BACKGROUND: In renal studies, various outcome endpoints are used with variable definitions, making it nearly impossible to perform meta-analyses and deduce meaningful conclusions. Increasing attention is directed towards standardization of renal outcome reporting.

METHODS: A working group was formed to produce a unifying definition of renal outcomes that can be used by all investigators. We propose major adverse renal events (MARE) as the term for a standardized composite of hard renal outcomes. We discuss the components for inclusion in MARE from existing evidence.

RESULTS: MARE could include three to five items, considered relevant to patients and regulators. New onset of kidney injury, that is persistent albuminuria/proteinuria and/or decreasing glomerular filtration rate (GFR) <60 ml/min/1.73 m2, persistent signs of worsening kidney disease, development of end-stage kidney disease with estimated GFR <15 ml/min/1.73 m2 without or with initiation of kidney replacement therapy, and death from renal cause are core items of MARE. Additionally, patient reported outcomes should be reported in parallel to MARE as a standard set of primary (or secondary) endpoints in studies on kidney disease of diabetic, hypertensive-vascular, or other origin.

CONCLUSIONS: MARE as a reporting standard will enhance the ability to compare studies and thus, facilitate meaningful meta-analyses. This will result in standardized endpoints that should result in guideline improvement to better individualize care of patients with kidney disease.