Abstract
Sarcopenia is highly prevalent in patients with advanced chronic kidney disease (CKD), yet a reliable serum index has not been established. The product of serum creatinine and the estimated glomerular filtration rate based on cystatin C (Cr×eGFRcys) was recently proposed as a sarcopenia index (SI), approximately to 24-h filtered creatinine through the glomerulus. We aimed to evaluate the diagnostic validity of the novel SI in advanced CKD. In 297 patients with non-dialysis stage 3b-5 CKD, aged 68.8 ± 12.9 years, the total skeletal muscle mass (SMM), handgrip strength (HGS), and usual gait speed were assessed. Sarcopenia was defined based on the Asian Working Group for Sarcopenia 2019 consensus update. The prevalence of sarcopenia in this cohort was 20.2%. The SI correlated moderately with SMM (r = 0.503, P < 0.001), HGS (r = 0.508, P < 0.001), and gait speed (r = 0.381, P < 0.001); the independency of the SI with three muscle metrics was confirmed after extensive adjustment. For sarcopenia prediction, the SI had acceptable discriminative powers in males [area under the receiver operating characteristic curve (AUC) 0.646, 95% confidence interval (CI) 0.569–0.718] and females (AUC 0.754, 95% CI 0.670–0.826). In males, the best cut-off was 53.9, which provided 71.1% sensitivity, 58.0% specificity, 32.9% positive predictive value (PPV), and 87.4% negative predictive value (NPV); in females, the best cut-off was 45.8, which provided 81.8% sensitivity, 62.3% specificity, 31.0% PPV, and 94.3% NPV. In conclusion, Cr×eGFRcys could be served as a surrogate marker for sarcopenia and may be helpful for sarcopenia screening in advanced CKD. Further studies are needed to expand our investigation.
Highlights
Sarcopenia, which is characterized by a progressive decline of skeletal muscle mass, strength, and physical performance, is frequently observed in patients with chronic kidney disease (CKD) and leads to poor clinical outcomes [1,2,3], as pathogenic factors—metabolic acidosis, inflammation, impaired insulin signaling, oxidative stress, accumulated uremic toxins, suppressed appetite, decline in satellite cells, and myostatin overexpression—accelerate skeletal muscle wasting as kidney disease progresses [4, 5].Novel Sarcopenia Index in CKDsarcopenia is a major concern in patients with advancedstage CKD
Creatinine is a metabolite of creatine phosphate that is converted non-enzymatically from skeletal muscle, and the endogenous creatinine generation rate depends on skeletal muscle mass under steady renal function [11, 12]
The correlation coefficients with muscle measures and the discriminatory power for sarcopenia exhibited by sarcopenia index (SI) were similar to the performance of 24-h urine creatinine excretion (Ucr)
Summary
Sarcopenia, which is characterized by a progressive decline of skeletal muscle mass, strength, and physical performance, is frequently observed in patients with chronic kidney disease (CKD) and leads to poor clinical outcomes [1,2,3], as pathogenic factors—metabolic acidosis, inflammation, impaired insulin signaling, oxidative stress, accumulated uremic toxins, suppressed appetite, decline in satellite cells, and myostatin overexpression—accelerate skeletal muscle wasting as kidney disease progresses [4, 5].Novel Sarcopenia Index in CKDsarcopenia is a major concern in patients with advancedstage CKD. Protein restriction is usually implemented in patients with advanced-stage CKD to attenuate renal progression, and clinical supervision of nutritional status is highly recommended [6]. Imaging modalities including bioelectrical impedance, ultrasound, dual-energy X-ray absorptiometry, computed tomography, and magnetic resonance imaging, as well as D3-creatine dilution, are strongly recommended by expert panels as measurement tools for skeletal muscle mass [7,8,9,10], yet are not always available in outpatient settings. Surrogate markers for the early detection of sarcopenia in advanced-stage CKD are in demand. Due to its properties of free glomerular filtration and minimal tubular reabsorption, timed urine creatinine excretion (Ucr) is a reliable marker for predicting skeletal muscle mass in various populations [13,14,15,16]. The collection of 24-h urine samples is inconvenient. Under- or over-collection of urine samples is common
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