Expression of interleukin-18 in patients with renal damage induced by ANCA-associated small vasculitis and its clinical significance

Objective To investigate the possible value of interleukin-18 (IL-18) in the application of renal damage induced by ANCA associated small vessel vasculitis (AASV). Methods The levels of serum and urine IL-18 were compared between control group and AASV group, or between AASV active group and remission group. The correlation between urine IL-18 and other clinical indicators such as serum ANCA, creatinine, C-reactive protein (CRP) and BVAS score was analyzed. In combining with ROC curve of urine IL-18 in determining the activity of AASV, the significance of IL-18 in AASV renal damage was evaluated. Results The levels of urinary IL-18 in the AASV group were significantly higher than those in the control group (P<0.05), and the active AASV group had a higher expression of urine and serum IL-18 than the remission group (P<0.05). Six months after treatment, urinary IL-18 levels in patients whose disease was changed from activity to remission were significantly decreased (P<0.05). Urinary IL-18 in AASV patients was positively correlated with serum ANCA and BVAS score (P<0.05), but had no significantly liner correlation with creatinine, serum cystatin C, C-reactive protein, urinary albumin/creatinine ratio and β₂-microglobulin. Serum and urine IL-18 had a positive correlation in AASV active group (P<0.05). The area under the ROC curve for urine IL-18 in diagnosis of renal damage in AASV was 0.816 (P<0.05), when the cut-off value was 0.130 pg·mL^-1·Cr^-1, the sensitivity and specificity were 85.7% and 71.4% respectively. Conclusions The levels of urinary IL-18 were elevated in patients with renal impairment of AASV and correlated with disease activity. Urinary IL-18 had a certain value in the early prediction of AASV disease activity.