Sarcopenia Strongly Affects Serum Levels of Cystatin C in Patients with Heart Failure

Introduction Low muscle mass, or sarcopenia, is commonly seen in patients with heart failure (HF). For any given level of renal function, patients with sarcopenia will have lower levels of serum creatinine because there is less muscle mass to produce creatinine. Thus, the use of creatinine to estimate glomerular filtration rate (GFR) is affected by sarcopenia. In contrast to creatinine, cystatin C is considered a better filtration marker to estimate GFR in the setting of sarcopenia because it not seclusively produced by muscle. However, it has not been demonstrated that serum cystatin C levels are independent of sarcopenia in patients with HF. Hypothesis Serum cystatin C levels will be minimally influenced by muscle mass in patients with heart failure. Methods Serum cystatin C and serum creatinine were measured in patients with decompensated heart failure. Strict timed urine collections were used to measure creatinine excretion rate. Muscle mass was estimated with a validated equation based on urine creatinine excretion (Heymsfield). Creatinine clearance was calculated and used as a surrogate for measured GFR. Results Out of the 295 patients analyzed (average age 65 ±14 years), 65% were male and 61% were obese. Baseline levels of serum creatinine were 1.5±0.6 mg/dL and cystatin C were 1.7±0.7 mg/L. In univariate analysis, serum cystatin C showed a negative correlation with muscle mass (rho -0.37, p Conclusion Serum cystatin C serum levels are strongly associated with muscle mass in patients with HF. This may lead to inaccuracies when cystatin C is used to estimate GFR.