Kidney Function: Cystatin C vs. Creatinine in Determining Risk

[CoastWatcher]

Does adding the measurement of cystatin C to that of serum creatinine to determine estimated glomerular filtration rate improve its accuracy? That's the question asked by researchers who undertook a meta-analysis of 11 general population studies (90,750 participants) and five studies of cohorts with chronic kidney disease (2,960 participants) for whom standardized measurements of serum creatinine and cystatin C were available.

• Researchers compared the association of the eGFR as calculated by the measurement of creatinine or cystatin C alone or in combination with creatinine, with the overall rate of death, death from cardiovascular causes, and end-stage renal disease.
• Across all eGFR categories, the reclassification of the eGFR to a higher value with the measurement of cystatin C, as opposed to creatinine, was associated with a reduced risk of all three study outcomes; reclassification to a lower eGFR was associated with an increased risk.

The use of cystatin C - alone or in combination with creatinine - strengthens the association between eGFR and the risks of death and end-stage renal disease across diverse populations.


The New England Journal of Medicine, 5 September 2013

http://www.nejm.org/doi/full/10.1056/NEJMoa1214234

 

[Re-Ride]

Thanks C.W., good to know. Makes me wonder why doctors at leading kidney clinics don't run this test, Stanford or UCSF for example. It's not available from Discounted labs and may oir may not be covered by Medicare. National Kidney foundation suggests that the cystatin c test may be a helpful dianostic for CKD for those who are overweight, muscular or elderly.
https://www.kidney.org/atoz/content/cystatinC

The standard of kidney care today is wait for blood or protein in the urine then slam you with dye + CAT scan which of course diagnoses nothing so its on to highly toxic gadnolinium dye + MRI which they want to repeat regularly until you finally do develop kidney tumors. Ahh! Goal achieved! Another pt under the knife for surgical excision of the kidney they killed in the first place either with the diagnostics or with earlier regimens of nephrotoxic maintenance drugs. Better one should educate himself early on about the many environmental exposures that lead to nephrotoxicity and to understand the risks posed by OTC drugs as well as ANY big pharma drug prescribed for you. Must know possible drug interactions too. Unless you are fairly certain that you have a fracture that can benefit from orthopedic remediation just say NO to routine X-rays of the thorax and head. Like the kind they are so quick to order after every minor accident. This especially includes the pelvic dexiscan bone density scam.

 

[Nelson Vergel]

I am making it available soon on DiscountedLabs.com

Negotiating a good price now.

 

[Nelson Vergel]

"The downsides of using GFRs, he added, include the fact that they are mostly validated in younger patients with kidney disease, they rely on the assumption that demographic characteristics alone can define muscle mass, they were only developed in whites and blacks, and estimated GFR can be interpreted only as “suggested GFR.”

A blood test of kidney function known as cystatin C has been shown to be an alternative, better marker of creatinine, compared with GFR, and is supported by the Kidney Disease: Improving Global Outcomes CKD work group's 2012 clinical practice guidelines for the evaluation and management of CKD. “Because cystatin C is not related to muscle mass, age, sex, and race, it has major advantages over creatinine,” Dr. Shlipak said. “It is a reliable, standardized, and automated measure that is available for clinical use.”

Obtaining cystatin-C levels useful in chronic kidney disease

 

[Nelson Vergel]

Creatinine: An Inaccurate Measure of Renal Function in Men with Testosterone-Induced Muscle Hypertrophy​

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K Campbell, B Brunner, J Sullivan, O Velazquez… - The Journal of Sexual …, 2022

| VOLUME 19, ISSUE 4, SUPPLEMENT 1, S5-S6, APRIL 01, 2022​

Introduction​

Renal function is often estimated using validated study equations and serum creatinine (Cr) as a filtration marker. Contemporary studies suggest that cystatin C may be used as a more accurate alternative to Cr, as it avoids limitations related to diet and muscle mass that affect Cr and predispose to an overdiagnosis of chronic kidney disease. Elite athletes are often noted to have an elevated body mass index (BMI) despite maintaining an overall favorable level of percent body fat (PBF) and fitness. This is due to an increase level of body muscle.

Objective​

This study evaluates the relationship between Cr, cystatin C, BMI, and PBF in fitness and elite athlete populations.

Methods​

Elite athletes presenting to a men's health tertiary referral center with muscle-induced hypertrophy were evaluated for renal function through serum levels of Cr and cystatin C. BMI and PBF were obtained through bioimpedance testing at the time of serum level determinations. Elite athletes were those identified as pursuing competition in professional or amateur sporting events. Cr and cystatin c were plotted for correlation in best fit models for percentage increments of BMI (“normal”, “overweight”, and “obese”) and PBF.

Results​

A total of 228 elite athletes were identified and stratified by BMI and PBF (Figures 1,2). The majority of athletes were classified as “overweight” (n = 88) or “obese” (n = 129) per BMI. None of the BMI groups demonstrated a significant correlation between Cr and cystatin C levels (Figure 1). The obese cohort demonstrated increased levels of cystatin C (mean = 1.00337, P<0.0001) compared with the overweight cohort (mean = 1.474462, p P<0.0001). The majority of athletes maintained a PBF of 10-20% (n = 87). PBF did not demonstrate a significant correlation between Cr and cystatin C levels, with the PBF 20-30% cohort approaching moderate correlation (R2 = 0.49, p =<0.0001).

Conclusions​

Our study affirms that elite athletes maintain an increased BMI and low PBF. Hence, cystatin C may demonstrate a more accurate reflection of renal function in these patients, as Cr may be inaccurately elevated.

Disclosure​

Any of the authors act as a consultant, employee or shareholder of an industry for: Abbie, American Medical Systems, Augmenta LLC, Clarus Therapeutics, Endo Pharmaceuticals, Lipocine, Vault Health