Research shows that hospitals should switch from the outdated MDRD equation to the newer CKD-EPI 2009 equation for measuring kidney function. According to Gram Research analysis of 1,438 patients, the old MDRD equation misses early kidney disease in people with relatively good kidney function, while CKD-EPI 2009 is significantly more accurate and causes minimal disruption when hospitals make the switch.
Doctors use special math equations to measure how well your kidneys are filtering waste from your blood. This is called your glomerular filtration rate, or eGFR. According to Gram Research analysis, scientists tested three different equations on 1,438 patients to see which one gives the most accurate results. They found that the older equation doctors have been using isn’t as good at spotting kidney problems in people with healthier kidneys. Two newer equations worked much better, with one being especially reliable for hospitals. This matters because getting the right measurement helps doctors catch kidney disease early and treat it properly.
Key Statistics
A 2026 study of 1,438 hospital patients found that the MDRD equation, which has been used for years, shows limited accuracy for patients with kidney function above 80 mL/min/1.73 m², potentially missing early kidney disease cases.
According to research reviewed by Gram, the CKD-EPI 2009 equation demonstrated the strongest agreement with clinical kidney disease staging compared to three other equations tested on 1,438 patients in 2026.
A 2026 comparative analysis of 1,438 patients found that the EKFC equation reclassified approximately 12% of patients into more advanced kidney disease stages compared to the standard MDRD equation.
Research from 2026 involving 1,438 patients showed that CKD-EPI 2009 proved to be the most suitable alternative to MDRD-IDMS for hospital implementation due to balanced impact on kidney disease stage classification.
The Quick Take
- What they studied: Which math formula doctors should use to measure how well kidneys are filtering blood and removing waste
- Who participated: 1,438 hospital patients (886 men and 552 women, average ages 60 and 63 years) with different types of kidney health conditions
- Key finding: The old equation doctors have been using (MDRD) doesn’t work as well for people with healthier kidneys. Two newer equations (CKD-EPI 2009 and EKFC) give more accurate results, with CKD-EPI 2009 being the best choice for most hospitals.
- What it means for you: If your doctor checks your kidney function, they may get a more accurate result if they switch to the newer equation. This could help catch kidney problems earlier, though your doctor will still need to consider your overall health picture.
The Research Details
Researchers looked back at test results from 1,438 patients who had visited their hospital. They took the same blood test results and ran them through four different mathematical equations that doctors use to estimate kidney function. These equations are like different recipes that use the same ingredients (blood measurements) but combine them differently to get a final number.
The four equations they tested were: MDRD (the old standard), CKD-EPI 2009 (a newer version), CKD-EPI 2021 (the newest version), and EKFC (a European version). By comparing how each equation classified the same patients, they could see which one was most accurate and which one would cause the fewest changes if hospitals switched to using it.
This type of study is called a retrospective comparison because researchers looked backward at existing data rather than following new patients forward over time. It’s a practical way to test whether switching to a new equation would actually help doctors in real hospitals.
Kidney disease is a serious problem that’s getting worse. By 2040, it’s expected to be one of the top five causes of death worldwide. The earlier doctors can catch kidney problems, the better they can treat them and slow down the disease. But they can only catch problems if they’re using the most accurate measurement tools. An outdated equation might miss kidney disease in people who still have relatively good kidney function, which means they wouldn’t get treatment when it could help the most.
This study looked at real patients in a real hospital, which makes the results practical and useful. The large sample size of 1,438 patients gives confidence that the patterns they found aren’t just random luck. However, because this was a retrospective study using existing data, researchers couldn’t control all the factors that might affect results. The study was done at one hospital, so results might be slightly different in other hospitals with different patient populations. The researchers were transparent about what they were testing and why, which is a good sign of quality research.
What the Results Show
The old MDRD equation, which hospitals have been using for years, has a major weakness: it doesn’t work well when kidney function is relatively good (above 80 mL/min/1.73 m²). This means it might miss early kidney disease in people who still have decent kidney function.
The CKD-EPI 2009 equation performed the best overall. It gave results that matched closely with the MDRD equation for patients with more advanced kidney disease, but it was much more accurate for patients with better kidney function. When researchers looked at how patients would be classified into different kidney disease stages, CKD-EPI 2009 made very few changes compared to MDRD, meaning hospitals could switch to it without causing confusion.
The EKFC equation also worked well and was more accurate than MDRD, but it reclassified about 12% of patients into more advanced kidney disease stages. This means if hospitals switched to EKFC, they would identify more people as having kidney disease than they currently do. While this might catch more cases early, it could also worry patients unnecessarily and require more follow-up testing.
The newest CKD-EPI 2021 equation gave higher kidney function numbers than the others, which could potentially miss some kidney disease cases.
The study showed that different equations can give very different results for the same patient. Some patients who would be classified as having normal kidney function with one equation might be classified as having early kidney disease with another. This highlights how important it is to use the right equation, because it directly affects how doctors diagnose and treat kidney disease. The researchers also found that the choice of equation matters more for some groups of patients than others, particularly those with better kidney function.
This research confirms what other scientists have been saying: the MDRD equation is outdated and needs to be replaced. Previous studies had suggested that newer equations were more accurate, but this study shows exactly how much better they are in a real hospital setting with diverse patients. The findings support the move toward CKD-EPI equations that many hospitals and countries have already started making. This study adds practical evidence that hospitals don’t need to worry too much about switching from MDRD to CKD-EPI 2009, because it won’t dramatically change how they classify most patients.
This study only looked at patients from one hospital, so the results might be different in other hospitals with different types of patients. The researchers couldn’t test whether using the new equation actually led to better patient outcomes—they only tested whether the equations gave different numbers. The study was done in 2026, so the patient population and medical practices might change over time. Additionally, the researchers didn’t have information about whether patients had other health conditions that might affect kidney function, which could have influenced the results.
The Bottom Line
If you have your kidney function tested, ask your doctor which equation they’re using to calculate your eGFR. If they’re still using the old MDRD equation, you might ask whether they’ve considered switching to CKD-EPI 2009, which is more accurate. However, don’t panic if you get a different number with a new equation—it doesn’t necessarily mean your kidneys got worse; it might just mean the new measurement is more accurate. This research is most relevant for hospitals and laboratories deciding which equation to use, rather than for individual patients making health decisions.
This research matters most for: hospital laboratories and doctors deciding which equation to use for kidney function testing; people with kidney disease who want to understand their test results better; people at risk for kidney disease (those with diabetes, high blood pressure, or a family history of kidney disease); and healthcare administrators making decisions about lab equipment and procedures. It’s less directly relevant for people with completely healthy kidneys, though everyone should know that kidney disease is common and early detection is important.
If your hospital switches to a new equation, you might see a change in your eGFR number on your next test. However, this change in the number doesn’t mean your kidney function changed—it just means they’re measuring it differently. The real benefit of using a more accurate equation is that kidney disease will be caught earlier, which means treatment can start sooner and potentially prevent more kidney damage over months and years.
Frequently Asked Questions
What does eGFR mean and why is it important?
eGFR stands for estimated glomerular filtration rate—it’s a number that shows how well your kidneys are filtering waste from your blood. It’s important because it helps doctors diagnose kidney disease early, when treatment can be most effective. A lower eGFR means your kidneys aren’t working as well.
Should I be worried if my doctor switches my kidney function equation?
Not necessarily. If your doctor switches from MDRD to CKD-EPI 2009, your eGFR number might change slightly, but this reflects a more accurate measurement, not a change in your actual kidney function. Ask your doctor to explain what the new number means for your health.
How often should I get my kidney function tested?
If you have risk factors like diabetes, high blood pressure, or a family history of kidney disease, ask your doctor about annual testing. People with normal kidney function and no risk factors may need less frequent testing. Your doctor can recommend the right schedule for you.
Can kidney disease be reversed if caught early?
Early detection allows doctors to slow kidney disease progression significantly through medication, lifestyle changes, and careful management of blood pressure and blood sugar. While some kidney damage can’t be reversed, catching disease early prevents further damage and helps preserve remaining kidney function.
What can I do to protect my kidney function?
Control blood pressure and blood sugar if you have diabetes, limit salt intake, stay hydrated, maintain a healthy weight, avoid excessive alcohol, don’t smoke, and take medications as prescribed. Regular kidney function testing helps monitor your progress and catch problems early.
Want to Apply This Research?
- Track your eGFR number from each kidney function test along with the date and which equation was used to calculate it. Note any changes in the equation your doctor uses, so you can understand whether changes in your number reflect actual changes in kidney function or just a switch to a more accurate measurement method.
- If your eGFR is lower than you’d like, use the app to set reminders for regular kidney function testing (usually annually for people at risk), track your blood pressure and blood sugar if you have diabetes or high blood pressure, and log any medications your doctor prescribes for kidney health. You can also use the app to track lifestyle changes like reducing salt intake and staying hydrated.
- Set up quarterly or annual reminders to review your eGFR trend over time. Create a chart in the app showing your eGFR numbers and dates, so you can see whether your kidney function is stable, improving, or declining. Share this information with your doctor at each visit to help them make the best treatment decisions.
This research compares different laboratory equations for measuring kidney function and is primarily relevant for healthcare providers and laboratories making testing decisions. If you have concerns about your kidney function or have been diagnosed with kidney disease, consult with your doctor or a kidney specialist (nephrologist) for personalized medical advice. Do not use this information to self-diagnose or change your treatment without professional medical guidance. The findings of this study do not constitute medical advice and should not replace consultation with qualified healthcare professionals.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.