Researchers in the United Kingdom have discovered that a simple combination of two common blood tests can help identify a serious and often overlooked complication of chronic kidney disease.
The condition, called sarcopenia, involves the loss of muscle mass and strength and is linked to a higher risk of death and poorer quality of life.
The study, led by scientists from The University of Manchester and Northern Care Alliance NHS Foundation Trust, found that a measure called the creatinine muscle index, or CMI, can reliably detect sarcopenia in people with chronic kidney disease.
Their findings were published in the journal PLOS Medicine.
Sarcopenia can make everyday tasks more difficult, reduce mobility, and increase the risk of falls, hospitalizations, and early death.
It is especially common in people with chronic kidney disease, yet it often goes unnoticed until it becomes severe.
Early detection is important because treatments such as strength training and improved nutrition can help slow or even reverse muscle loss.
The new test uses two routine blood markers already measured in kidney care: creatinine and cystatin C. Both are used to assess kidney function, but they behave differently.
Creatinine levels are influenced by muscle mass, while cystatin C is not. By comparing the two, researchers can estimate how much muscle a person has and identify those at risk of sarcopenia.
Scientists were initially unsure whether this method would work in people with kidney disease because the condition affects how creatinine is processed in the body. However, the study showed that CMI still accurately reflected muscle health and survival risk in these patients.
The research involved nearly 3,000 adults with chronic kidney disease who were not yet on dialysis. Participants were recruited from 16 kidney centers across the United Kingdom and followed for more than four years. Researchers measured their muscle strength using hand grip tests and assessed walking speed, both key indicators of physical function.
Results showed that lower CMI scores were strongly linked to weaker grip strength, slower walking speed, and a higher likelihood of sarcopenia. Patients with higher CMI scores had a lower risk of death during the study period. For every increase in CMI, the risk of death dropped significantly for both men and women.
Experts say the findings could change how doctors monitor patients with chronic kidney disease. Because the test relies on blood samples already collected during routine care, it could be easily added without extra procedures. Early identification of muscle loss would allow doctors to recommend exercise programs, dietary changes, or other treatments sooner, potentially improving long-term outcomes.
Researchers emphasize that sarcopenia is not just a natural part of aging but a serious health issue that can be managed if detected early. The new test offers a practical way to identify vulnerable patients and provide support before the condition becomes severe.
If adopted widely, the creatinine muscle index could help improve survival and quality of life for people living with chronic kidney disease, highlighting the importance of muscle health as part of overall medical care.
