There is currently a lack of noninvasive biomarkers that effectively predict the progression of IgA nephropathy. We investigated the value of urinary IL-18 in predicting the progression of IgA nephropathy and whether its combination with clinical variables improved risk prediction. A total of 136 patients with IgA nephropathy were followed up for a median of 36 months in four academic medical centers. The levels of three biomarkers, urinary IL-18, urinary KIM-1 and urinary NGAL, were measured via ELISA in patients with 136 IgA nephropathy. The progression of IgA nephropathy was defined as a > 50% decrease in the eGFR or end-stage kidney disease. Multivariate Cox regression analyses of urine biomarkers for predicting the progression of IgA nephropathy were performed, and the AUCs of the clinical prediction models were calculated. Kaplan–Meier analysis revealed that high levels (> 28.1 pg/mg of creatinine) of urinary IL-18 were associated with a significantly poor renal outcome (P < 0.01), and Cox analysis further confirmed this result. High levels of urinary IL-18 were associated with a 4.7-fold greater risk for IgA nephropathy progression in adjusted analyses. For predicting IgA nephropathy progression, urinary IL-18 yielded a C-statistic of 0.77 (95% CI, 0.67–0.86), renal injury molecule 1 yielded 0.75 (95% CI, 0.65–0.86), and uNGAL yielded 0.70 (95% CI, 0.59–0.80). Urinary IL-18 levels significantly improved the C statistic from 0.77 to 0.89, outperforming the clinical and MEST-C scores. Urinary IL-18 is a significant predictor of poor renal outcomes and improves the risk prediction of IgA nephropathy.
Tang et al. (Mon,) studied this question.