Estimated glomerular filtration rate (eGFR) plays a crucial role in assessing kidney function and guiding clinical decisions, and is especially important in diagnosing chronic kidney disease (CKD).1 Today eGFR is most often calculated using the biomarker serum creatinine alone (CKD-EPI creatinine equation). Creatinine is a widely used and cost-effective biomarker, it can, in some cases, offer an incomplete assessment of kidney function.
Kidney health advocates and organisations suggest that combining two biomarkers - cystatin C and creatinine - can improve the accuracy and clinical utility of kidney function estimates.
So, are two biomarkers better than one?
Creatinine is a by-product of muscle metabolism2, and its levels in the blood can be influenced by several non-renal factors, including age, gender, ethnicity, muscle mass and diet (e.g., meat, creatine intake).3-7 These variables can lead to over- or underestimation of kidney function, particularly in populations such as:
Serum creatinine levels typically rise only after ~50% of renal function is lost, creating a “blind area” (30–70 mL/min/1.73 m²) where early CKD may go undetected.5 Relying on creatinine alone can delay diagnosis and timely intervention.
Cystatin C is a low-molecular-weight protein produced at a constant rate by all nucleated cells. It is freely filtered by the glomeruli and metabolised in the proximal tubules, with negligible reabsorption into the bloodstream.6,8 Unlike creatinine, cystatin C levels are largely unaffected by non-GFR factors such as muscle mass, sex, age, and dietary protein intake.3-5,9
This physiological stability makes cystatin C a more reliable indicator of kidney function, particularly in patients where creatinine-based estimates may be misleading. In the context of CKD, this improved precision is critical for detecting early-stage renal impairment and ensuring accurate staging. By enhancing diagnostic accuracy, cystatin C enables more informed clinical decisions, better risk stratification, and more personalised treatment strategies for patients with CKD.
However, it is important to acknowledge that cystatin C is not without limitations. Its levels may be influenced by factors such as corticosteroid use, hyperthyroidism, smoking, and obesity—considerations that clinicians should account for when interpreting results.
Using cystatin C alongside creatinine for eGFR assessment offers a more accurate and dependable evaluation of kidney function. Using both biomarkers in combination offers several clinical benefits:
Studies have shown that adding cystatin C can reclassify a significant portion of patients into more appropriate CKD stages, leading to better-informed clinical decisions.10
Leading international organisations have updated their recommendations adding cystatin C alongside creatinine:
The combination of cystatin C and creatinine represents a smarter, evidence-based approach to eGFR estimation. For healthcare providers looking to elevate kidney diagnostics, it's time to consider adding cystatin C to the equation.
The Gentian Cystatin C Immunoassay is a turbidimetric assay designed for use on most automated clinical chemistry analysers. As an open-channel assay, it can be easily integrated into a wide range of clinical chemistry platforms for flexible, high-throughput testing.
FDA 510(k) cleared since 2008
CE-marked and IVDR-certified (CE 0123)
Developed and manufactured in Norway
Utilises avian antibodies to reduce interference
Trusted globally and shipped from within the U.S, the Gentian Cystatin C Immunoassay offers a robust solution for enhancing kidney function diagnostics, supporting clinical decision-making with precision and consistency.
Interested in learning more about the Gentian Cystatin C Immunoassay or the clinical value of cystatin C in kidney diagnostics?
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