Discrepancy in Kidney Tests Signals Higher Health Risks

A recent study highlights a significant health concern: a mismatch between two common kidney function tests could indicate an increased risk for kidney failure, heart disease, and mortality. This research, led by scientists at NYU Langone Health, underscores the importance of using both creatinine and cystatin C measurements to assess kidney health comprehensively.

Traditionally, healthcare providers have relied on blood levels of creatinine to evaluate how effectively kidneys filter waste from the bloodstream. However, newer guidelines recommend that levels of cystatin C, a protein produced by all cells, be used alongside creatinine. These two tests respond differently to various factors, including age and certain diseases. The study reveals that relying on only one of these tests could leave significant gaps in understanding a patient’s kidney function.

In a global analysis involving over 860,966 participants, researchers found that more than one-third of hospitalized individuals exhibited a cystatin C reading at least 30% lower than their creatinine levels. This discrepancy may serve as an early warning sign of future health issues.

Dr. Morgan Grams, a co-corresponding author of the study, stated, “Our findings highlight the importance of measuring both creatinine and cystatin C to gain a true understanding of how well the kidneys are working.” He emphasized that utilizing both biomarkers could identify a larger number of individuals with compromised kidney function, especially among older and more vulnerable populations.

The study’s results will be published online on November 7, 2025, in the journal JAMA and will be presented at the annual Kidney Week conference organized by the American Society of Nephrology. The implications of this research extend beyond just detecting kidney issues; accurate kidney assessment is vital for determining appropriate dosages of various medications, including cancer treatments and antibiotics.

In a related investigation, the same research team reported a concerning statistic: chronic kidney disease has become the ninth leading cause of death globally. Early detection methods, such as those highlighted in this study, can lead to timely interventions and potentially avoid more drastic measures like dialysis or organ transplants.

Researchers analyzed comprehensive healthcare records, blood tests, and demographic data from participants of multiple nationalities. Each individual had both their creatinine and cystatin C levels measured on the same day, followed by an average follow-up period of 11 years. The analysis took into account non-kidney-related factors that could influence these test results, such as smoking, obesity, and cancer history.

The study is a significant contribution from the Chronic Kidney Disease Prognosis Consortium, which aims to refine the understanding and treatment of chronic kidney disease. Their findings indicate that individuals whose cystatin C measures were at least 30% lower than their creatinine readings faced a heightened risk of death, heart disease, and heart failure.

Despite the potential benefits of cystatin C testing—first recommended in 2012—a 2019 survey revealed that fewer than 10% of clinical laboratories in the United States offered the test in-house. Major laboratories, including Quest Diagnostics and Labcorp, have since begun providing it.

Dr. Josef Coresh, another study co-corresponding author, remarked, “These results underscore the need for physicians to take advantage of the fact that more hospitals and healthcare providers are starting to offer cystatin C testing.” He cautioned that among the hospitalized patients in this study, fewer than 1% had undergone cystatin C testing, indicating a missed opportunity for enhanced patient care.

The study not only emphasizes the need for a dual approach in kidney function assessment but also highlights the evolving landscape of chronic kidney disease diagnosis and treatment. With the increasing prevalence of this condition, understanding how to effectively monitor and manage kidney health is more critical than ever.