Cystatin C: A Reliable Marker

What is Cystatin C? 

Cystatin C

Cystatin C (CysC) is a crucial low molecular weight protein that is produced by all nucleated cells and is found in all biological fluids including plasma (serum), saliva, and urine. The Cystatin C is taken up by the proximal tubes and then metabolized so that it does not return into the bloodstream. As a result, serum Cystatin C closely correlates to glomerular filtration rate (GFR). The normal range of serum Cystatin C is around 0.62-1.15 mg/L (1). An abnormally high level of Cystatin C in your blood may point to renal dysfunction. In addition to renal dysfunction/disease, higher levels of Cystatin C can also point to diabetes, chronic inflammation, obesity, cancer, and hyperthyroidism (5,6).

 Cystatin C is a marker for GFR

Glomerular filtration rate (GFR) remains the ideal marker for kidney function & it is commonly assessed by measuring serum markers such as blood urea nitrogen & serum creatinine (4).

Cystatin C and glomerular filtration rateCystatin C is a newer biomarker for GFR & it is not dependent upon age, race, gender, and muscle mass- unlike Creatinine. This means that the serum concentration of Creatinine can still differ between individuals with the same kidney function. Creatinine levels typically do not rise until 50% of the kidney is not functioning properly which can lead to inaccurate test results. It is important to note that early diagnosis of renal dysfunction is imperative to survive. Cystatin C has been show to be a more reliable biomarker than Creatinine as an indicator of true GFR and to add information about the occurrence of acute kidney injury. However, the best GFR estimation requires both Cystatin C & Creatinine based equations. The conclusion is that Cystatin C should be used just as often (if not more) as Creatinine in clinical medicine & research.

      Our Cystatin C ELISAs (human, mouse, rat) can provide an avenue for assessing renal dysfunction especially following surgery. Together with Cystatin C, a GFR marker, urinary Cystatin C would be a biomarker of AKI and/or assessing response to therapeutic interventions in experimental and clinical research.

 Citations

1. Murty, M S N et al. “Serum cystatin C as a marker of renal function in detection of early acute kidney injury.” Indian journal of nephrology vol. 23,3 (2013): 180-3. doi:10.4103/0971-4065.111840

2. National Institute of Diabetes and Digestive and Kidney Diseases. Explaining Your Kidney Test Results: A Tool For Clinical Use. 2014, August.

3. Kar S, Paglialunga S, Islam R. Cystatin C Is a More Reliable Biomarker for Determining eGFR to Support Drug Development Studies. J Clin Pharmacol. 2018 Oct;58(10):1239-1247. doi: 10.1002/jcph.1132. Epub 2018 May 18. PMID: 29775220.

4. Omar F Laterza, Christopher P Price, Mitchell G Scott, Cystatin C: An Improved Estimator of Glomerular Filtration Rate?, Clinical Chemistry, Volume 48, Issue 5, 1 May 2002, Pages 699–707,

5. Muslimovic, Alma et al. “Serum cystatin C – marker of inflammation and cardiovascular morbidity in chronic kidney disease stages 1-4.” Materia socio-medica vol. 27,2 (2015): 75-8. doi:10.5455/msm.2015.27.75-78

6. Muntner, Paul et al. “Overweight, obesity, and elevated serum cystatin C levels in adults in the United States.” The American journal of medicine 121,4 (2008): 341-8. doi:10.1016/j.amjmed.2008.01.003

7. Grubb, Anders. “Cystatin C is Indispensable for Evaluation of Kidney Disease.” EJIFCC vol. 28,4 268-276. 19 Dec. 2017

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