An estimate of kidney filtration based on cystatin C, independent of muscle mass.
eGFR (cystatin C) is an estimate of how well your kidneys filter blood, calculated from the level of cystatin C. Cystatin C is a protein made by all cells at a steady rate and cleared by the kidneys, so its blood level reflects filtration.
The result is a calculated value using a validated equation, usually CKD-EPI, and is reported in mL/min per 1.73 square metres of body surface area.
eGFR is the standard way to gauge overall kidney function. The cystatin C version is useful because, unlike creatinine, it is not strongly affected by muscle mass, so it can be more accurate in people who are very muscular, frail, or elderly.
A lower eGFR means slower filtration and reduced kidney function. It is used to stage chronic kidney disease and to track changes over time.
Aniva reads your result against research-backed ranges, not just the lab's wide normal. The reference shown below is specific to this biomarker.
eGFR is staged rather than given as a single normal range:
| Stage | eGFR (mL/min/1.73m²) |
|---|---|
| Normal or high (G1) | 90 or above |
| Mildly reduced (G2) | 60 to 89 |
| Moderately reduced (G3) | 30 to 59 |
| Severely reduced (G4) | 15 to 29 |
| Kidney failure (G5) | below 15 |
Staging follows KDIGO. A single mildly reduced value is common and often not concerning on its own.
Thyroid disease, steroid use, and marked inflammation can affect cystatin C and therefore the estimate. The equation assumes a steady state, so it is less reliable when kidney function is changing quickly. It is an estimate, not a direct measurement.
Read alongside cystatin C itself, creatinine-based eGFR, and urine albumin to creatinine ratio.
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