Researchers at Karolinska Institutet have found that even kidney test results within the normal range can signal future chronic kidney disease if they are low for a person's age. The study, based on data from over 1.1 million adults in Stockholm, introduces reference charts and an online tool to help doctors identify at-risk patients earlier. This could prevent serious damage, as kidney disease often goes undetected until half of kidney function is lost.
Chronic kidney disease affects 10 to 15 percent of adults worldwide and is projected to become one of the top five causes of years of life lost by 2040. A major issue is late diagnosis, with many patients only identified after more than half their kidney function has declined, limiting treatment options. To address this, scientists from Karolinska Institutet analyzed nearly seven million estimated glomerular filtration rate (eGFR) tests from 2006 to 2021, covering about 80 percent of Stockholm residents aged 40 to 100.
The team created population-based reference charts for eGFR, comparing an individual's results to age- and sex-matched norms rather than fixed cutoffs. This method, inspired by pediatric growth charts, aims to spot subtle risks sooner. "We were inspired by the growth and weight charts used in pediatrics, which intuitively help clinicians identify children at risk of obesity or undergrowth," said Yuanhang Yang, the study's first author and a postdoctoral researcher at Karolinska Institutet.
Key findings link lower eGFR percentiles to worse outcomes. People below the 25th percentile faced higher risks of kidney failure needing dialysis or transplantation. A U-shaped pattern emerged for mortality, with both very low and very high percentiles associated with increased death risk. Yet, clinical practice lags: only one in four individuals with eGFR above 60 ml/min/1.73 m² but below the 25th percentile received urinary albumin testing, crucial for early detection.
For instance, a 55-year-old woman with an eGFR of 80 might seem fine, but it places her in the 10th percentile for her age, tripling her future dialysis risk. "This signals an opportunity to act earlier," noted Juan Jesús Carrero, a professor at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet.
The researchers developed a free online calculator by PhD student Antoine Creon to integrate these charts into routine care. Funded by entities like the Swedish Research Council and part of the SCREAM project, the study reports no conflicts of interest. Published in Kidney International, it underscores the need for age-adjusted evaluations to enable prevention.
