Beyond Creatinine: Integrating Cystatin C into Clinical Practice

Kidney function in clinical practice is currently estimated using serum creatinine; although it is known to be an imperfect marker, as it is influenced by many factors that are independent of glomerular filtration rate (GFR), such as age, sex, diet, muscle mass, etc.  

Over the past decade, cystatin C has emerged as an alternative marker of kidney function and GFR. It is a low molecular weight protein that is secreted by all the nucleated cells in the body. Cystatin C is not as influenced by muscle mass as serum creatinine. Cystatin C has also been shown to be a better marker of kidney function and a better predictor of end stage kidney disease.  

Reflecting the growing body of evidence supporting the clinical utility of cystatin C, the most recent KDIGO guidelines recommend measuring serum cystatin C in patients with chronic kidney disease to confirm the diagnosis and improve prognostic assessment. 

Cystatin C also has important implications for medication dosing. Cystatin C based estimates of GFR may help refine dosing of renally cleared medications and reduce the risk of under- or overdosing in clinical practice. 

In this webinar Dr. Potok will review the biological basis of cystatin C, identify patient populations most likely to benefit from testing, and provide guidance on interpreting results, especially when creatinine and cystatin C based eGFR differ. Current barriers to cystatin C testing and implementation in routine clinical practice will be discussed. In addition, the role of cystatin C in medication dosing will also be addressed.

Learning Objectives:

• Understand cystatin C is and how it is used

• Identify who will benefit from a cystatin C test

• How to interpret test results, especially when eGFRcr and eGFRcys differ

• Combine eGFRcr and eGFRcys to improve drug dosing

• Current barriers to cystatin C testing and implementation in clinical practice