Williams CEC, Toner A, Wright RD, et al. - Findings revealed that there are promising urine biomarkers for IgAV-N, some of which originate from the tubulointerstitial region, implying a pathophysiological role. Long-term assessment of these urine biomarkers is required to determine their actual potential as clinical practice adjuncts.

• A total of 121 studies were discovered, with 13 of them being suitable.

• In total, 2,446 paediatric patients were involved: healthy controls (n = 761), children with IgAV-N (n = 1236) and children with IgAV without nephritis (IgAV-noN, n = 449).

• Fifty-one percent were men, with a median age of 7.9 years.

• The clinical parameters, 24-hour protein amount and urine protein: creatinine ratio, were found adequate for evaluating nephritis severity (AUC < 0.8).

• Urinary albumin concentration (Malb) fared well (AUC 0.81–0.98).

• The following pre-clinical urinary biomarkers were shown to be the most promising in predicting the existence of nephritis: kidney injury molecule-1 (KIM-1) (AUC 0.93), monocyte chemotactic protein-1 (MCP-1) (AUC 0.83), N-acetyl-β-glucosaminidase (NAG) (0.76–0.96), and angiotensinogen (AGT) (AUC not available).

• KIM-1, MCP-1, and NAG levels in the urine were found to be related to disease severity.