Chronic Kidney Disease Diagnosis and Staging

Definition and Classification

The National Kidney Foundation defines Stage 1 Chronic Kidney Disease (CKD) as kidney damage with a normal or increased glomerular filtration rate (GFR) of ≥90 mL/min/1.73 m², requiring evidence of kidney damage for at least 3 months 1, 2, 3
Kidney damage can be identified through proteinuria 2, hematuria 2, pathological abnormalities on kidney biopsy 4, or abnormalities in imaging tests 4

The current CKD classification system, as defined by the National Kidney Foundation, divides kidney disease into five stages based on GFR, with Stage 1: GFR ≥90 mL/min/1.73 m² with evidence of kidney damage 1, 3
Stage 2 is defined as GFR 60-89 mL/min/1.73 m² with evidence of kidney damage 1, 3
Stage 3 is characterized by a moderate decrease in GFR, with a GFR of 30-59 mL/min/1.73 m² 1, 3
Stage 4 is defined as a severe decrease in GFR, with a GFR of 15-29 mL/min/1.73 m² 1, 3
Stage 5 is characterized by kidney failure, with a GFR <15 mL/min/1.73 m² 1, 3

The diagnosis of CKD requires the presence of abnormalities for at least 3 months to differentiate from acute kidney injury, as recommended by the European Society of Cardiology 5
For Stages 1 and 2, evidence of kidney damage must be present in addition to the GFR criteria, according to the National Kidney Foundation 2, 4
For Stages 3-5, the GFR criteria alone are sufficient for diagnosis, regardless of evidence of kidney damage, as stated by the National Kidney Foundation 1, 3

Even Stage 1 CKD with normal GFR carries increased risk for cardiovascular disease and mortality, as reported by the American Heart Association 6
Early detection of CKD at Stage 1 allows for interventions that may slow progression to more advanced stages, as recommended by the National Kidney Foundation 6
Patients with Stage 1 CKD should be monitored for progression and managed for modifiable risk factors, according to the National Kidney Foundation 2

Relying solely on serum creatinine without calculating estimated GFR can lead to missed diagnoses, especially in elderly patients or those with reduced muscle mass, as warned by the National Kidney Foundation 7