In patients with nondialysis chronic kidney disease, higher creatinine muscle index was independently associated with lower odds of probable sarcopenia and reduced all-cause mortality prior to kidney replacement therapy, according to a prospective cohort study published in PLOS Medicine.
Thomas McDonnell, MBChB, of the Donal O’Donoghue Renal Research Centre, Salford Royal Hospital, United Kingdom, and colleagues evaluated 2,930 patients enrolled in the UK-based NURTuRE-CKD study across 16 nephrology centers. Patients had an estimated glomerular filtration rate of 15 to 59 mL/min/1.73 m² or at least 60 mL/min/1.73 m² with albuminuria. Median age was 66 years, and median estimated glomerular filtration rate was 34 mL/min/1.73 m².
Creatinine muscle index was calculated using cystatin C–based estimated glomerular filtration rate multiplied by serum creatinine.
At baseline, 28% of patients met European Working Group on Sarcopenia in Older People 2 criteria for probable sarcopenia, defined by low handgrip strength. Over a median follow-up of 50 months, 18% of patients died prior to kidney replacement therapy initiation.
In multivariable analyses stratified by sex and adjusted for demographic and clinical factors, each 100 mg/day per 1.73 m² increase in creatinine muscle index was associated with 28% lower odds of probable sarcopenia in men and 19% lower odds in women. These associations were consistent across age and body mass index subgroups.
Higher creatinine muscle index also correlated with greater grip strength and better performance on timed get-up-and-go testing. In adjusted models, each 100 mg/day per 1.73 m² increase in creatinine muscle index was associated with approximately 1 kg greater grip strength in men and 1 kg greater grip strength in women.
In Cox proportional hazards models, higher creatinine muscle index was associated with reduced mortality risk. Each 100 mg/day per 1.73 m² increase corresponded to a 15% lower risk of death in men and a 23% lower risk in women prior to kidney replacement therapy initiation. The association appeared largely linear across creatinine muscle index levels.
Discriminative analyses showed that creatinine muscle index performed better than creatinine–cystatin C ratio and difference measures in identifying patients with probable sarcopenia and predicting mortality.
The researchers noted several limitations, including the observational design, lack of direct muscle mass measurement, and restriction to secondary care chronic kidney disease populations, which may limit generalizability.
“Given its ease of measurement and strong associations with clinically meaningful outcomes, creatinine muscle index warrants further investigation as a tool to enhance risk stratification and identify patients at the highest risk of sarcopenia-related complications so that targeted interventions can be undertaken,” Dr. McDonnell and colleagues wrote.
Funding for the study was provided by commercial partners to the charity Kidney Research UK. Dr. McDonnell reported no disclosures. Other researchers reported receiving grant support, honoraria, or consulting fees from several pharmaceutical companies.
Source: PLOS Medicine
