Cystatin C Assay
Reagent | Cystatin C
An Indispensable Marker of Renal Impairment
Benefits of the Randox Cystatin C Assay
A correlation coefficient of r=1.00 was displayed when the Randox methodology was compared against commercially available methods.
The Randox cystatin C assay displayed a within run precision of < 4.2%.
Wide measuring range
The Randox cystatin C assay has a measuring range 0.4 – 10mg/l for the comfortable detection of clinically important results.
Stable to expiry date
The Randox cystatin C assay is stable to expiry date when stored at +2oC to +8oC.
Dedicated cystatin C calibrator and controls
Dedicated cystatin C calibrator and controls available offering a complete testing package.
Applications available detailing instrument-specific settings for the convenient use of the Randox cystatin C assay on a variety of clinical chemistry analysers.
Serum creatinine (SCr) is the most commonly utilised screening test for renal impairment; however, SCr can be affected by age, dietary protein intake, ethnicity, gender, and lean muscle mass. Consequently, the sensitivity of SCr for the early detection of kidney disease is poor and not suitable for the renal assessment in the elderly 1.
The biggest drawback of SCr is that up to 50% of renal function can be lost before significant SCr levels become detectable as SCr is insensitive to small changes in GFR. Consequently, treatment is not provided at the appropriate time which can be fatal, and so an earlier and more sensitive biomarker for renal function is imperative 2.
Cystatin C (CysC) is a low-molecular-weight (13.3kDa) non-glycosylated protein belonging to the cystatin protease inhibitor family 2, 3. Formed at a constant rate by all nucleated cells, CysC is freely filtered by the glomerular membrane in the kidneys, reabsorbed and fully catabolised by the proximal renal tubule and is not returned to the bloodstream, and so is the ideal marker of glomerular filtration rate (GFR) 3, 4.
Serum CysC levels are inversely correlated with GFR 3. The main advantage of CysC as a marker of renal function is in the creatinine ‘blind’ area, the elderly and in paediatrics 5. It has been reported that CysC has important associations with mortality across the GFR range, including those who are grouped as ‘preclinical kidney disease’ (GFR between 60 and 90mL/min per 1.73m2). Moreover, CysC has been identified as a stronger predictor of adverse cardiovascular outcomes compared to SCr. Combining SCr, CysC and urine albumin to SCr ratio improves risk stratification for kidney disease progression and mortality 6.
Acute kidney injury (AKI) presents with elevated levels of CysC in those with severe COVID-19 in comparison to those with mild COVID-19. CysC can be utilised to determine the extent of kidney damage as well as distinguishing those with severe and mild COVID-19 7.
Cystatin C Calibrator
Cystatin C Control
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The month of January has forever been the month of resolutions with many choosing to ditch the sweets and join the gym. However, for many these efforts are limited to January and bad habits are quick to remerge. Obesity has been a burden on the health service for many years with the problem, like many people’s waist lines, only continuing to expand.
Recent findings have shown that this problem is no longer just increasing in developed countries but also in developing countries. In fact, worldwide obesity has tripled since 1975. In 2016, more than 1.9 million adults were classed as overweight, of which over 650 million were obese.1 These are shocking statistics for a condition that is preventable. As a global concern, it is important to assess all the potential risks of this problem.
The most common diseases associated with obesity are cardiovascular disease (CVD) and diabetes. However, the associated risks are much greater than this. Being overweight may also increase the risk of certain types of cancer, sleep apnea, osteoarthritis, fatty liver disease and kidney disease.2
Obesity is now recognised as a potent risk factor for the development of renal disease.3 Excess weight has a direct impact on the development and progression of chronic kidney disease (CKD). Globally, the prevalence of diabetic kidney disease rose by 39.5% between 2005 and 2015, coinciding with the increased CKD prevalence.4 In obese individuals, the kidneys have to work harder, filtering more blood than normal to meet the metabolic demands of increased body weight, increasing the risk of kidney disease.
The traditional diagnostic test for renal impairment is creatinine. This test is carried out through the measurement of creatinine levels in the blood to assess the kidneys ability to clear creatinine from the body. This is called the creatinine clearance rate which helps to estimate the glomerular filtration rate (GFR), which is the rate of blood flow through the kidneys.5
Problems arise when using creatinine for CKD testing as a number of factors need to be taken into consideration including age, gender, ethnicity and muscle mass. For this reason, black men and women exhibit higher creatinine levels than white men and women, raising concern over the accuracy of this test for certain patient groups.6 In addition, serum creatinine is not an adequate screening test for renal impairment in the elderly due to their decreased muscle mass.7
The main disadvantage of using creatinine to screen for renal impairment is that up to 50% of renal function can be lost before significant creatinine levels become detectable as creatinine is insensitive to small changes in GFR. Consequently, treatment is not provided at the appropriate time which can be fatal, therefore, an earlier and more sensitive marker for renal function is vital.8
These disadvantages have not only been highlighted in research but also by the national institute for health and care excellence (NICE). NICE updated the classification of CKD in 2004 to include the albumin: creatinine ratio (ACR). They split chronic kidney disease patients into categories based on GFR and ACR. Figure 1 highlights the different categories and risk of adverse outcomes. NICE recommend using eGFR Cystatin C for people in the CKD G3aA1 and higher.9
Figure 1 Classification of Chronic Kidney Disease using GFR and ACR categories.9
Despite these suggestions, Creatinine is still being used for G3a1 and increasing risk levels.
The utility of cystatin C as a diagnostic biomarker for kidney disease has been documented to show superiority of traditional CKD tests. There is no ‘blind area’ making it very sensitive to small changes in GFR and capable of detecting early reductions. Furthermore, this marker is less influenced by diet or muscle mass and has proven to be a beneficial test in patients who are overweight.8
A number of studies support the statement: ‘Cystatin C levels are higher in overweight and obese patients’. This is important because when cystatin c levels are too high, it may suggest that the kidneys are not functioning properly. One study conducted, using a nationally representative sample of participants, found that overweight and obesity maintained a strong association with elevated serum cystatin C. This suggests that weight can affect the levels of cystatin C and therefore the likelihood of developing kidney disease.10
How Randox can Help
The Randox automated Latex Enhanced Immunoturbidimetric Cystatin C tests offers an improved method for assessing CKD risk, combined with a convenient format for routine clinical use, for the early assessment of at risk patients. Randox is currently one of the only diagnostic manufacturers who offer an automated biochemistry test for Cystatin C measurement, worldwide.
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- World Health Organization. Obesity and Overweight . int. [Online] WHO. [Cited: January 22, 2019.] https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight.
- Health Risks of Being Overweight. NIDDK. [Online] National Institute of Diabetes and Digestive and Kidney Diseases. [Cited: March 24, 2019.] https://www.niddk.nih.gov/health-information/weight-management/health-risks-overweight.
- Kidney Health Australia . Obesity and Chronic Kidney Disease: The Hidden Impact. Kidney Health Week/ World Kidney Day 2017. [Online] Kidney Health Australia. [Cited: January 22, 2019.] https://kidney.org.au/cms_uploads/docs/kidney-health-australia-report-obesity-and-chronic-kidney-disease–the-hidden-impact_06.03.17.pdf.
- Neuen, Brendon Lange, et al. Chronic kidney disease and the global NCDs agenda. s.l. : BMJ Global Health, 2017
- Creatinine and Creatinine Clearance Blood Tests. WebMD. [Online] WebMD. [Cited: January 22, 2019.] https://www.webmd.com/a-to-z-guides/creatinine-and-creatinine-clearance-blood-tests#1.
- Lascano, Martin E and Poggio, Emilio D. Kidney Function Assessment by Creatinine-Based Estimation Equations. Cleveland Clinic. [Online] August 2010. [Cited: 16 May 2018.] http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/nephrology/kidneyfunction/.
- Swedko, Peter J, et al. Serum Creatinine Is an Inadequate Screening Test for Renal Failure in Elderly Patients. Research Gate. [Online] February 2003. [Cited: 6 May 2018.] https://www.researchgate.net/publication/8243393_Serum_Creatinine_Is_an_Inadequate_ Screening_Test_for_Renal_Failure_in_Elderly_Patients.
- Mishra, Umashankar. New technique developed to detect chronic kidney disease. Business Line. [Online] 07 May 2018. [Cited: 17 May 2018.] https://www.thehindubusinessline.com/news/science/new-technique-to-detect-chronic-kidney-disease/article23803316.ece.
- National Institute for Health and Care Excellence. Chronic kidney disease in adults: assessment and management: 1 Recommendations. National Institute for Health and Care Excellence. [Online] January 2015. https://www.nice.org.uk/guidance/cg182/chapter/1- recommendations#classification-of-chronic-kidney-disease-2.
- Overweight and Obesity and Elevated Serum Cystatin C Levels in US Adults . Muntner, Paul, et al. 4, s.l. : NCBI, 2008, Vol. 121.