CKD Diagnosis Clarification: eGFR Thresholds and Reversibility
You Are Correct About the Stage 3a Threshold
You are absolutely correct that an eGFR of 64 mL/min/1.73 m² does not meet the diagnostic threshold for Stage 3a CKD, which requires eGFR below 60 mL/min/1.73 m². 1 The combined equation result of 64 mL/min/1.73 m² actually confirms that you do NOT have CKD based on eGFR criteria alone, assuming no other markers of kidney damage are present. 1
Understanding the CKD Diagnostic Framework
The diagnosis of CKD requires one of two conditions to be met for at least 3 months: 1
- eGFR <60 mL/min/1.73 m² (sufficient alone, no additional markers needed)
- eGFR 60-89 mL/min/1.73 m² PLUS documented kidney damage (albuminuria, pathological abnormalities on biopsy, urine abnormalities, or history of kidney transplantation) 1
Since your combined eGFR is 64 mL/min/1.73 m², you would only have CKD if you also have documented kidney damage markers present for ≥3 months. 1
The KDIGO Confirmation Strategy Explained
The KDIGO guidelines recommend measuring cystatin C specifically for patients with creatinine-based eGFR of 45-59 mL/min/1.73 m² who lack other markers of kidney damage. 2, 3 The confirmation algorithm works as follows:
- If the combined equation (eGFRcreat-cys) is <60 mL/min/1.73 m²: CKD diagnosis is confirmed 2, 3
- If the combined equation (eGFRcreat-cys) is ≥60 mL/min/1.73 m²: CKD diagnosis is NOT confirmed 2, 3
This strategy exists because approximately 23% of patients with creatinine-based eGFR in the 45-59 range actually have normal kidney function when confirmed with cystatin C. 1, 3
Does Temporary Stage 3a Mean Lifelong CKD?
No, a patient who temporarily had eGFR <60 mL/min/1.73 m² but subsequently maintains eGFR ≥60 mL/min/1.73 m² permanently does NOT have CKD for life, assuming no kidney damage markers persist. 1
The critical element is the 3-month duration requirement. CKD requires either: 1
- Reduced eGFR (<60 mL/min/1.73 m²) persisting for ≥3 months, OR
- Evidence of kidney damage persisting for ≥3 months
If kidney function improves and remains above 60 mL/min/1.73 m² permanently, and no kidney damage markers are present, the patient no longer meets diagnostic criteria for CKD. 1 This is particularly relevant because research shows that eGFR values in healthy adults can range as low as 63.5 mL/min/1.73 m², and these normal values overlap with CKD stages 1 and 2. 4
Important Caveats About eGFR Interpretation
The combined creatinine-cystatin C equation provides 94.9% accuracy within 30% of measured GFR and should be the definitive value used for clinical decision-making when discordance exists between creatinine-based and cystatin C-based estimates. 5 In your case, with a combined eGFR of 64 mL/min/1.73 m², this represents the most accurate assessment of your kidney function. 5
Normal GFR values are approximately 130 mL/min/1.73 m² for men and 120 mL/min/1.73 m² for women, with a mean decline of 0.75 mL/min/year with aging. 2 An eGFR >60 mL/min/1.73 m² does not exclude kidney disease if damage markers are present, but in the absence of such markers, it indicates you do not have CKD. 4