Cystatin C — Renal Function Marker¶
1. What is Cystatin C?¶
Cystatin C is a low-molecular-weight protein produced at a constant rate by all nucleated cells and cleared almost exclusively by glomerular filtration. Like SDMA, it is less affected by muscle mass than creatinine, making it a useful complementary marker for estimating glomerular filtration rate (GFR).
2. Data Card¶
| Field | Value |
|---|---|
| Biomarker | Cystatin C (CysC) |
| Full name | Cystatin C |
| Organ | Kidney (renal function / GFR) |
| Species | Canine, Feline |
| Specimen | Serum / Plasma |
| Method | FICT (Fluorescence Immunochromatography) |
| Analyzer | FIA680 / FIA880 |
| Unit | mg/L |
3. Reference Range¶
| Species | Reference Range | Elevated Indicates |
|---|---|---|
| Canine | 0.1–0.5 mg/L (typical) | > 0.5 mg/L — reduced GFR |
| Feline | 0.1–0.4 mg/L (typical) | > 0.4 mg/L — reduced GFR |
Reference ranges vary by laboratory and method. Confirm against your local reference population and the product IFU.
4. Clinical Significance¶
- GFR estimation: Cystatin C rises as GFR declines, and — like SDMA — is less dependent on muscle mass than creatinine.
- Early detection: Detects renal impairment earlier than creatinine alone in many patients.
- Complementary marker: Used alongside creatinine and SDMA to strengthen the assessment of renal function.
5. Cystatin C vs Creatinine vs SDMA¶
| Attribute | Cystatin C | Creatinine | SDMA |
|---|---|---|---|
| Affected by muscle mass | Minimally | Yes | No |
| Early GFR loss detection | Earlier than creatinine | Late (~75% loss) | Early (~40% loss) |
| Affected by diet | Minimal | Mildly | No |
| Established staging system | No (adjunct) | Yes (IRIS) | Yes (IRIS) |
| Role | Complementary GFR marker | Traditional GFR marker | Early CKD marker |
6. Analytical Performance (Migibio Assay)¶
| Metric | Value |
|---|---|
| LOD | 0.02 mg/L |
| LOQ | 0.05 mg/L |
| Linear range | 0.05–10 mg/L |
| Intra-assay CV% | < 8% |
| Inter-assay CV% | < 10% |
| Correlation vs reference (r) | > 0.95 |
7. Interpretation Guide¶
| Cystatin C (mg/L) | Interpretation |
|---|---|
| Within reference range | Normal renal function |
| Mildly elevated | Reduced GFR — correlate with creatinine/SDMA |
| Markedly elevated | Significant renal impairment — pursue IRIS staging |
For clinical application, see the knowledge base. For validation methodology, see the research center.
Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.