For many years, race was included in some kidney function calculations, especially estimated glomerular filtration rate, also known as eGFR. Today, kidney experts are moving away from race-based kidney function testing because race is not a reliable biological measure. Instead, newer approaches focus on more accurate markers, including creatinine, cystatin C, age, sex, and other clinical factors.
This shift matters because eGFR is one of the most important tools used to assess kidney function, classify chronic kidney disease, guide medication dosing, and determine when a person may need dialysis or a kidney transplant. When the calculation is inaccurate, it can delay care or create unequal outcomes. Recent NIDDK-supported research has helped push kidney medicine toward more equitable and accurate testing methods.
What Is eGFR?
Estimated glomerular filtration rate, or eGFR, is a lab-based estimate of how well the kidneys are filtering waste from the blood. The kidneys contain tiny filtering units called glomeruli. These filters help remove waste products, extra fluid, and toxins from the bloodstream.
A direct measurement of GFR can be done, but it is expensive, complicated, and not practical for routine care. Because of this, doctors usually estimate GFR using a blood test that measures creatinine.
Creatinine is a waste product created by normal muscle activity. The kidneys filter creatinine out of the blood, so when kidney function drops, creatinine levels often rise. This makes creatinine useful, but not perfect.
Creatinine levels can be affected by:
- Muscle mass
- Age
- Sex
- Diet, especially meat intake
- Certain medications
- Overall health status
This means two people with the same kidney function may not always have the same creatinine level.
Why Was Race Used in Kidney Function Calculations?
Race was previously included in some eGFR equations because research found that, on average, Black study participants had slightly higher creatinine levels than non-Black participants at the same measured GFR. Because of this, older equations sometimes adjusted the eGFR result upward for people identified as Black.
The problem is that race is a social category, not a precise biological measurement. It does not accurately reflect genetics, kidney function, muscle mass, or creatinine production in an individual person.
Research now shows that there is more genetic variation within racial groups than between racial groups. That means using race as a shortcut for biology can be misleading.
Why Race-Based Kidney Function Testing Is Problematic
Race-based kidney function testing can create real problems for patients. If an equation overestimates someone’s kidney function, their kidney disease may appear less severe than it actually is.
That can affect major medical decisions, including:
- When a person is referred to a kidney specialist
- When they qualify for transplant evaluation
- How medications are dosed
- How chronic kidney disease is staged
- How quickly doctors respond to declining kidney function
For example, if a Black patient’s eGFR is adjusted upward, it may look like their kidneys are working better than they really are. This could delay transplant eligibility or other needed care.
This is one reason many kidney organizations now support removing race from eGFR equations.
Race Does Not Accurately Measure Biology
One of the biggest issues with race-based kidney function testing is that race does not reliably predict individual biology. A person who identifies as Black may not have the higher creatinine-to-GFR pattern that older equations assumed.
At the same time, another person from a different background may have higher creatinine due to greater muscle mass, diet, or other factors.
Using race in a medical formula can lead to broad assumptions about people that do not apply to the individual patient. In kidney care, where small changes in eGFR can influence treatment decisions, this matters.
The Move Toward Race-Free eGFR
Newer kidney function equations are designed to estimate GFR without using race. These equations may still use creatinine, but they adjust for factors such as age and sex instead of racial category.
According to the research summarized by NIDDK, newer creatinine-based equations that do not include race may slightly underestimate eGFR in people who identify as Black and slightly overestimate it in some non-Black individuals. However, they remove the ethical and clinical problems caused by assigning biological meaning to race.
This is an important step toward fairer kidney disease diagnosis and monitoring.
What Is Cystatin C?
Cystatin C is another blood marker that can be used to estimate kidney function. It is a protein produced by cells in the body and filtered by the kidneys.
Unlike creatinine, cystatin C is less affected by muscle mass and does not vary based on race in the same way older creatinine assumptions suggested. Because of this, cystatin C may help provide a more accurate picture of kidney function.
Research has found that using both creatinine and cystatin C together can improve eGFR accuracy. This combined approach may be especially useful when a patient’s eGFR is close to an important medical decision point.
Why Creatinine and Cystatin C Together May Be Better
Using creatinine alone can be helpful, but it has limitations. Using cystatin C alone can also provide useful information. However, combining both markers may give doctors a clearer view of kidney function.
The creatinine-cystatin C equation may be especially important when decisions involve:
- Kidney transplant eligibility
- Medication dosing
- CKD staging
- Referral to a nephrologist
- Dialysis planning
- Monitoring changes in kidney function
When someone’s eGFR is near a cutoff point, even a small difference can affect care. In these cases, a more accurate estimate can help prevent delays or unnecessary treatment changes.
Why Cystatin C Is Not Used Everywhere Yet
Even though cystatin C can improve kidney function testing, it is not yet available everywhere as a routine test. Some laboratories do not offer it regularly, and insurance or reimbursement issues can make access harder.
Because of these barriers, many experts recommend using race-free creatinine-based equations now, while also expanding access to cystatin C testing.
The long-term goal is to make kidney function testing more accurate, practical, and fair for everyone.
What This Means for People With Kidney Disease
For people with chronic kidney disease, these changes are important. Kidney function numbers are not just numbers on a lab report. They can influence treatment, diet recommendations, medication safety, and long-term planning.
If you have kidney disease, it may be helpful to ask your healthcare provider:
- Which eGFR equation is being used?
- Is the lab using a race-free eGFR calculation?
- Would cystatin C testing be useful in your case?
- Is your eGFR close to a decision point for medication, referral, or transplant?
- Should your kidney function be monitored more closely?
This does not mean creatinine testing is useless. Creatinine is still widely used and helpful. But it does mean that kidney function should be interpreted carefully, especially when important medical decisions are being made.
Kidney Health and Equity
The removal of race from kidney function calculations is part of a larger effort to reduce health disparities in kidney disease. Chronic kidney disease affects millions of people, and unequal access to diagnosis, treatment, transplant evaluation, and specialty care can make outcomes worse.
Using more accurate and equitable testing methods is one way to improve care. It helps ensure that patients are evaluated based on their actual kidney function rather than a broad racial category.
This change also reflects a growing understanding in medicine: race should not be treated as a biological shortcut when better tools are available.
The Future of Kidney Function Testing
Kidney function testing will likely continue to evolve. Researchers are still looking for better ways to measure kidney health, predict disease progression, and personalize treatment.
Future approaches may include:
- Wider use of cystatin C
- Better biomarker combinations
- More individualized kidney risk assessment
- Improved lab access
- Better insurance coverage for advanced testing
- Continued research into kidney disease disparities
For now, the shift away from race-based kidney function testing represents an important improvement in how kidney disease is diagnosed and monitored.
Final Thoughts
Race-based kidney function calculations are being replaced because race is not a reliable biological measure. Older eGFR equations sometimes adjusted kidney function estimates based on whether a person was identified as Black or non-Black, but this approach could overestimate kidney function and potentially delay care.
Newer race-free eGFR equations, along with cystatin C testing when available, offer a better path forward. The most accurate approach may involve using both creatinine and cystatin C, especially when eGFR results are close to important medical decision points.
For anyone living with kidney disease, understanding how kidney function is measured can help support better conversations with healthcare providers and more informed care decisions.
