Clinical significance of the ratio of serum copper to zinc in patients with inflammatory bowel disease / 中华消化杂志

ABSTRACT

Objective:To explore the serum levels of copper and zinc and the application value of the ratio in assessing disease activity in patients with inflammatory bowel disease (IBD).Methods:From March 2019 to April 2020, 200 patients with IBD hospitalized at the Department of Gastroenterology of the First Affiliated Hospital of Anhui Medical University were selected by prospective random direct sampling method, including 100 patients with Crohn′s disease (CD) and 100 patients with ulcerative colitis (UC). The Crohn′s disease activity index (CDAI) and the modified Mayo score were used to evaluate the disease activity of CD patients and UC patients. In the same period 100 healthy individuals in the routine physical examination were selected as healthy control group. The serum levels of copper and zinc of the healthy control group, the CD group and the UC group were determined by atomic absorption spectrometry. The levels and the ratio of serum copper to zinc of three groups were compared. The ratio of serum copper to zinc of CD patients and UC patients with different disease activity were compared. The correlation between the ratio of serum copper to zinc and IBD activity indexes were analyzed, which included fecal calprotectin (FC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), CDAI and Mayo score. Receiver operating characteristic curve was drawn to analyze the value of the ratio of serum copper to zinc, CRP and ESR in predicting disease activity of patients with IBD. Independent sample t test, least significant difference- t test and Pearson correlation analysis were performed for statistical analysis. Results:The serum copper levels and the ratio of serum copper to zinc of the CD group and the UC group were both higher than that of the healthy control group, however the serum zinc levels were lower than that of the healthy control group ( (32.27±7.69) and (29.80±9.68) mol/L vs. (20.16±6.67) mol/L; 2.81±1.57 and 2.29±1.09 vs. 0.68±0.36; (14.64±7.11) and (15.65±8.17) mol/L vs. (34.29±16.40) mol/L), and the differences were statistically significant ( t=2.81, 5.87, 1.47, 7.21, 1.73 and 2.56, all P<0.05). Among CD patients, the the ratio of serum copper to zinc of patients at remission stage (29 cases), mild activity stage (23 cases), moderate activity stage (30 cases) and severe activity stage (18 cases) was 2.61±1.43, 2.75±1.35, 3.15±2.37 and 4.17±1.77, respectively, and the ratios of serum copper to zinc of patients at mild activity stage, moderate activity stage and severe activity stage were all higher than that of patients at the remission stage, and the differences were statistically significant ( t=3.41, 7.92 and 5.84, all P<0.05). There were statistically significant differences in the ratios of serum copper to zinc between patients at mild activity stage and moderate activity stage, severe activity stage, and between patients at moderate activity stage and severe activity stage ( t=5.82, 6.23 and 3.45, all P<0.05). Among UC patients, the ratio of serum copper to zinc of patients at remission stage (10 cases), mild activity stage (30 cases), moderate activity stage (45 cases) and severe activity stage (15 cases) was 1.52±0.44, 1.74±0.58, 2.38±0.83 and 3.80±1.19, respectively, the ratio of serum copper to zinc of patients at moderate activity stage was higher than that of patients at remission stage and mild activity stage, and the ratio of serum copper to zinc of patients at severe activity stage was higher than those of patients at remission stage, mild activity stage and moderate activity stage, and the differences were statistically significant ( t=7.92, 5.83, 3.21, 9.54 and 2.83, all P<0.05). There was no statistically significant difference in serum copper to zinc ratio between patients at remission and at mild activity stage ( P>0.05). The ratio of serum copper to zinc of CD patients was positively correlated with FC and CRP ( r=0.697 and 0.586, P=0.014 and 0.001), however was not correlated with ESR or CDAI score (both P>0.05). The ratio of serum copper to zinc of UC patients was positively correlated with FC, ESR and Mayo score ( r=0.488, 0.452 and 0.331, P=0.001, P<0.01 and P=0.041), however was not correlated with CRP ( P>0.05). The cut-off value of the ratio of serum copper to zinc, CRP and ESR for the diagnosis of CD activity was 1.76, 8 mg/L and 20 mm/1 h, respectively. Among them, ESR was the most effective in the diagnosis of CD activity with an area under the curve (AUC) value of 0.830, and to the sensitivity and specificity was 69.0% and 86.2%, respectively. The cut-off value of the ratio of serum copper to zinc, CRP and ESR for the diagnosis of UC activity was 1.63, 8 mg/L and 20 mm/1 h, respectively; among which the the ratio of serum copper to zinc had the highest efficacy in the diagnosis of UC activity, with an AUC value of 0.862, sensitivity and specificity of 73.0% and 90.9%, respectively. Conclusion:The the ratio of serum copper to zinc is correlated with the disease activity of IBD, which may become a new auxiliary indicator for the evaluation of disease activity.