Is a patient with a history of chronic kidney disease (CKD) always in stage 3a if their Glomerular Filtration Rate (GFR) improves above 60 ml/min/1.73m^2?

No, You Are Not Always in Stage 3a CKD if Your GFR Improves Above 60

If your GFR improves above 60 mL/min/1.73 m² and remains there for more than 3 months, you no longer meet the criteria for Stage 3a CKD, provided you have no other markers of kidney damage. 1

Understanding the Core Definition of CKD

The fundamental definition of CKD requires either kidney damage or a GFR less than 60 mL/min/1.73 m² persisting for 3 months or longer. 1 This is a critical distinction that many clinicians misunderstand.

When GFR Alone Defines CKD

• A GFR below 60 mL/min/1.73 m² by itself is sufficient to diagnose CKD when it persists for more than 3 months, regardless of whether other markers of kidney damage are present. 1, 2
• A GFR above 60 mL/min/1.73 m² requires additional evidence of kidney damage to diagnose CKD, such as albuminuria (≥30 mg/g), abnormal kidney imaging, or history of kidney transplantation. 1, 2

The 3-Month Rule is Essential

• Any improvement in GFR must be sustained for at least 3 months before you can definitively say the patient no longer has Stage 3a CKD. 1, 3
• A single measurement showing GFR >60 does not immediately remove the CKD diagnosis—confirmation with repeat testing is required. 3

The Reality of CKD Stage Variability

CKD Stages Fluctuate More Than You Think

Research demonstrates that CKD stages changed in 40% of elderly patients when measured 5 times over just 1 year, with 17.2% showing fluctuating patterns. 4 This means:

• 60.4% had static CKD stages (remained in the same category throughout). 4
• 7.4% showed improving CKD stages (moved to better kidney function categories). 4
• 14.4% showed worsening stages. 4
• 17.2% fluctuated between different stages. 4

Clinical Implications of Improvement

When patients demonstrate improving CKD stage patterns, they have a significantly lower risk of subsequently requiring dialysis compared to those with static or worsening stages. 4 This validates that improvement is real and clinically meaningful, not just laboratory noise.

Common Pitfalls in GFR Interpretation

The Accuracy Problem at Higher GFR Values

Clinical laboratories do not report GFR estimates greater than 60 mL/min/1.73 m² as numeric values because estimating equations have reduced accuracy at higher GFR levels. 1 Instead, they report ">60 mL/min/1.73 m²". 5 This creates challenges:

• It may be difficult to interpret GFR estimates just below 60 mL/min/1.73 m² in some patients, particularly those without other markers of kidney damage. 1
• 23% of kidney transplant recipients with creatinine-based eGFR between 45-60 were incorrectly classified as having CKD when their measured GFR was actually above 60. 1

When to Use Cystatin C for Confirmation

KDIGO guidelines recommend measuring cystatin C in adults with creatinine-based eGFR 45-59 mL/min/1.73 m² who lack markers of kidney damage to confirm whether CKD truly exists. 1, 6, 7

• If the combined creatinine-cystatin C equation (eGFRcreat-cys) is also <60, CKD is confirmed. 1, 7
• If eGFRcreat-cys is >60, the diagnosis of CKD is not confirmed, and the patient should not be labeled as having Stage 3a disease. 1, 7

The Correct Clinical Algorithm

Step 1: Confirm the Improvement is Real

• Repeat GFR measurement after at least 3 months to ensure the improvement is sustained. 1, 3
• If the patient has borderline values (just above 60), consider cystatin C testing to confirm true kidney function. 1, 6, 7

Step 2: Assess for Other Markers of Kidney Damage

• Check for albuminuria (urine albumin-to-creatinine ratio). 1, 2
• Review for abnormal kidney imaging findings. 1
• Document any history of kidney transplantation. 1

Step 3: Make the Diagnosis

• If GFR >60 for >3 months AND no markers of kidney damage exist: The patient does NOT have CKD. 1, 2
• If GFR >60 but markers of kidney damage persist: The patient has CKD Stage 1 or 2 (depending on exact GFR level). 1, 2
• If GFR remains <60 for >3 months: The patient continues to have Stage 3 CKD regardless of other factors. 1

Important Caveats

The Misdiagnosis Problem

Assigning a diagnosis of CKD to a patient with normal renal function and absence of other evidence of kidney damage may have negative consequences, including insurance issues and unnecessary medical interventions. 2 This underscores the importance of correctly applying the diagnostic criteria.

Age and Population Considerations

The CKD-EPI equation leads to higher GFR estimates in younger people and lower estimates in the elderly, which can affect stage classification. 8 In elderly patients, what appears as Stage 3a by creatinine-based eGFR may actually represent normal age-related kidney function decline rather than disease. 8

Stage 3a vs 3b Distinction Matters

If a patient does remain in Stage 3, distinguishing between Stage 3a (GFR 45-59) and Stage 3b (GFR 30-44) is clinically important because Stage 3b patients have significantly higher risks of progression to kidney failure and cardiovascular events. 9 About half of Stage 3 CKD patients progressed to Stage 4 or 5 over 10 years, with Stage 3b patients at nearly 3-fold higher risk (HR 2.99) than Stage 3a patients. 9