A Novel Application of Serum Creatinine and Cystatin C to Predict Sarcopenia in Advanced CKD

Association between sarcopenia index and the risk of second hip fracture in older adults

BACKGROUND

The sarcopenia index (SI), calculated as the ratio of serum creatinine to cystatin C level, represents skeletal muscle mass and strength. This study aimed to investigate the association between SI and the risk of second hip fractures, considering various demographic and clinical factors to improve second hip fracture risk prediction.

METHODS

This prospective cohort study included older adults with low-energy hip fractures who were monitored for at least two years to track the incidence of subsequent hip fractures. Baseline demographic, clinical, and biochemical data were collected. The SI was calculated as serum creatinine [mg/dL]/cystatin C [mg/L]) × 100. Logistic regression models were used to evaluate the relationship between the SI and the risk of a second hip fracture. Subgroup analyses were conducted to assess the effects of potential modifiers, including gender, body mass index, hypertension, diabetes, and estimated glomerular filtration rate. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the predictive performance of SI.

RESULTS

A total of 637 patients were included, 59 of whom experienced a second hip fracture during the follow-up period. The patients with second hip fracture exhibited significantly lower SI levels than those without (48.93 ± 8.54 versus 62.95 ± 14.39, P < 0.001). Logistic regression analysis revealed a significant association between a lower muscle-reduction index and an increased risk of a second hip fracture in the fully adjusted model (odds ratio: 0.91; 95% confidence interval: 0.87-0.94; P < 0.001). The area under the ROC curve for predicting a second hip fracture based on the SI was 0.822, indicating good predictive accuracy. Furthermore, subgroup analyses revealed that SI was inversely associated with second hip fracture.

CONCLUSIONS

The SI serves as a significant predictor of second hip fractures in older adults, even after considering age, gender, and clinical factors.

Combating chronic kidney disease-associated cachexia: A literature review of recent therapeutic approaches

In 2008, the Society on Sarcopenia, Cachexia, and Wasting Disorders introduced a generic definition for all types of cachexia: "a complex metabolic syndrome associated with the underlying illness characterized by a loss of muscle, with or without fat loss". It is well-known that the presence of inflammatory burden in end-stage renal disease (ESRD) patients may lead to the evolution of cachexia. Since the etiology of cachexia in chronic kidney disease (CKD) is multifactorial, thus the successful treatment must involve several concomitant measures (nutritional interventions, appetite stimulants, and anti-inflammatory pharmacologic agents) to provide integrated effective therapeutic modalities to combat causative factors and alleviate the outcomes of patients. Given the high mortality rate associated with cachexia, developing new therapeutic modalities are prerequisite for ameliorating patients with CKD worldwide. The present review aims to discuss some therapeutic strategies and provide an update on advances in nutritional approaches to counteract cachexia.

Sarcopenia in Chronic Kidney Disease: A Narrative Review from Pathophysiology to Therapeutic Approaches

Chronic kidney disease (CKD) is a progressive condition linked to sarcopenia, a syndrome characterized by loss of skeletal muscle mass and strength, affecting a quarter of CKD patients globally. Sarcopenia has multiple paths through which it can worsen morbidity and mortality as well as decrease the quality of life in CKD, including systemic inflammation, hormonal imbalances, metabolic changes, and dysbiosis of gut microbiota. There is a regional variation in the criteria set for diagnosis, with two main groups being the European Working Group on Sarcopenia in Older People and the Asian Working Group for Sarcopenia. Management regimes such as nutritional optimization, vitamin D, exercise, correction of metabolic acidosis, and modulation of gut microbiota constitute effective intervention strategies. Emerging therapeutic options include anabolic agents, myostatin inhibitors, and anti-inflammatory treatment options. Future advances such as genomics, proteomics, and personalized medicine will open up new avenues for addressing the complex pathophysiology of sarcopenia. Hence, a comprehensive multidisciplinary approach focused on the specific needs of each patient will be vital in reducing the effects of sarcopenia and improving the situation of people with CKD.

Impact of Serum Creatinine- and Cystatin C-Based Sarcopenia Index on Renal Outcomes in Non-Dialysis-Dependent Chronic Kidney Disease Patients: Results From the KNOW-CKD Study

OBJECTIVE

To evaluate the impact of the serum creatinine- and cystatin C-based new sarcopenia index (SI) on renal outcomes in non-dialysis-dependent patients with chronic kidney disease (CKD).

METHODS

In this observational Korean Cohort Study for Outcome in Patients With CKD (KNOW-CKD), 1957 patients with CKD stage 1 to stage 4 were analyzed from 2011 to 2019. Men and women were separately assigned to quartile groups according to their SI. The primary outcome was a composite renal outcome consisting of 50% reduction in estimated glomerular filtration rate or end-stage kidney disease. With use of Fine and Gray subdistribution hazard models, the association between the SI and the primary outcome was analyzed.

RESULTS

During a median follow-up of 6.0 (4.2 to 7.7) years, the primary composite renal outcome occurred in 528 (28.6%) patients within a median of 3.0 (1.8 to 5.0) years. In unadjusted and adjusted models, lower SI groups had a poor primary outcome compared with the highest group (quartile 4). The hazard ratios for quartiles 1, 2, and 3 compared with quartile 4 in the fully adjusted model were 4.47 (95% CI, 3.05 to 6.56; P<.001), 3.08 (95% CI, 2.13 to 4.48; P<.001), and 2.09 (95% CI, 1.45 to 3.01; P<.001), respectively. Restricted cubic spline regression analyses found a relatively inverse linear relationship between the SI and the composite renal outcome.

CONCLUSION

The new SI is an independent predictor of renal outcomes. A low SI is associated with poor renal outcome.

Serum creatinine and serum cystatin C as an index of muscle mass in adults

PURPOSE OF REVIEW

Serum creatinine reflects both muscle mass and kidney function. Serum cystatin C has recently been recommended as an additional marker for estimating kidney function, and use of both markers together may provide an index of muscle mass. This review aims to describe the biological basis for and recent research examining the relationship of these markers to muscle mass in a range of adult populations and settings.

RECENT FINDINGS

This review identified 67 studies, 50 of which had direct measures of muscle mass, and almost all found relationships between serum creatinine and cystatin C and muscle mass and related outcomes. Most studies have been performed in older adults, but similar associations were found in general populations as well as in subgroups with cancer, chronic kidney disease (CKD), and other morbid conditions. Creatinine to cystatin C ratio was the measure examined the most often, but other measures showed similar associations across studies.

SUMMARY

Measures of serum creatinine and cystatin C together can be an index of muscle mass. They are simple and reliable measures that can be used in clinical practice and research. Further study is needed to determine actionable threshold values for each measure and clinical utility of testing and intervention.

Pathogenesis of Sarcopenia in Chronic Kidney Disease-The Role of Inflammation, Metabolic Dysregulation, Gut Dysbiosis, and microRNA

Chronic kidney disease (CKD) is a progressive disorder associated with a decline in kidney function. Consequently, patients with advanced stages of CKD require renal replacement therapies, such as dialysis and kidney transplantation. Various conditions lead to the development of CKD, including diabetes mellitus, hypertension, and glomerulonephritis, among others. The disease is associated with metabolic and hormonal dysregulation, including uraemia and hyperparathyroidism, as well as with low-grade systemic inflammation. Altered homeostasis increases the risk of developing severe comorbidities, such as cardiovascular diseases or sarcopenia, which increase mortality. Sarcopenia is defined as a progressive decline in muscle mass and function. However, the precise mechanisms that link CKD and the development of sarcopenia are poorly understood. Knowledge about these linking mechanisms might lead to the introduction of precise treatment strategies that could prevent muscle wasting. This review discusses inflammatory mediators, metabolic and hormonal dysregulation, gut microbiota dysbiosis, and non-coding RNA alterations that could link CKD and sarcopenia.

Diagnostic test accuracy of serum creatinine and cystatin C-based index for sarcopenia: a systematic review and meta-analysis

BACKGROUND

Sarcopenia is an important prognostic factor, but its optimal screening methods remain challenging. Several new indices developed based on serum creatinine (Cr) and cystatin C (CysC) have been proposed to be diagnostic biomarkers for sarcopenia screening.

OBJECTIVE

This review aimed to evaluate the diagnostic accuracy of serum Cr- and CysC-based indices for sarcopenia diagnosis.

METHODS

We systematically searched MEDLINE, EMBASE, SCIE and SCOPUS from inception to 2 April 2023. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. A bivariate random-effects model was used to synthesise the pooled sensitivity, specificity and area under the curves of the summary receiver operating characteristic (SROC-AUC).

RESULTS

We retrieved 936 publications and included 16 studies with 5,566 participants (mean age ranged: 51.0-78.4 years, 50.2% men). The prevalence of sarcopenia ranged from 7.8 to 69.5%. All included studies presented a moderate to high risk of bias. The serum Cr- and CysC-based indices showed moderate diagnostic accuracy for sarcopenia (pooled sensitivity: 0.67, 95% CI 0.57-0.75; pooled specificity: 076, 95% CI 0.67-0.83; pooled SROC-AUC: 0.78, 95% CI 0.74-0.81). The Cr/CysC ratio is the most widely studied index, followed by the Cr × eGFRcys index. Overall, both indicators had satisfactory and comparable performance in screening sarcopenia.

CONCLUSION

Serum Cr- and CysC-based indices showed moderate diagnostic accuracy for sarcopenia. The most studied indices-the Cr/CysC ratio and Cr × eGFRcys index-had comparable diagnostic accuracy for evaluating sarcopenia and may serve as surrogate markers for sarcopenia. However, further validation is required to verify these findings.

Blood biomarkers for sarcopenia: A systematic review and meta-analysis of diagnostic test accuracy studies

Biomarkers are emerging as a potential tool for screening or diagnosing sarcopenia. We aimed to summarize the current evidence on the diagnostic test accuracy of biomarkers for sarcopenia. We comprehensively searched Ovid MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials up to January 2023 and only included diagnostic test accuracy studies. We identified 32 studies with 23,840 participants (women, 58.26%) that assessed a total of 30 biomarkers. The serum creatinine to cystatin C ratio (Cr/CysC) demonstrated a pooled sensitivity ranging from 51% (95% confidence interval [CI] 44-59%) to 86% (95% CI 70-95%) and a pooled specificity ranged from 55% (95% CI 38-70%) to 76% (95% CI 63-86%) for diagnosing sarcopenia defined by five different diagnostic criteria (11 studies, 7240 participants). The aspartate aminotransferase to alanine aminotransferase ratio demonstrated a pooled sensitivity of 62% (95% CI 56-67%) and a pooled specificity of 66% (95% CI 60-72%) (3 studies, 11,146 participants). The other 28 blood biomarkers exhibited low-to-moderate diagnostic accuracy for sarcopenia regardless of the reference standards. In conclusion, none of these biomarkers are optimal for screening or diagnosing sarcopenia. Well-designed studies are needed to explore and validate novel biomarkers for sarcopenia.

Validated Tools for Screening Sarcopenia: A Scoping Review

OBJECTIVE

Choosing the optimal sarcopenia screening tool for a specific clinical scenario is challenging. We aimed to summarize all validated sarcopenia screening tools with diagnostic accuracy tested in one or more study populations.

DESIGN

Scoping review.

SETTING AND PARTICIPANTS

Hospitals, nursing homes, communities, or health checkups.

METHODS

We systematically searched 3 databases in April 2022: MEDLINE, EMBASE, and CENTRAL. Two review authors independently performed the study selection and data extraction. The included tools' contents, characteristics, and number of citations were summarized and visualized.

RESULTS

We summarized 102 diagnostic accuracy studies involving 53 screening tools, classified into 7 groups: questionnaires (n = 13); serum biomarkers (n = 10); formulas, algorithms, and models (n = 9); physical ability tests (n = 9); integration tools (n = 7); anthropometric indices (n = 3); and ultrasound or bioimpedance analysis (n = 2). The most commonly used questionnaire was SARC-F (770 citations), followed by SARC-CalF (254 citations) and MSRA-7 (61 citations). Handgrip strength and Ishii score were the most widely used physical performance tests (331 citations) and formulas (294 citations), respectively. Sarcopenia index (based on serum cystatin C and creatinine) and calf circumference were the most commonly used serum biomarkers (123 citations) and anthropometric indexes (127 citations), respectively. Ultrasound was the most commonly used imaging tool for screening sarcopenia (57 citations). The included tools varied significantly in content. Various tools assessed some or all components of sarcopenia with different methods, and others assessed different domains, such as age, body mass index, falls, diet, and even mental health. We also summarized the screening tools that were validated in different clinical settings (hospitals, communities, nursing homes, and health checkups).

CONCLUSIONS AND IMPLICATIONS

More than 50 validated tools are currently available for screening sarcopenia in different clinical settings. The results of this review may help clinicians and researchers in selecting optimal tools for sarcopenia in different clinical scenarios and in developing future tools.

Clinically Meaningful Fatigue and Depression Are Associated with Sarcopenia in Patients with Non-Alcoholic Fatty Liver Disease

BACKGROUND

Sarcopenia is thought to be related to an increased risk of non-alcoholic steatohepatitis and advanced liver fibrosis. Our cross-sectional single-center study was designed to analyze the prevalence of sarcopenia in patients with NAFLD and possible influencing factors.

METHODS

A survey on the presence of sarcopenia, fatigue, anxiety, and depression, along with a quality-of-life (QoL) assessment, was forwarded by email to 189 outpatients. Demographics, anthropometric and clinical data (laboratory test results and abdomen complete ultrasound protocol), performed within 2-4 weeks prior to the enrollment, were obtained.

RESULTS

Sarcopenia (defined as SARC-F score ≥ 4) was identified in 17 (15.7%) patients, all of them (100%) females, with median age (interquartile range) 56 (51-64) years. These patients had a poorer metabolic state (greater values of waist and hip circumferences, body mass index, and HOMA-IR) and significantly poorer QoL, specifically, regarding the physical component of health, compared with NAFLD patients without sarcopenia. Multivariate analysis showed that depression (OR = 1.25, 95% CI: 1.02-1.53, p = 0.035) and clinically meaningful fatigue (OR = 1.14, 95% CI: 1.04-1.26, p = 0.008) were the factors independently associated with sarcopenia in patients with NAFLD.

CONCLUSION

Sarcopenia is associated with depression and fatigue rather than with the severity of liver disease alone and may negatively affect QoL in patients with NAFLD.

Serum creatinine/cystatin C ratio as a muscle mass evaluating tool and prognostic indicator for hospitalized patients: A meta-analysis

Objective

Sarcopenia is a syndrome of decreased muscle mass and deficits in muscle strength and physical function. We aimed to investigate the relationship between creatinine/cystatin C ratio (CCR) and sarcopenia and the prognostic value of CCR in hospitalized patients.

Materials and methods

We searched for relevant studies in PubMed, EMBASE, and the Cochrane Database up to August 25, 2022. Meta-analyses were performed to evaluate the relationship between CCR and skeletal muscle [computed tomography-assessed skeletal muscle (CTASM), muscle strength, and physical performance], prognosis and important clinical outcomes in hospitalized adults. The pooled correlation coefficient, the area under the receiver operating characteristic (ROC) curves, and hazard ratio (HR) together with their 95% confidence intervals (CIs) were calculated. We also conducted subgroup analyses to explore the sources of heterogeneity.

Results

A total of 38 studies with 20,362 patients were eligible. These studies were of moderate to high quality. Our results showed that CCR was significant correlations with all CTASM types (Fisher's Z ranged from 0.35 to 0.5; P values ranged from < 0.01 to 0.01), handgrip strength (Fisher's Z = 0.39; 95% CI, 0.32-0.45; P < 0.001) and gait speed (Fisher's Z = 0.25; 95% CI, 0.21-0.30; P < 0.001). The ROC curves suggested that CCR had good diagnostic efficacy (0.689; 95% CI, 0.632-0.746; P < 0.01) for sarcopenia. CCR can reliably predict mortality in hospitalized patients, which was confirmed by regression analysis of CCR as both continuous (HR 0.78; 95% CI, 0.72-0.84; P < 0.01) and categorical variables (HR 2.05; 95% CI, 1.58-2.66; P < 0.0001). In addition, less evidence showed that higher CCR was independently associated with a shorter duration of mechanical ventilation, reduced length of stay in the intensive care unit and hospital, less nutritional risk, and decreased complications in hospitalized patients.

Conclusion

CCR could be a simple, economical, and effective screening tool for sarcopenia in hospitalized patients, and it is a helpful prognostic factor for mortality and other important clinical outcomes.

Systematic review registration

https://inplasy.com/inplasy-2022-9-0097/, identifier INPLASY202290097.

A New Index Based on Serum Creatinine and Cystatin C Can Predict the Risks of Sarcopenia, Falls and Fractures in Old Patients with Low Bone Mineral Density

As new screening tools for sarcopenia, the serum sarcopenia index (SI) and creatinine/cystatin C ratio (CCR) had not been confirmd in a population with a high fragility fracture risk. This study aimed to evaluate whether SI and CCR indicators are useful for diagnosing sarcopenia and to determine their prediction values for future falls and fractures. A total of 404 hospitalized older adults were enrolled in this longitudinal follow-up study (mean age = 66.43 ± 6.80 years). The receiver operating curve (ROC) was used to assess the diagnostic accuracy of SI and CCR. Backward-selection binary logistic regression was applied to develop the optimal models for the diagnosis of new falls and fractures. SI had a significantly higher area under the curve (AUC) than CCR for predicting sarcopenia. The optimal models had acceptable discriminative powers for predicting new falls and fractures. Lower SI and CCR are the independent risks for sarcopenia, new falls, and fractures in the low-BMD population. SI and CCR, as easily accessible biochemical markers, may be useful in the detection of sarcopenia and in predicting the occurrence of new falls and fractures in patients with low BMD who have not previously experienced falls or fractures. However, further external validations are required.

Sarcopenia and sarcopenic obesity in chronic kidney disease: update on prevalence, outcomes, risk factors and nutrition treatment

PURPOSE OF REVIEW

This review summarizes literature from the last 18 months reporting on sarcopenia (or its components) in chronic kidney disease (CKD).

RECENT FINDINGS

The prevalence of sarcopenia in CKD is reported to be 5-62.5%, with higher rates observed later in the disease. Sarcopenic obesity rates are reported to be 2-23%. Sarcopenia in CKD is associated with increased risk of mortality, cardiovascular disease and vascular calcification. Risk factors include kidney disease itself and the impacts of CKD on lifestyle (reduced physical activity, diet changes). In earlier stages of CKD, if the risks from sarcopenia outweigh the risk of reaching end-stage renal disease, ensuring adequate energy intake combined with modest protein liberalization and physical activity may be indicated. Protein intakes above 1.3 g/kg of body weight per day should be avoided. For dialysis patients, interventions that provide a combination of carbohydrate, protein and fat appear more effective than those that provide protein alone, though it may take as long as 48 weeks for detectable changes in muscle mass.

SUMMARY

Sarcopenia is prevalent in CKD as kidney disease significantly impacts muscle mass and function. Nutrition interventions can improve components of sarcopenia, with an emphasis on adequate energy and protein.