From the Guidelines
Cystatin C is a reliable marker for kidney function and should be used alongside or as an alternative to creatinine-based measurements, especially in populations where creatinine-based estimates may be misleading, such as the elderly or those with reduced muscle mass. This is because cystatin C levels are not significantly affected by muscle mass, age, gender, or diet, providing a more accurate assessment of kidney function 1. Cystatin C testing is particularly useful when creatinine-based estimates of GFR may be misleading, and normal cystatin C levels typically range from 0.5 to 1.0 mg/L, with higher values indicating decreased kidney function.
Key Points
- Cystatin C is a small protein produced by all nucleated cells in the body that serves as a reliable marker for kidney function 1
- Cystatin C levels are not significantly affected by muscle mass, age, gender, or diet, providing a more accurate assessment of kidney function in certain populations such as the elderly, those with reduced muscle mass, children, or individuals with liver disease 1
- Cystatin C-based GFR equations often provide better risk prediction for kidney disease progression and cardiovascular outcomes compared to creatinine-based equations alone 1
- Cystatin C testing is particularly useful when creatinine-based estimates of GFR may be misleading, and normal cystatin C levels typically range from 0.5 to 1.0 mg/L, with higher values indicating decreased kidney function
Clinical Utility
The use of cystatin C as a marker for kidney function has important implications for clinical practice, particularly in the management of patients with kidney disease or those at risk of developing kidney disease. By providing a more accurate assessment of kidney function, cystatin C can help guide medication dosing, disease monitoring, and early detection of kidney dysfunction. Additionally, cystatin C-based GFR equations can provide better risk prediction for kidney disease progression and cardiovascular outcomes, allowing for more targeted and effective treatment strategies.
Recommendations
The use of cystatin C as a marker for kidney function is recommended, particularly in populations where creatinine-based estimates may be misleading. This includes the elderly, those with reduced muscle mass, children, or individuals with liver disease. Cystatin C testing should be used alongside or as an alternative to creatinine-based measurements, especially when more precise evaluation of kidney function is needed for medication dosing, disease monitoring, or early detection of kidney dysfunction.
From the Research
Cystatin C as a Biomarker
- Cystatin C is a reliable and accurate marker of kidney function across diverse populations 2
- It has been well established as an early and accurate biomarker of chronic kidney disease (CKD) 3
- Serum cystatin C levels are less influenced by factors other than glomerular filtration rate (GFR) compared to creatinine 4, 5
Clinical Considerations
- The 2012 Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommended using cystatin C to confirm the diagnosis of CKD determined by creatinine-based estimated GFR 2
- Cystatin C is useful for risk stratification in heart failure and has been predictive of incident or recurrent cardiovascular events and adverse outcomes 4
- Routine screening and timely intervention are recommended to reduce the risk of cardiovascular diseases in CKD patients 6
Advantages and Limitations
- Cystatin C correlates with true GFR more accurately than creatinine 4
- Equations for estimating GFR from cystatin C values have been developed, making values easier to interpret and facilitating clinical use 4
- However, transition of all reagents and estimated GFR equations to the newly established International Standard is critical for developing generalizable data 3