A massive Swedish study suggests that “normal” kidney test results can still hide early risk. A new web-based tool could help clinicians act years sooner to prevent chronic kidney disease.
Subtle changes in kidney function that still fall within the normal range may be an early warning sign of chronic kidney disease, according to a major new study from Karolinska Institutet in Sweden. The researchers have turned that insight into a simple web-based tool that could help doctors spot trouble years before patients feel sick.
Chronic kidney disease is a growing global health problem, affecting an estimated 10-15% of adults worldwide. Because there are no broad screening programs, many people are diagnosed only after they have already lost more than half of their kidney function, when damage is harder to reverse and the risk of dialysis or transplant rises sharply.
The new study, published in the journal Kidney International, focuses on estimated glomerular filtration rate, or eGFR, the standard lab measure of how well the kidneys filter blood. Instead of looking only at whether a patient’s eGFR falls above or below a fixed cutoff, the team asked how that value compares with others of the same age and sex.
To answer that, they built detailed, population-based charts of eGFR using health records from more than 1.1 million adults in the Stockholm region of Sweden. The data set, drawn from nearly 7 million eGFR tests performed between 2006 and 2021, covered about 80% of residents ages 40 to 100.
The researchers then examined how far each person’s eGFR was from the median for their age and sex, and tracked health outcomes over time. People whose kidney function was lower than most of their peers, even if still technically normal, faced higher risks.
Those with an eGFR below the 25th percentile for their age and sex had a markedly greater chance of progressing to kidney failure that required dialysis or transplantation. The study also found a U-shaped pattern for death risk: both unusually low and unusually high eGFR percentiles were linked to increased mortality.
To make these findings usable in everyday practice, the team translated their charts into an online calculator for clinicians, which was developed by doctoral student Antoine Creon. By entering a patient’s age, sex and eGFR, a doctor can see where that person falls on the population curve and whether extra follow-up might be warranted.
“We were inspired by the growth and weight charts used in paediatrics, which intuitively help clinicians identify children at risk of obesity or undergrowth,” first author Yuanhang Yang, a postdoctoral researcher in Karolinska Institutet’s Department of Clinical Science and Education at Södersjukhuset, said in a news release.
The study also highlights how easily early warning signs can be missed. Among people whose eGFR values were above 60 milliliters per minute per 1.73 square meters — a level many clinicians would consider reassuring — but still fell below the 25th percentile for their age, only about one in four had been given a follow-up urine test for albumin. That test is important for detecting early kidney damage.
Senior author Juan Jesús Carrero, a professor in Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics, illustrated what is at stake.
“For example, consider a 55-year-old woman with an eGFR of 80. Most clinicians would not react to such a seemingly normal value. However, our charts show that this corresponds to the 10th percentile for women of that age, and that she has a three-fold higher risk of starting dialysis in the future. This signals an opportunity to act earlier,” he said in the news release.
By reframing eGFR as a percentile rather than a simple pass-or-fail number, the researchers hope to nudge health systems toward primary prevention. People flagged as being at higher risk could receive closer monitoring, blood pressure and diabetes management, lifestyle counseling, and timely referrals to kidney specialists, potentially slowing or preventing disease progression.
The work is part of the SCREAM project, a large effort to use real-world health data to improve kidney care.
The team’s conclusion is that the way kidney function is interpreted may be just as important as the test itself.
For now, the web-based calculator and open eGFR charts are intended for health professionals, not for self-diagnosis. But if widely adopted, this relatively simple change in perspective could help shift kidney disease care from reacting late to acting early, giving millions more people a chance to protect their kidney health before it is too late.
Source: Karolinska Institutet