The Role of Inflammatory Markers in Predicting Autoimmune Comorbidities Among Patients with Type 1 Diabetes Mellitus

Background: Type 1 diabetes mellitus (T1DM) frequently coexists with other autoimmune diseases, which may enhance systemic inflammation and affect clinical outcomes. Novel inflammatory indices, including the pan-immune-inflammation value (PIV) and systemic immune-inflammation index (SII), have emerged as potential markers of immune activation. This study aimed to evaluate whether these markers could distinguish T1DM patients with comorbid autoimmune diseases from those without. Methods: In this retrospective analysis, patients with T1DM were stratified according to the presence or absence of comorbid autoimmune diseases. Demographic, metabolic, laboratory, and inflammatory parameters, including PIV, SII, and leukocyte subsets, were compared between groups using appropriate non-parametric tests. Results: Patients with autoimmune comorbidities exhibited significantly higher PIV (559.5 ± 390.5 vs. 225.5 ± 187.5, p<0.001) and SII (810.6 ± 407.7 vs. 503.1 ± 257.9, p<0.001) values compared with those without autoimmune conditions. Neutrophil and monocyte counts were also elevated (neutrophils: 5.7 ± 1.9 vs. 4.0 ± 1.3, p<0.001; monocytes: 0.68 ± 0.25 vs. 0.50 ± 0.14, p<0.001), whereas lymphocyte counts did not differ significantly (p=0.127). No statistically significant differences were observed in age, BMI, glycemic control (HbA1c: 8.7 ± 1.7% vs. 8.6 ± 1.6%, p=0.494), lipid profiles, or other standard laboratory parameters. Conclusion: Patients with T1DM and comorbid autoimmune diseases exhibit a markedly elevated inflammatory profile, as indicated by PIV and SII, despite having similar metabolic and demographic characteristics. These findings suggest that inflammatory indices may serve as adjunctive biomarkers for the detection or monitoring of autoimmune comorbidities in T1DM, warranting further prospective studies to evaluate their diagnostic and prognostic utility.