Chronic kidney disease: the missing concept in the 2019 EULAR/ERA-EDTA recommendations for lupus nephritis

Chronic kidney disease (CKD) is diagnosed when glomerular filtration rate (GFR) falls below 60 mL/min/1.73 m2 or urinary albumin: creatinine ratio (UACR) reaches ≥ 30 mg/g, as these two thresholds indicate a higher risk of adverse health outcomes, including cardiovascular mortality. CKD is classified into mild, moderate or severe, based on GFR and UACR values, and the latter two convey a high or very high cardiovascular risk, respectively. Additionally, CKD can be diagnosed based on abnormalities detected by histology or imaging. Lupus nephritis (LN) is a cause of CKD. Despite the high cardiovascular mortality of patients with LN, neither albuminuria nor CKD are discussed in the 2019 EULAR-ERA/EDTA recommendations for the management of LN or the more recent 2022 EULAR recommendations for cardiovascular risk management in rheumatic and musculoskeletal diseases. Indeed, the proteinuria target values discussed in the recommendations may be present in patients with severe CKD and a very high cardiovascular risk that may benefit from guidance detailed in the 2021 ESC Guidelines on cardiovascular disease prevention in clinical practice. We propose that the recommendations should move from a conceptual framework of LN as an entity separate from CKD to a framework in which LN in considered a cause of CKD and evidence generated from large CKD trials applies unless demonstrated otherwise.