To analyze the diagnostic value of interleukin-6 (IL-6) and complement 1q (C1q) in acute ulcerative colitis and their correlation with gut microbiota.

A total of 120 patients with ulcerative colitis (UC) admitted to Yulin Traditional Chinese Medicine Hospital from January 2022 to March 2025 were selected as the study group. According to the modified Mayo score, they were divided into an acute phase group (n=62) and a remission phase group (n=58). During the same period, 60 healthy examinees were selected as the control group. By comparison of the changes in serum IL-6, C1q, and gut microbiota among different groups, logistic regression analysis was used to explore the effects of serum IL-6 and C1q on the progression of UC disease. Receiver operating characteristic curves (ROC) were plotted to analyze the diagnostic value of serum IL-6 and C1q for acute ulcerative colitis, and Pearson test was used to analyze the correlation between serum IL-6, C1q, and gut microbiota count.

There were statistically significant differences (P<0.05) in the levels of serum IL-6, C1q, and major gut microbiota (Bifidobacterium, Lactobacillus, Bacteroidetes, Escherichia coli, and Enterococcus) among the three groups. Among them, serum IL-6, Bacteroidetes, Escherichia coli, and Enterococcus gradually increased in the control group, remission group, and acute group (P<0.05); Serum C1q, Bifidobacterium, and Lactobacillus gradually decreased in the control group, remission group, and acute group (P<0.05). According to logistic regression analysis, serum IL-6 and C1q were important factors affecting the staging of UC disease activity (P<0.05). ROC curve analysis showed that serum IL-6 and C1q could predict the progression of UC disease, with the best combined efficacy (P<0.05). The area under the curve (AUC), sensitivity, and specificity were 0.931 (95% CI: 0.854-0.977), 89.4%, and 75.8%, respectively. Pearson correlation analysis showed that serum IL-6 was positively correlated with Bacteroidetes, Escherichia coli, and Enterococcus (P<0.05), and negatively correlated with Bifidobacterium and Lactobacillus (P<0.05); Serum C1q was inversely proportional to Bacteroidetes, Escherichia coli, and Enterococcus (P<0.05), and directly proportional to Bifidobacterium and Lactobacillus.

Serum IL-6 and C1q can predict the occurrence of acute UC, with the former being positively correlated with Bacteroidetes, Escherichia coli, and Enterococcus, and the latter being positively correlated with Bifidobacterium and Lactobacillus.