Does a GFR of 64 ml/min/1.73m² Confirm CKD Stage 3a?
No, a single GFR measurement of 64 ml/min/1.73m² does NOT confirm CKD stage 3a, because this value falls above the 60 ml/min/1.73m² threshold that defines stage 3a CKD. 1
Understanding CKD Stage 3a Definition
CKD stage 3a is defined as a GFR between 45-59 ml/min/1.73m², not 60-89 ml/min/1.73m² 1. Your measurement of 64 ml/min/1.73m² places you in the stage 2 CKD range (60-89 ml/min/1.73m²), which requires evidence of kidney damage (such as albuminuria, hematuria, or anatomical abnormality) to even be classified as CKD 1, 2.
Critical Diagnostic Requirements
To diagnose CKD at any stage, you need both of the following 1, 2:
- Temporal component: Abnormalities must be present on at least two occasions over three months or longer
- Either: Evidence of kidney damage (proteinuria, albuminuria, hematuria, or anatomical abnormality) OR GFR <60 ml/min/1.73m²
Since your GFR is 64 ml/min/1.73m², you would need documented markers of kidney damage to be diagnosed with CKD stage 2 1.
Important Caveats About GFR Measurement
The method used to estimate GFR matters significantly. If your 64 ml/min/1.73m² was calculated using a creatinine-based equation (eGFRcreat), this may not accurately reflect your true kidney function, particularly if you have 1, 3, 4:
- Variable muscle mass
- Malnutrition or extreme body composition
- Advanced age
- Extreme exercise patterns
KDIGO guidelines recommend measuring cystatin C in adults with eGFRcreat 45-59 ml/min/1.73m² who lack other markers of kidney damage to confirm whether CKD truly exists 1, 3. While your value of 64 ml/min/1.73m² falls outside this specific recommendation range, if you have conditions affecting muscle mass, cystatin C testing could provide more accurate assessment 4.
Healthy Adult Reference Values
Research demonstrates that healthy adults can have eGFR values as low as 63.5 ml/min/1.73m² using the MDRD equation 5. This means an eGFR greater than 60 ml/min/1.73m² does not exclude kidney disease, but it also means values in the low 60s can be entirely normal 5.
Clinical Bottom Line
Your GFR of 64 ml/min/1.73m² is:
- Above the threshold for stage 3a CKD (which requires GFR 45-59 ml/min/1.73m²) 1
- Within the stage 2 range (60-89 ml/min/1.73m²), which requires additional evidence of kidney damage to diagnose CKD 1
- Potentially within normal range for healthy adults, depending on the equation used 5
To establish any CKD diagnosis, you need repeat measurements over at least 3 months showing persistent abnormalities 1, 2. A single measurement of 64 ml/min/1.73m² confirms nothing definitive about CKD status.