Stages of Kidney Function Based on Glomerular Filtration Rate (GFR)
Chronic kidney disease (CKD) is classified into five distinct stages based on glomerular filtration rate (GFR), with decreasing GFR values indicating progressive loss of kidney function. 1
The Five Stages of CKD Based on GFR
Stage 1: GFR ≥90 mL/min/1.73 m² with evidence of kidney damage (such as albuminuria, proteinuria, or structural abnormalities) 1
Stage 2: GFR 60-89 mL/min/1.73 m² with evidence of kidney damage 1
Stage 3: GFR 30-59 mL/min/1.73 m² (moderate decrease in kidney function); kidney damage markers not required for diagnosis at this stage 1
- Some guidelines further divide this into:
- Stage 3a: GFR 45-59 mL/min/1.73 m²
- Stage 3b: GFR 30-44 mL/min/1.73 m² 1
Stage 4: GFR 15-29 mL/min/1.73 m² (severe decrease in kidney function) 1
Stage 5: GFR <15 mL/min/1.73 m² or dialysis (kidney failure) 1
Clinical Significance of CKD Staging
The staging system has important clinical implications for patient management:
Stage 1-2: Focus on early detection, CKD risk reduction, and treating comorbid conditions 1
Stage 3: Requires estimating progression rate and beginning evaluation for complications 1
Stage 4: Intensive management of complications and preparation for possible kidney replacement therapy 1
Stage 5: Kidney replacement therapy (dialysis or transplantation) may be needed if uremic symptoms develop 1
Diagnostic Considerations
GFR should be estimated using prediction equations that account for serum creatinine, age, sex, race, and body size rather than relying on serum creatinine alone 1, 2
Common equations include the Modification of Diet in Renal Disease (MDRD) Study equation and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation 1, 3
For accurate diagnosis of CKD, abnormal GFR or kidney damage must persist for at least 3 months 1, 2
In stages 1 and 2, evidence of kidney damage (such as albuminuria) is required for CKD diagnosis, while stages 3-5 can be diagnosed based on GFR alone 1
Clinical Complications by CKD Stage
As GFR decreases below 60 mL/min/1.73 m², the risk of complications increases significantly 1
The prevalence of hypertension approaches 80% in patients with stage 4 CKD 1
Anemia becomes more prevalent as GFR falls below 60 mL/min/1.73 m² 1
The likelihood of having multiple complications (hypertension, anemia, hypoalbuminemia, hyperphosphatemia) increases substantially when GFR falls below 30 mL/min/1.73 m² 1
Important Caveats
GFR estimates may be less accurate at higher levels (>60 mL/min/1.73 m²), so clinical laboratories typically don't report numeric values above this threshold 1
In patients with sarcopenia, advanced cirrhosis, or other conditions affecting muscle mass, estimated GFR may be inaccurate and measured GFR might be necessary 4
For patients on dialysis, residual kidney function remains important and requires specialized approaches to assessment 5
The presence of proteinuria in diabetic patients supports a CKD diagnosis regardless of GFR values 1