Even seemingly normal kidney function test results may not tell the whole story, according to new research published in Kidney International. A study from Karolinska Institutet suggests that subtle declines in kidney function, even within the range considered “normal” by standard clinical guidelines, can signal an increased risk of developing chronic kidney disease and experiencing poorer health outcomes.
Chronic kidney disease affects an estimated 10-15% of adults worldwide and is projected to become one of the five leading causes of years of life lost by . A significant challenge in managing this growing health problem is late diagnosis. Many patients aren’t diagnosed until they’ve already lost more than half of their kidney function, at which point treatment options become limited.
Rethinking the “Normal” Range
Traditionally, kidney health is assessed using the estimated glomerular filtration rate (eGFR), a measure of how well the kidneys filter waste from the blood. Current clinical practice often relies on a single cutoff value to determine whether an eGFR is normal. However, the Karolinska Institutet study proposes a more nuanced approach. Researchers developed population-based reference charts that compare an individual’s eGFR to that of others of the same age and sex.
“Instead of simply labeling a result as ‘normal’ or ‘abnormal,’ these charts allow clinicians to see where a patient’s kidney function falls within the spectrum of what’s typical for their age group,” explains Yuanhang Yang, a postdoctoral researcher at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet.
A Web-Based Tool for Clinical Use
To facilitate this new approach, the research team has created a freely available web-based calculator. Developed by PhD student Antoine Creon, the tool allows healthcare professionals to quickly assess how a patient’s eGFR compares to population norms. The calculator is intended to support clinical decision-making and encourage earlier intervention.
The study itself was based on analysis of health data from over 1.1 million adults in the Stockholm region of Sweden, representing approximately 80% of residents aged 40 to 100. Researchers analyzed nearly seven million eGFR test results collected between and to establish detailed distributions by age and sex.
Lower Percentiles, Higher Risk
The findings revealed a clear correlation between kidney function levels and health outcomes. Individuals whose eGFR fell below the 25th percentile for their age and sex faced a significantly higher risk of progressing to kidney failure requiring dialysis or transplantation. The researchers also observed a U-shaped pattern in relation to mortality, indicating that both unusually low and unusually high eGFR percentiles were associated with an increased risk of death.
Missed Opportunities for Early Detection
The study also highlighted a potential gap in current clinical practice. Among patients with an eGFR above 60 ml/min/1.73 m2 – a value often considered within the normal range – approximately one in four had not undergone additional testing for urinary albumin. This test is crucial for detecting early kidney damage and guiding timely intervention.
“For example, consider a 55-year-old woman with an eGFR of 80,” says Juan Jesús Carrero, professor at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet. “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.”
This suggests that a more proactive approach, utilizing age- and sex-specific reference charts and considering even subtly reduced kidney function, could lead to earlier diagnosis and potentially slow the progression of chronic kidney disease.
The Importance of Early Intervention
The research underscores the importance of identifying individuals at risk of developing chronic kidney disease before significant damage occurs. Early intervention, including lifestyle modifications and management of underlying conditions like diabetes and hypertension, can help preserve kidney function and improve long-term health outcomes. The new tool developed by the Karolinska Institutet team aims to empower clinicians to make more informed decisions and prioritize preventive care for their patients.
The study was part of the SCREAM project and received funding from the Swedish Research Council, the Swedish Heart-Lung Foundation, Region Stockholm, and the Swedish Kidney Foundation. The researchers reported no conflicts of interest.
