How can an estimated Glomerular Filtration Rate (eGFR) between 60 and 90 mL/min/1.73 m² be considered normal when it is classified as Chronic Kidney Disease (CKD) stage 2?

Understanding eGFR Reference Ranges and CKD Classification

The Critical Distinction: Normal Function vs. CKD Diagnosis

An eGFR between 60-90 mL/min/1.73 m² can only be classified as CKD Stage 2 when there is documented evidence of kidney damage present for at least 3 months—without such evidence, this range does not represent CKD at all. 1

The confusion you've encountered stems from a fundamental misunderstanding of how CKD is defined. The staging system requires two separate components to be evaluated:

The Two-Part Diagnostic Criteria

For CKD Stages 1 and 2, evidence of kidney damage MUST be present in addition to the GFR criteria. 1 This is the key point that resolves your question.

• Stage 1 CKD: eGFR ≥90 mL/min/1.73 m² WITH evidence of kidney damage 2, 1
• Stage 2 CKD: eGFR 60-89 mL/min/1.73 m² WITH evidence of kidney damage 2, 1
• Stage 3 and beyond: eGFR <60 mL/min/1.73 m² alone is sufficient for CKD diagnosis, regardless of whether kidney damage markers are present 2, 1

What Constitutes "Kidney Damage"?

Evidence of kidney damage includes: 2, 1

• Proteinuria/albuminuria: Albumin-to-creatinine ratio (UACR) ≥30 mg/g 2
• Hematuria: Persistent blood in urine 1
• Pathological abnormalities: Findings on kidney biopsy 1
• Imaging abnormalities: Structural changes on ultrasound or other imaging 1

These abnormalities must persist for at least 3 months to differentiate CKD from acute kidney injury. 1, 3

Why Your Lab Changed the Reference Range

The Shift from ≥90 to ≥60 mL/min/1.73 m²

Your laboratory likely changed its "normal" reference range from ≥90 to ≥60 mL/min/1.73 m² because below 60 mL/min/1.73 m² represents loss of half or more of normal adult kidney function, and this threshold marks where complications of CKD significantly increase. 2

This change reflects the clinical reality that:

• eGFR 60-89 mL/min/1.73 m² WITHOUT kidney damage markers is NOT considered CKD 2, 1
• eGFR <60 mL/min/1.73 m² alone is sufficient to diagnose CKD (Stage 3 or higher), even without other markers of damage 2, 1
• The risk of cardiovascular mortality and other adverse outcomes increases exponentially when eGFR falls below 60 mL/min/1.73 m² 2

Age-Related Considerations

Normal GFR physiologically decreases with age, and in adults older than 70 years, values below 60 mL/min/1.73 m² could be considered normal in the absence of kidney damage markers. 4 This creates additional complexity:

• Young adults typically have GFR of 120-130 mL/min/1.73 m² 2
• GFR declines with age as part of normal aging 2, 4
• Approximately 17% of persons older than 60 years have eGFR <60 mL/min/1.73 m² 2

However, even age-related decline in eGFR remains an independent predictor of adverse outcomes including death and cardiovascular disease, which is why the CKD definition remains the same regardless of age. 2

Clinical Implications of the 60-89 mL/min/1.73 m² Range

When It IS CKD Stage 2

If you have eGFR 60-89 mL/min/1.73 m² AND any of the following: 1

• Persistent proteinuria (UACR ≥30 mg/g)
• Persistent hematuria
• Abnormal kidney biopsy findings
• Structural abnormalities on imaging

Then you have CKD Stage 2, which carries increased cardiovascular risk and requires monitoring and intervention. 1

When It Is NOT CKD

If you have eGFR 60-89 mL/min/1.73 m² WITHOUT any evidence of kidney damage markers, you do not have CKD. 2, 1 This range may represent:

• Normal kidney function for your age
• Normal physiological variation
• Adequate kidney function requiring no specific intervention

Common Pitfalls to Avoid

Relying solely on serum creatinine or eGFR without assessing for albuminuria and other kidney damage markers leads to both overdiagnosis and underdiagnosis of CKD. 1, 3 The National Kidney Foundation emphasizes that:

• eGFR and UACR provide independent prognostic information 3
• Both must be measured to properly classify CKD risk 3
• Skipping albuminuria testing is a critical error in CKD evaluation 3

The presence of even mild albuminuria (UACR 30-300 mg/g) with eGFR 60-89 mL/min/1.73 m² significantly increases risk of progression and cardiovascular events compared to eGFR in this range without albuminuria. 5