What is Chronic Kidney Disease (CKD) staging?

From the Guidelines

Chronic Kidney Disease (CKD) should be staged based on both estimated glomerular filtration rate (eGFR) and albuminuria levels, as recommended by Kidney Disease: Improving Global Outcomes (KDIGO) 1. The staging of CKD is crucial for determining the prognosis and guiding treatment decisions.

• The eGFR categories define the stages of CKD, with Stage G1 and Stage G2 CKD defined by evidence of high albuminuria with eGFR ≥60 mL/min/1.73 m², and stages G3–G5 CKD defined by progressively lower ranges of eGFR 1.
• Additionally, the degree of albuminuria is associated with the risk of cardiovascular disease (CVD), CKD progression, and mortality, regardless of the eGFR level 1.
• The KDIGO recommends a comprehensive CKD staging system that incorporates albuminuria at all stages of eGFR, allowing for a more accurate assessment of disease severity and risk 1.
• This staging system is essential for clinicians to implement appropriate interventions at each stage to slow disease progression and improve patient outcomes. Key aspects of CKD staging include:
• eGFR categories: Stage G1-G5, with progressively lower ranges of eGFR
• Albuminuria categories: further refine risk assessment, with categories A1 (normal to mildly increased), A2 (moderately increased), and A3 (severely increased) 1
• Regular monitoring of kidney function, blood pressure control, and appropriate medication adjustments are essential across all stages to slow disease progression and improve patient outcomes.

From the Research

CKD Staging

• Chronic Kidney Disease (CKD) is defined as kidney damage or glomerular filtration rate (GFR) <60 mL/min/1.73 m(2) for 3 months or more, irrespective of cause 2
• Kidney disease severity is classified into five stages according to the level of GFR 2
• The Kidney Disease: Improving Global Outcomes (KDIGO) 2012 guidelines recommend classifying patients by GFR and albuminuria to predict CKD prognosis 3
• The KDIGO classification system includes five stages of CKD, based on the level of GFR, and three categories of albuminuria, which can help predict the risk of CKD progression and cardiovascular disease 3

Classification and Staging

• The K/DOQI definition and classification of CKD were accepted, with clarifications, and include a simple definition and classification system for CKD 2
• The KDIGO 2012 classification system is based on the level of GFR and the presence and severity of albuminuria 3
• The system includes five stages of CKD, based on the level of GFR, and three categories of albuminuria, which can help predict the risk of CKD progression and cardiovascular disease 3

GFR Estimation

• GFR can be estimated from calibrated serum creatinine and estimating equations, such as the Modification of Diet in Renal Disease (MDRD) Study equation or the Cockcroft-Gault formula 2
• The accuracy of GFR estimation is important for CKD staging and management 4

Albuminuria

• Albuminuria is defined as albumin-to-creatinine ratio >30 mg/g in two of three spot urine specimens 2
• The presence and severity of albuminuria can help predict the risk of CKD progression and cardiovascular disease 3
• Albuminuria is a key component of the KDIGO 2012 classification system, and is used to categorize patients into different risk groups 3