Use of Cystatin C to Assess Kidney Function

Mayo Renal Laboratory Cystatin C By Particle Enhanced Turbidometric Immunoassay (PETIA)

August 2011

The Mayo Clinic renal laboratory has recently evaluated a new cystatin C assay.  It is a particle-enhanced turbidometric immunoassay, or PETIA, and can be run on a chemistry autoanalyzer. This confers certain lab advantages including high-capacity, quick turnaround time, and lower-cost compared to other platforms. Importantly, this assay is also standardized to a cystatin C international reference material. Our validation studies revealed very low within and between run coefficient of variations of 0.65-1.33%. The lower limit of quantification was 0.35 mg per liter, with an upper range of 6 mg per liter.

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Jump to section:

• Introduction
• A Case
• Questions
• What do the kidneys do?
• Why Measure Renal Function?
• How Is Chronic Kidney Disease (CKD) Defined?
• Stages of Chronic Kidney Disease
• Laboratory Assessment of Kidney Function: What Can We Measure?
• Creatinine as a Marker of GFR
• Creatinine as a Marker of GFR: It Works But...
• How Can We Turn the Serum Creatinine Into a Better Estimate of GFR?
• Revised eGFR Equation (ID-MS version)
• eGFR Equation Works, But it's Not Perfect
• What About Cystatin C?
• Mayo Renal Laboratory Cystatin C By Particle Enhanced Turbidometric Immunoassay (PETIA)
• Comparison To Current Nephelometric Assay (PENIA) Reveals 23% Bias
• Cystatin C PENIA Assay Shift (19%)
• Cystatin C eGFR Using Published Equation* Performs Well³
• Cystatin C Equations Categorize Patients Slightly Better Than MDRD eGFR
• Cystatin C Reference Range
• PETIA Cystatin C Reference Range
• Cystatin C: Useful To Confirm Those At Risk Of CKD Progression And Its Complications (REGARDS)⁴
• Cystatin C: CKD Progression and Complications (MESA and CHS)⁵
• Cystatin C in the Acute Hospitalized Setting⁶
• Back to Our Patient
• Potential Interventions
• Conclusions
• References
• Questions?