[Evaluation of the relationship between IL-18 levels in urine and parameters of renal pathological changes in patients with lupus nephritis].

Aim: To evaluate the relationship between IL-18 levels in urine and parameters of renal pathological changes in patients with lupus nephritis (LN).

Methods: IL-18 levels in morning free urine and 24-hour's urine in 19 normal persons and 55 patients with LN were measured by ELISA. The correlation between IL-18 levels and parameters of renal pathological changes, namely activity index (AI) and chronicity index (CI), were analyzed by liner correlation analysis method.

Results: IL-18 levels in morning free urine and 24-hour's urine in LN group were elevated significantly compared with control group. In both groups IL-18 levels in morning free urine were (247.1+/-317.5) ng/L and (20.3+/-14.5) ng/L, respectively, P<0.001; those in 24-hour's urine were (192.1+/-170.1) ng/d and (21.0+/-3.8) ng/d, respectively, (P<0.001). There was close positive correlation between IL-18 levels in morning free urine and 24-hour's urine and LN patient's AI (for morning free urine: r=0.602, P<0.001; for 24-hour's urine: r=0.461, P<0.005) but there was no correlation between IL-18 levels in morning urine and 24-hour's urine and CI (P>0.05). Patients with LN were divided into three groups (high, moderate and low) according to AI value. There was distinct difference of IL-18 levels in urine among the three groups: IL-18 levels in morning urine were (69.2+/-82.7) ng/L, (193.5+/-106.1) ng/L and (580.7+/-453.1) ng/L, respectively, (P<0.001); those in 24-hour's urine were (103.5+/-141.4) ng/d, (188.8+/-124.0) ng/d and (333.1+/-183.2) ng/d, respectively.

Conclusion: It is very simple and convenient to detect IL-18 levels in morning free urine, so it is a good method for evaluating renal pathological activity of LN.