mCC/eGFR Ratio: A New Indicator of Muscle Mass and Mortality Risk in ICU Patients, Study Finds

The findings showed that the mCC/eGFR ratio correlates with both in-hospital and long-term mortality, making it a readily accessible measure of muscle mass in ICU patients.

"In-hospital mortality rates were 27% for patients in the lowest mCC/eGFR quartile, compared to just 11% in the highest quartile. Five years after discharge, the mortality rate remained elevated at 37% for those in the lowest quartile, while it dropped to 19% for those in the highest," the researchers reported. 

Muscle mass is a critical factor in the health of ICU patients, influencing their recovery trajectory and overall prognosis. Loss of muscle mass, or cachexia, is commonly observed in critically ill individuals, and it has been linked to poorer outcomes. While muscle mass can be assessed using 24-hour urinary creatinine excretion (UCE), its effectiveness for predicting risk in individual patients is hindered by the absence of age-, sex-, weight-, and length-specific reference values for UCE. The ratio of measured creatinine clearance (mCC) to estimated glomerular filtration rate (eGFR) may help address this limitation.

In response to these insights, Meint Volbeda, Department of Critical Care, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands, and colleagues aimed to evaluate the relationship between the mCC/eGFR ratio in ICU patients and both all-cause hospital mortality and long-term mortality.

For this purpose, the researchers calculated the mCC/eGFR ratio in patients admitted to the ICU between 2005 and 2021, specifically those with KDIGO acute kidney injury (AKI) stages 0–2 and an ICU stay of 24 hours or longer. The mCC was derived from urinary creatinine excretion and plasma creatinine levels, then indexed to 1.73 m². The mCC/eGFR was analyzed by dividing patients into quartiles and treating it as a continuous variable.

The study led to the following findings:

• A total of 7,509 patients were studied (average age 61 years; 38% female).
• In-hospital mortality was 27% for those in the lowest mCC/eGFR quartile, compared to just 11% in the highest quartile.
• Five years after hospital discharge, mortality was 37% in the lowest quartile and 19% in the highest.
• The mCC/eGFR ratio, when treated as a continuous variable, was independently linked to in-hospital mortality in multivariable logistic regression, with an odds ratio of 0.578. This ratio was significantly related to five-year post-discharge mortality in Cox regression analysis, with a hazard ratio of 0.27.

The authors suggest that the mCC/eGFR ratio could be a valuable tool for estimating overall muscle mass in ICU patients, irrespective of demographic factors, and is independently associated with both in-hospital and long-term mortality.

"Future studies may further clarify the utility of the mCC/eGFR ratio in clinical practice," they concluded.

Reference:

Volbeda, M., Zijlstra, H.W., Post, A. et al. Creatinine clearance/eGFR ratio: a simple index for muscle mass related to mortality in ICU patients. BMC Nephrol 25, 330 (2024). https://doi.org/10.1186/s12882-024-03760-2