid (EDTA) anticoagulants, and 163 blood and plasma samples from canine patients with brachycephalic obstructive airway syndrome (BOAS). We found a highly statistically significant correlation between n in the plasma and n in the blood only in the human (i.e., but not canine) blood samples, between the samples with trisodium citrate and EDTA, and between the respective D_h for both species (all p < 10⁻³). In the human plasma, the average <D_h> was 139 ± 31 nm; in the human blood, <D_h> was 158 ± 11 nm; in the canine plasma, <D_h> was 155 ± 32 nm; and in the canine blood, <D_h> was 171 ± 33 nm. The differences within species were statistically significant (p < 10⁻²), with sufficient statistical power (P > 0.8). For <n>, we found no statistically significant differences between the human plasma and blood samples or between the samples with trisodium citrate and EDTA. Our results prove that measuring n and D_h of EPs in minimally processed fresh blood and in diluted fresh plasma by means of ILM is feasible for large populations of samples.