Assessment of Cystatin C Level for Risk Stratification in Adults With Chronic Kidney Disease

Chronic kidney disease in geriatric patients: Estimating glomerular filtration rate in older patients with comorbidities

Aging is an inevitable process that is usually measured by chronological age, with people aged 65 and over being defined as "older individuals". There is disagreement in the current scientific literature regarding the best methods to estimate glomerular filtration rate (eGFR) in older adults. Several studies suggest the use of an age-adjusted definition to improve accuracy and avoid overdiagnosis. In contrast, some researchers argue that such changes could complicate the classification of chronic kidney disease (CKD). Several formulas, including the Modification of Diet in Renal Disease, CKD-Epidemiology Collaboration, and Cockcroft-Gault equations, are used to estimate eGFR. However, each of these formulas has significant limitations when applied to older adults, primarily due to sarcopenia and malnutrition, which greatly affect both muscle mass and creatinine levels. Alternative formulas, such as the Berlin Initiative Study and the Full Age Spectrum equations, provide more accurate estimates of values for older adults by accounting for age-related physiological changes. In frail older adults, the use of cystatin C leads to better eGFR calculations to assess renal function. Accurate eGFR measurements improve the health of older patients by enabling better medication dosing. A thorough approach that includes multiple calibrated diagnostic methods and a detailed geriatric assessment is necessary for the effective management of kidney disease and other age-related conditions in older adults.

Emerging Biomarkers and Advanced Diagnostics in Chronic Kidney Disease: Early Detection Through Multi-Omics and AI

Chronic kidney disease (CKD) remains a significant global health burden, often diagnosed at advanced stages due to the limitations of traditional biomarkers such as serum creatinine and estimated glomerular filtration rate (eGFR). This review aims to critically evaluate recent advancements in novel biomarkers, multi-omics technologies, and artificial intelligence (AI)-driven diagnostic strategies, specifically addressing existing gaps in early CKD detection and personalized patient management. We specifically explore key advancements in CKD diagnostics, focusing on emerging biomarkers-including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), soluble urokinase plasminogen activator receptor (suPAR), and cystatin C-and their clinical applications. Additionally, multi-omics approaches integrating genomics, proteomics, metabolomics, and transcriptomics are reshaping disease classification and prognosis. Artificial intelligence (AI)-driven predictive models further enhance diagnostic accuracy, enabling real-time risk assessment and treatment optimization. Despite these innovations, challenges remain in biomarker standardization, large-scale validation, and integration into clinical practice. Future research should focus on refining multi-biomarker panels, improving assay standardization, and facilitating the clinical adoption of precision-driven diagnostics. By leveraging these advancements, CKD diagnostics can transition toward earlier intervention, individualized therapy, and improved patient outcomes.

Discordance between cystatin C-based and creatinine-based estimated glomerular filtration rate and health outcomes in adults: a systematic review and meta-analysis

Background

The intra-individual difference in cystatin C-based and creatinine-based estimated glomerular filtration rate (eGFRcys and eGFRcr, respectively), i.e. eGFR discordance, has recently been demonstrated to have prognostic implications. eGFR discordance was associated with mortality, cardiovascular and renal outcomes. We present a systematic review and meta-analysis to summarize the existing literature.

Methods

We searched PubMed, Embase and MEDLINE up to 28 April 2024 for cohort and cross-sectional studies in English reporting the association of eGFR discordance with mortality, cardiovascular and renal outcomes. The quality of studies was evaluated by Risk Of Bias In Non-randomized Studies-of Exposure (ROBINS-E) form. Data from studies were extracted to a pre-defined table and pooled using a random-effects model. Stratified and sensitivity analyses were performed.

Results

A total of 1489 studies were initially identified, of which 18 studies with longitudinal or cross-sectional designs were included, with a sample size between 373 and 363 494 people. In general, the risk of bias was graded as "low" or "some concerns". eGFR was mainly calculated using Chronic Kidney Disease Epidemiology Collaboration equations, while a few studies applied other equations. An eGFR discordance featuring lower eGFRcys, e.g. eGFRcys ≤60% of eGFRcr, or eGFRcys-eGFRcr ≤-15 mL/min/1.73 m2, was consistently associated with higher mortality and elevated risk of cardiovascular and renal outcomes. People with lower eGFRcys have a 58% greater risk of mortality [hazard ratio (HR) = 1.58, 95% confidence interval (CI) 1.42, 1.76] and 32% greater risk of cardiovascular events (HR = 1.32, 95% CI 1.25, 1.39). People with higher eGFRcys have a 39% lower risk of mortality (HR = 0.61, 95% CI 0.52, 0.70) and 29% lower risk of cardiovascular events (HR = 0.71, 95% CI 0.62, 0.81). No meta-analysis for renal outcomes was conducted due to data availability.

Conclusions

The eGFR discordance serves as a meaningful indicator of adverse health outcomes. The lack of a consensus on the cut-off value of eGFR discordance and the mixture use of eGFR equations warrants attention.

Outcomes of KDIGO-Defined CKD in U.S. Veterans With HFpEF, HFmrEF, and HFrEF

BACKGROUND

Chronic kidney disease (CKD) is defined by the KDIGO (Kidney Disease: Improving Global Outcomes) guideline as abnormal kidney structure or function, present for >3 months, with implications for health. KDIGO-defined CKD is associated with poor outcomes in patients with heart failure (HF). Less is known about whether these associations vary by left ventricular ejection fraction.

OBJECTIVES

This study aims to determine the prevalence and outcomes of KDIGO-defined CKD in heart failure with preserved ejection fraction (HFpEF), heart failure with mildly reduced ejection fraction (HFmrEF), and heart failure with reduced ejection fraction (HFrEF).

METHODS

Of the 1,446,053 veterans with an HF diagnosis (1991-2017) in the national Veterans Affairs electronic health record data, 365,000 with data on EF had KDIGO-defined CKD or normal kidney function (NKF). CKD was defined as 2 values measured 90 days apart of estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 (categorized into 4 eGFR stages based on the last eGFR: 45-59 mL/min/1.73 m2, 30-44 mL/min/1.73 m2, 15-29 mL/min/1.73 m2, and <15 mL/min/1.73 m2) or urinary albumin-to-creatinine ratio (uACR) >30 mg/g (albuminuria). NKF was defined as 2 values measured >90 days apart of eGFR ≥60 mL/min/1.73 m2, without eGFR <60 mL/min/1.73 m2 or albuminuria for 3 years before HF diagnosis. Patients were categorized into HFpEF (EF ≥50%, n = 85,855), HFmrEF (EF 41%-49%, n = 39,397), and HFrEF (EF ≤40%, n = 139,748). HRs and 95% CIs for 5-year all-cause mortality and HF hospitalization through December 31, 2022, associated with the 5 CKD groups (vs NKF) were estimated using Cox regression.

RESULTS

Among patients with HF and NKF, mortality occurred in 39%, 37%. and 41%, and HF hospitalization occurred in 12%, 15%, and 21% of those with HFpEF, HFmrEF. and HFrEF, respectively. Compared with NKF, CKD was associated with 16%, 19%, and 26% higher multivariable-adjusted risks for death in patients with HFpEF, HFmrEF, and HFrEF, respectively. Respective risks for HF hospitalization were 31%, 33%, and 32% higher. The eGFR-associated risks were incrementally higher with decreasing eGFR, except for eGFR <15 mL/min/1.73 m2, likely because of the initiation of dialysis during follow-up. Albuminuria was associated with 16%, 10%, and 12% higher multivariable-adjusted risks for death and 29, 30%, and 24% for HF hospitalization in HFpEF, HFmrEF, and HFrEF, respectively. All associations were statistically significant.

CONCLUSIONS

These findings based on KDIGO-defined CKD and NKF provide new information about the best estimates of true prevalence and outcomes of CKD in HFpEF, HFmrEF, and HFrEF.

The independent and interactive effects of heavy metal pollution and vitamin D deficiency on early kidney injury indicators: analysis of the National Health and Nutrition Examination Survey 2001-2004

BACKGROUND

Heavy metals (e.g., cadmium, lead, mercury, etc.) can infiltrate the human body via diverse routes, with a propensity to accumulate in the kidney cortex, thereby precipitating kidney dysfunction. Vitamin D has been implicated in mitigating the oxidative stress and inflammatory reactions triggered by heavy metal exposure. However, the interplay between heavy metal toxicity and vitamin D deficiency in the context of incipient kidney injury remains an underexplored area of research.

METHODS

Utilizing data from the National Health and Nutrition Examination Survey spanning from 2001 to 2004, Our methodology leveraged spline smoothing within the framework of generalized additive models to more vividly elucidate the impact of heavy metal exposure and serum vitamin D levels on the trajectory of early kidney injury biomarkers (including albumin-to-creatinine ratio, β-2 microglobulin (B2M), cystatin C (CYST), and estimated glomerular filtration rate (eGFR) (serum creatinine(SCr)-based(eGFR), CYST-based eGFR, and SCr-CYST-based eGFR). Furthermore, we conducted an interaction analysis to assess the combined effects of heavy metal exposure and vitamin D deficiency on early kidney injury.

RESULTS

The cohort comprised 2,422 adults. Our results indicated that cadmium levels were positively correlated with B2M, CYST, and negatively correlated with eGFRc, eGFRs. Similarly, lead levels showed a positive correlation with ACR, B2M, and CYST, and negative correlation with eGFRc, eGFRc&s. In contrast, mercury levels were negatively correlated with B2M, CYST and positively correlated with eGFRc. In addition, there was an interaction between lead exposure and vitamin D deficiency in early kidney injury indicators (P for interaction: B2M: 0.028, CYST: 0.038, eGFRc&s: 0.011).

CONCLUSIONS

This study suggests a correlation between exposure to cadmium and lead and an increased risk of early kidney injury. It highlights the potential importance of targeted vitamin D supplementation and reduction in lead exposure in mitigating early kidney injury. However, these findings warrant validation through further prospective research.

Positive Correlation Between Serum Limonene Levels and Muscle Health in a Representative Adult Population in the United States

Background/Objectives: Monoterpenes, a class of organic compounds with the molecular formula C10H16, have garnered significant attention for their potential medicinal benefits. Emerging evidence suggests they may positively influence skeletal muscle function. However, the impact of monoterpene exposure on muscle strength and mass in humans remains unclear. Methods: To explore this relationship, we analyzed data from 1202 adults (aged ≥ 18 years) who participated in the 2013-2014 National Health and Nutrition Examination Survey (NHANES), focusing on serum levels of three specific monoterpenes-α-pinene, β-pinene, and limonene-and their association with hand grip strength and lean muscle mass. Results: Our analysis revealed that, except for test 2 of hand 1, all grip strength measures showed a positive correlation with ln-limonene levels. The β coefficient for combined grip strength was 2.409 (S.E. = 0.891, p = 0.015). Positive associations were also found between serum limonene levels and lean muscle mass. The β coefficient for the Appendicular Skeletal Muscle Mass Index (ASMI) was 0.138 (S.E. = 0.041, p = 0.004). Furthermore, combined grip strength and ASMI significantly increased across limonene quintiles (p for trend = 0.005 and 0.006, respectively). However, none of the three monoterpene levels showed a significant association with clinically defined low muscle mass or low muscle strength. Conclusions: Our findings suggest a plausible association between exposure to limonene, hand grip strength, and lean muscle mass among adults in the United States. Further investigation is needed to fully understand the underlying mechanisms and medical significance of this association.

Embedding Equity and Inclusion Principles Into Nephrology Board Examinations: An Essential Part of Our Path Toward Kidney Health Justice

Recognition of widespread health inequalities across disease conditions and their startling impact on morbidity and health care costs have motivated multiple professional societies to ensure board examinations reflect and enhance inclusive, anti-biased, and equitable care. In this perspective, we offer five nephrology case examples and accompanying learning objectives to demonstrate how principles of inclusion, equity, and anti-bias can be embedded into nephrology examinations to enhance care for all populations.

2024 Latin American Society of Hypertension guidelines on the management of arterial hypertension and related comorbidities in Latin America

Hypertension is responsible for more than two million deaths due to cardiovascular disease annually in Latin America (LATAM), of which one million occurs before 70 years of age. Hypertension is the main risk factor for cardiovascular morbidity and mortality, affecting between 20 and 40% of LATAM adults. Since the publication of the 2017 LASH hypertension guidelines, reports from different LATAM countries have confirmed the burden of hypertension on cardiovascular disease events and mortality in the region. Many studies in the region have reported and emphasized the dramatically insufficient blood pressure control. The extremely low rates of awareness, treatment, and control of hypertension, particularly in patients with metabolic disorders, is a recognized severe problem in LATAM. Earlier implementation of antihypertensive interventions and management of all cardiovascular risk factors is the recognized best strategy to improve the natural history of cardiovascular disease in LATAM. The 2024 LASH guidelines have been developed by a large group of experts from internal medicine, cardiology, nephrology, endocrinology, general medicine, geriatrics, pharmacology, and epidemiology of different countries of LATAM and Europe. A careful search for novel studies on hypertension and related diseases in LATAM, together with the new evidence that emerged since the 2017 LASH guidelines, support all statements and recommendations. This update aims to provide clear, concise, accessible, and useful recommendations for health professionals to improve awareness, treatment, and control of hypertension and associated cardiovascular risk factors in the region.

Sanqi oral solution ameliorates renal fibrosis by suppressing fibroblast activation via HIF-1α/PKM2/glycolysis pathway in chronic kidney disease

ETHNOPHARMACOLOGICAL RELEVANCE

Sanqi oral solution (SQ) is a traditional Chinese patent medicine, widely used to treat chronic kidney diseases (CKD) in the clinic in China. Previous studies have confirmed its anti-renal fibrosis effect, but the specific pharmacological mechanism is still unclear.

AIM OF THE STUDY

Focusing on energy metabolism in fibroblasts, the renoprotective mechanism of SQ was investigated in vitro and in vivo.

METHODS

Firstly, the fingerprint of SQ was constructed and its elementary chemical composition was analyzed. In the 5/6Nx rats experiment, the efficacy of SQ on the kidney was evaluated by detecting serum and urine biochemical indexes and pathological staining of renal tissues. Lactic acid and pyruvic acid levels in serum and renal tissues were detected. PCNA protein expression in kidney tissue was detected by immunofluorescence assay and Western blot. Expression levels of HIF-1α, PKM2 and HK2 were determined by immunohistochemistry, Western blot or RT-qPCR assay. In addition, the effect of SQ intervention on cell proliferation and glycolysis was evaluated in TGF-β1-induced NRK-49F cells, and the role of SQ exposure and HIF-1α/PKM2/glycolysis pathway were further investigated by silencing and overexpressing HIF-1α gene in NRK-49F cells.

RESULTS

In 5/6 Nx rats, SQ effectively improved renal function and treated renal injury. It reduced the levels of lactic acid and pyruvic acid in kidney homogenates from CKD rats and decreased the expression levels of HIF-1α, PKM2, HK2, α-SMA, vimentin, collagen I and PCNA in kidney tissues. Similar results were observed in vitro. SQ inhibited NRK-49F cell proliferation, glycolysis and the expression levels of HIF-1α, PKM2 induced by TGF-β1. Furthermore, we established NRK-49F cells transfected with siRNA or pDNA to silence or overexpress the HIF-1α gene. Overexpression of HIF-1α promoted cellular secretion of lactic acid and pyruvic acid in TGF-β1-induced NRK-49F cells, however, this change was reversed by intervention with SQ or silencing the HIF-1α gene. Overexpression of HIF-1α can further induce increased PKM2 expression, while SQ intervention can reduce PKM2 expression. Moreover, PKM2 expression was also inhibited after silencing HIF-1α gene, and SQ was not effective even when given.

CONCLUSION

The mechanism of action of SQ was explored from the perspective of energy metabolism, and it was found to regulate PKM2-activated glycolysis, inhibit fibroblast activation, and further ameliorate renal fibrosis in CKD by targeting HIF-1α.

The relationship between dietary inflammatory index (DII) and early renal injury in population with/without hypertension: analysis of the National health and nutrition examination survey 2001-2002

BACKGROUND

Inflammation plays a crucial role in occurrence of kidney injury, and specific dietary patterns can influence systemic inflammation levels. However, the relationship between dietary inflammatory potential and early-stage kidney damage remains unclear.

METHOD

2,108 participants was recruited from 2001-2002 National Health and Nutrition Examination Survey (NHANES). Dietary Inflammatory Index (DII) is utilized to assess dietary inflammatory potential, calculated through a 24-h dietary recall questionnaire. Early renal injury was evaluated using urinary albumin to creatinine (UACR), cystatin C (CysC), β-2 microglobulin (β2M), and estimated glomerular filtration rate (eGFR) based on serum creatinine (eGFRs), cystatin C (eGFRc), and both Scr and CysC (eGFRs&c). Participant characteristics were analyzed, and association between DII, hypertension, and early renal injury markers was explored using multiple linear and logistic regression models.

RESULTS

The average age of participants was 53.9 years. DII exhibited a positive correlation with UACR (β = -0.048[0.017,0.078]), β2M (β = 0.019[0.010,0.027]), CysC (β = 0.012 [0.004,0.021]). Conversely, a negative correlation was observed between DII and eGFRc (β = -1.126[-1.554, -0.699]), eGFRs&c (β=-1.101[-1.653, -0.549]). A significant association was observed between hypertension and abnormality of early kidney damage markers. Subgroup analysis reveals that the positive correlation between DII and the occurrence of abnormal markers of early kidney damage is only observed in individuals with hypertension. Furthermore, an interaction between DII and hypertension was detected in eGFRs&c (OR:1.250[1.042, 1.499], p for interaction = 0.03).

CONCLUSION

Higher levels of DII may be associated with occurrence of early kidney damage. For individuals with hypertension, avoiding excessive consumption of pro-inflammatory foods may reduce the risk of renal injury.

The Impact of the Natural Level of Blood Biochemicals on Electroencephalographic Markers in Healthy People

This study aims to investigate the association between the natural level of blood biomarkers and electroencephalographic (EEG) markers. Resting EEG theta, alpha (ABP), beta, and gamma frequency band powers were selected as linear EEG markers indicating the level of EEG power, and Higuchi's fractal dimension (HFD) as a nonlinear EEG complexity marker reflecting brain temporal dynamics. The impact of seven different blood biomarkers, i.e., glucose, protein, lipoprotein, HDL, LDL, C-reactive protein, and cystatin C, was investigated. The study was performed on a group of 52 healthy participants. The results of the current study show that one linear EEG marker, ABP, is correlated with protein. The nonlinear EEG marker (HFD) is correlated with protein, lipoprotein, C-reactive protein, and cystatin C. A positive correlation with linear EEG power markers and a negative correlation with the nonlinear complexity marker dominate in all brain areas. The results demonstrate that EEG complexity is more sensitive to the natural level of blood biomarkers than the level of EEG power. The reported novel findings demonstrate that the EEG markers of healthy people are influenced by the natural levels of their blood biomarkers related to their everyday dietary habits. This knowledge is useful in the interpretation of EEG signals and contributes to obtaining information about people quality of life and well-being.

Comprehensive comparative evaluation of the eight pediatric estimated glomerular filtration rate equations in a large Korean pediatric patient cohort

Introduction

Although estimated glomerular filtration rate (eGFR) are continuously developed for pediatric population, impact of height measurement is often neglected due to variable dynamic growth changes in children. This study aimed to compare differential impacts of eGFR values calculated by six equations that do not use height information.

Materials and methods

3503 Korean pediatric patients with creatinine/cystatin C assay-based laboratory results from 2008 to 2021 were analyzed for clinical course using a total of 8113 laboratory test results. Baseline eGFR was calculated by eight different equations including two widely used equations incorporating height parameter. Along with the agreement of CKD (chronic kidney disease) stage categorization by different equations, clinical outcome of incident CKD diagnosis in 13 years of study period were compared.

Results

Among a total of 28 pairwise comparisons among eight equations, only 4 combinations of comparisons revealed optimal P15 values (≥80 % concordance), with FAS-age equation being both concordant with two equations using height parameter. Clustering of eight equations by incident CKD diagnosis in subsequent tests also highlighted FAS-age as candidate equation within the same cluster with Schwartz-bedside and FAS-height equations. When the equation values were classified into Kidney Disease Improving Global Outcomes (KDIGO) CKD stages, the distribution patterns for stage 1 and 5 were significantly different among eGFR equations. FAS-age equation revealed the highest agreement with Schwartz-bedside and FAS-height equations that incorporate the height data.

Conclusions

The eGFR equation type should be considered to establish the eGFR intervals for CKD stage classification, particularly in the pediatric patient population. Cautious interpretation is required for eGFR value along with clinical context.

Chronic Kidney Disease-Part 1: Evaluation & Risk Assessment in CKD, Methods to Delay CKD Progression

Chronic kidney disease (CKD) is common and leads to significant morbidity and mortality. Early detection and deployment of effective therapies could prevent CKD progression and related cardiovascular diseases. This review provides a case-based overview of key issues surrounding the diagnosis, staging, and management of CKD.

Detecting and managing the patient with chronic kidney disease in primary care: A review of the latest guidelines

Chronic kidney disease (CKD) is a major global health problem, affecting about 9.5% of the population and 850 million people worldwide. In primary care, most CKD is caused by diabetes and/or hypertension, but a substantial proportion of cases may have alternative causes. During the early stages, CKD is asymptomatic, and many people are unaware that they are living with the disease. Despite the lack of symptoms, CKD is associated with elevated risks of cardiovascular disease, progressive kidney disease, kidney failure and premature mortality. Risk reduction strategies are effective and cost-effective but require early diagnosis through testing of the estimated glomerular filtration rate and albuminuria in high-risk populations. Once diagnosed, the treatment of CKD centres around lifestyle interventions, blood pressure and glycaemic control, and preventative treatments for cardiovascular disease and kidney disease progression. Most patients with CKD should be managed with statins, renin-angiotensin-aldosterone system inhibitors and sodium-glucose cotransporter-2 inhibitors. Additional treatment options to reduce cardiorenal risk are available in patients with diabetes, including glucagon-like peptide-1 receptor agonists and non-steroidal mineralocorticoid receptor antagonists. The Kidney Failure Risk Equation is a new tool that can support the identification of patients at high risk of progressive kidney disease and kidney failure and can be used to guide referrals to nephrology. This review summarizes the latest guidance relevant to managing adults with, or at risk of, CKD and provides practical advice for managing patients with CKD in primary care.

What every clinician needs to know about chronic kidney disease: Detection, classification and epidemiology

Chronic kidney disease (CKD) is a major healthcare challenge, affecting >800 million people worldwide. Implications for population health result from the strong associations of CKD with increased rates of cardiovascular disease, heart failure, progressive CKD leading to kidney failure, acute kidney injury (AKI), and mortality. In addition to a single disease perspective, CKD commonly coexists alongside other long-term conditions, in particular type 2 diabetes and cardiovascular disease. CKD is therefore an important component of multimorbidity that influences individual management and impacts prognosis. CKD is defined by abnormalities of kidney structure or function of any cause with implications for health that are present for longer than 3 months. The diagnosis is usually made on the basis of an abnormal glomerular filtration rate (GFR < 60 mL/min/1.73 m2) and/or the presence of proteinuria (urine albumin to creatinine ratio > 30 mg/g or >3 mg/mmol). GFR is usually estimated from serum creatinine concentration using a variety of validated equations. However, serum creatinine is closely related to muscle mass and may therefore not be an accurate marker of GFR in people with high or low muscle mass (sarcopaenia). Cystatin C is an alternative endogenous marker of GFR that is increasingly being used but also has limitations. An estimate of GFR based on both creatinine and cystatin C is the most accurate. Diagnosis should be followed by classification and risk stratification to guide the development of a risk-based, personalized care plan. Improved detection and widespread implementation of optimal CKD management has the potential to bring major benefits to population health.

Prediction of cardiovascular events and all-cause mortality using race and race-free estimated glomerular filtration rate in African Americans: the Jackson Heart Study

Background

New Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations without a race adjustment were developed to estimate the glomerular filtration rate (eGFR). We aimed to compare the performance of five CKD-EPI eGFR equations, with or without race, in predicting cardiovascular disease (CVD) events and all-cause mortality in Black Americans from the Jackson Heart Study.

Methods

JHS is an ongoing population-based prospective cohort study of African Americans in the Jackson, Mississippi, metropolitan area. Five CKD-EPI equations were used to estimate GFR at baseline using serum creatinine (Cr) or cystatin C (cys), including 2009 eGFRcr(ASR [age, sex, race]), 2021 eGFRcr(AS [age and sex]), 2012 eGFRcr-cys(ASR), 2021 eGFRcr-cys(AS), 2012 eGFRcys(AS). Endpoints were incident CVD events and all-cause mortality. Cox proportional hazards regression was used to assess the associations between different eGFRs and outcomes adjusting for atherosclerotic risk factors. Harrell's C-statistics and Net Reclassification Index (NRI) were used to assess the predictive utility.

Results

Among 5,129 participants (average age 54.8 ± 12.8 yrs), 1898 were male (37.0%). eGFRcr(AS) provided lower estimates and resulting in a greater proportion of participants categorized as CKD than eGFRcr(ASR), eGFRcr-cys(ASR), eGFRcr-cys(AS) and eGFRcys(AS). A median follow-up of 13.7 and 14.3 years revealed 411 (9.3%) CVD incidents and 1,207 (23.5%) deaths. Lower eGFRs were associated with CVD incidents and all-cause mortality. eGFRcr-cys(ASR), eGFRcr-cys(AS) and eGFRcys(AS) were strongly associated with incident CVD events and all-cause mortality than eGFRcr(ASR) and eGFRcr(AS). A significant discrimination improvement was found in C-statistics for predicting incident CVD events and all-cause mortality after adding each eGFR measure to the basic model including atherosclerotic risk factors. Across a 7.5% 10-year risk threshold, eGFRcys(AS) improved net classification of all-cause mortality (NRI: 2.19, 95%CI: 0.08, 4.65%).

Conclusion

eGFR based on creatinine omit race has the lowest mean and detects more CKD patients in Black population. The eGFRs incorporating cystatin C strengthens the association between the eGFR and the risks of incident CVD and all-cause mortality. Cystatin C-based eGFR equations might be more appropriate for predicting CVD and mortality among Black population.

CKD Prevalence and Incidence in Older Adults Using Estimated GFR With Different Filtration Markers: The Atherosclerosis Risk in Communities Study

Rationale & Objective

The prevalence of chronic kidney disease (CKD) is known to increase with age; however, creatinine may be a less reliable filtration marker in older adults. Few studies have investigated the prevalence and progression of CKD using different filtration markers for estimating glomerular filtration rate (GFR).

Study Design

A prospective observational cohort study.

Setting & Participants

6,393 White and African American participants aged 65-100 years from the Atherosclerosis Risk in Communities Study (ARIC) at Visit 5, followed longitudinally at Visits 6 and 7.

Exposure and Outcome

The eGFR was estimated either by creatinine (eGFRcr), cystatin C (eGFRcys), creatinine and cystatin C (eGFRcr-cys), or using creatinine, cystatin C, and β-2-microglobulin (eGFRcr-cys-b2m). CKD progression was defined as 30% decline in eGFR at follow-up visits.

Analytical Approach

Logistic regression models, adjusted for sex, race and study center, diabetes, blood pressure, body mass index, prevalent cardiovascular disease, and heart failure.

Results

At Visit 5, the mean age in the study population was 75.8 years, and the mean eGFR ranged from 71.2 to 61.2 mL/min/1.73m2 using eGFRcr or eGFRcys, respectively. The proportion with eGFR < 60 mL/min/1.73m2 was lowest with eGFRcr and highest with eGFRcys for all age groups, and prevalence increased with age for all markers. For example, the prevalence of eGFRcr < 60 mL/min/1.73m2 in ages 70-74 years ranged from 15% to 21% and in ages 85-89 years ranged from 38% to 46% at the different visits. The proportion with a 30% eGFR decline over a mean of 8 years in people who were originally aged 65-69 years ranged from 9% (eGFRcr)-18% (eGFRcys). More people with eGFRcr ≥ 60 mL/min/1.73m2 were reclassified to < 60 mL/min/1.73m2 when using eGFRcys (33%) compared with eGFRcr-cys (12%) or eGFRcr-cys-b2m (18%). The proportion with 30% eGFR decline was lowest with eGFRcr and highest with eGFRcys, with greater incidence in older age groups for all markers.

Limitations

No direct measurement of GFR. Not all participants survived or attended subsequent follow-up visits.

Conclusions

The prevalence and progression of CKD increase with age, but estimates vary with the filtration marker used. The eGFRcr gave the lowest estimate of CKD at 15% for people aged 65-69 years at Visit 5 while eGFRcys gave the highest estimates of CKD at 26% for that same population.

Joint effects of sleep disturbance and renal function impairment on incident new-onset severe metabolic dysfunction-associated steatotic liver disease

AIM

To elucidate the effects of sleep parameters and renal function on the risk of developing new-onset severe metabolic dysfunction-associated steatotic liver disease (MASLD).

MATERIALS AND METHODS

The primary analysis involved a cohort of 305 257 participants. Multivariable Cox models were employed to calculate hazard ratios and 95% confidence intervals. Traditional mediation and two-step Mendelian randomization (MR) analyses were conducted to assess the associations and mediating roles of renal function indicators between sleep and new-onset severe MASLD.

RESULTS

Poor sleep score and renal function biomarker score (RFS) were associated with an increased risk of new-onset severe MASLD (all ptrend <0.001). Participants with poor sleep patterns and the highest RFS had a 5.45-fold higher risk of new-onset severe MASLD, compared to those with healthy sleep patterns and the lowest RFS (p < 0.001). The RFS could explain 10.08% of the correlations between poor sleep score and risk of new-onset severe MASLD. Additionally, MR analyses supported a causal link between insomnia and new-onset severe MASLD and revealed a mediating role of chronic kidney disease in the connection between insomnia and new-onset severe MASLD risk.

CONCLUSIONS

This study highlights the independent and combined associations of sleep parameters and renal function indicators with new-onset severe MASLD, underscoring the bidirectional communication of the liver-kidney axis and providing modifiable strategies for preventing MASLD.

Cystatin C vs creatinine eGFR in advanced CKD: an analysis of the STOP-ACEi trial

Background

In this secondary analysis of the STOP-ACEi trial, we explored the impact of discontinuing or continuing renin-angiotensin system inhibitor therapy in people with advanced chronic kidney disease on cystatin C estimated glomerular filtration rate (eGFR).

Methods

Cystatin C eGFRs were calculated at baseline, 12, 24 and 36 months using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) cystatin 2012, European Kidney Function Consortium and CKD-EPI Combined 2021 equations. We excluded samples obtained after the initiation of kidney replacement therapy. Primary analysis used complete case analysis and mixed-effects linear regression model, adjusting for minimization variables, baseline value, time-point and treatment by time interaction. Sensitivity analysis was conducted using a pattern mixture model to account for missing data that was not at random. To model the longitudinal cystatin C data with time-to-event data, a joint model was utilized which incorporated the cystatin C measurements at various time points and accounted for the occurrence of kidney replacement therapy.

Results

The mean cystatin C eGFRs (CKD-EPI 2012) at baseline were 17.8 mg/L [standard deviation (SD 6.3)] and 17.9 mL/min/1.73 m2 (SD 6.3) in the STOP and CONTINUE arms, respectively. The estimated least squares mean difference at 12 months between STOP and CONTINUE arm was -1.46 [95% confidence interval (CI) -2.39 to -0.52, P = .002]. The estimated least squares mean difference at 24 months was -2.27 (95% CI -3.48 to -1.06, P < .001). The estimated least squares mean difference at 36 months was -1.72 (95% CI -3.48 to 0.03, P = .05).

Conclusion

Our results are consistent with the primary study's analysis and sensitivity analyses support these findings and provide additional insights. Our findings demonstrate the similarity of creatinine and cystatin eGFR results and therefore support the use of cystatin C as an alternative marker of eGFR in advanced CKD, particularly in those in whom creatinine is likely to be less accurate.

Endogenous adenine is a potential driver of the cardiovascular-kidney-metabolic syndrome

Mechanisms underlying the cardiovascular-kidney-metabolic (CKM) syndrome are unknown, although key small molecule metabolites may be involved. Bulk and spatial metabolomics identified adenine to be upregulated and specifically enriched in coronary blood vessels in hearts from patients with diabetes and left ventricular hypertrophy. Single nucleus gene expression studies revealed that endothelial methylthioadenosine phosphorylase (MTAP) was increased in human hearts with hypertrophic cardiomyopathy. The urine adenine/creatinine ratio in patients was predictive of incident heart failure with preserved ejection fraction. Heart adenine and MTAP gene expression was increased in a 2-hit mouse model of hypertrophic heart disease and in a model of diastolic dysfunction with diabetes. Inhibition of MTAP blocked adenine accumulation in the heart, restored heart dysfunction in mice with type 2 diabetes and prevented ischemic heart damage in a rat model of myocardial infarction. Mechanistically, adenine-induced impaired mitophagy was reversed by reduction of mTOR. These studies indicate that endogenous adenine is in a causal pathway for heart failure and ischemic heart disease in the context of CKM syndrome.

Gut microbiota dynamics and association with chronic kidney disease: A longitudinal study within the PREDIMED-Plus trial

AIMS

Chronic kidney disease (CKD) represents a global health concern, disproportionately affecting the elderly with heightened cardiovascular risk. The emerging focus on the gut microbiota's role in CKD pathophysiology represents a pivotal area in nephrology; however, the evidence on this topic is limited. This observational prospective study, in the framework of the PREDIMED-Plus trial, investigates associations between gut microbiota composition and the 1-year trajectory of CKD in 343 participants aged 55-75 years with high cardiovascular risk.

MATERIALS AND METHODS

Kidney function was assessed at baseline and at 1-year of follow-up through the estimated glomerular filtration rate based on cystatin C (eGFR-CysC) and CKD defined by eGFR-CysC <60 mL/min/1.73 m2. Participants were grouped based on their 1-year CKD trajectory: Group 1 maintained normal status or improved from CKD to normal, while Group 2 maintained CKD or worsened from normal to CKD. Fecal microbiota composition was assessed through 16S sequencing.

KEY FINDINGS

We observed differences in gut microbiota composition between CKD trajectory groups. Notably, the baseline relative abundance of Lachnoclostridium and Lachnospira, both butyrate-producing genera, was lower in participants maintaining or progressing to CKD. Longitudinally, a decrease in Lachnospira abundance was associated with CKD progression. The improved Chao1 index after 1-year follow-up suggests a link between enhanced microbial richness and stable/better kidney function.

SIGNIFICANCE

The findings underscore the potential of gut microbiota analysis in non-invasively monitoring CKD, especially in older populations, and hint at future interventions targeting gut microbiota to manage CKD progression. Further research is needed for causal relationships and generalizability.

Integrating multiple kidney function markers to predict all-cause and cardiovascular disease mortality: prospective analysis of 366 758 UK Biobank participants

Background

Reduced kidney function is a risk factor of cardiovascular and all-cause mortality. This association was demonstrated for several kidney function markers, but it is unclear whether integrating multiple measured markers may improve mortality risk prediction.

Methods

We conducted an exploratory factor analysis (EFA) of serum creatinine- and cystatin C-based estimated glomerular filtration rate [eGFRcre and eGFRcys; derived by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and European Kidney Function Consortium (EKFC) equations], blood urea nitrogen (BUN), uric acid and serum albumin among 366 758 participants in the UK Biobank without a history of kidney failure. Fitting Cox proportional hazards models, we compared the ability of the identified latent factors to predict overall mortality and mortality by cardiovascular disease (CVD), also considering CVD-specific causes like coronary heart disease (CHD) and cerebrovascular disease.

Results

During 12.5 years of follow-up, 26 327 participants died from any cause, 5376 died from CVD, 2908 died from CHD and 1116 died from cerebrovascular disease. We identified two latent factors, EFA1 and EFA2, both representing kidney function variations. When using the CKD-EPI equation, EFA1 performed like eGFRcys, with EFA1 showing slightly larger hazard ratios for overall and CVD-related mortality. At 10 years of follow-up, EFA1 and eGFRcys showed moderate discrimination performance for CVD-related mortality, outperforming all other kidney indices. eGFRcre was the least predictive marker across all outcomes. When using the EKFC equation, eGFRcys performed better than EFA1 while all other results remaining similar.

Conclusions

While EFA is an attractive approach to capture the complex effects of kidney function, eGFRcys remains the most practical and effective measurement for all-cause and CVD mortality risk prediction.

Serum cystatin C, monocyte/high-density lipoprotein-C ratio, and uric acid for the diagnosis of coronary heart disease and heart failure

BACKGROUND

Coronary heart disease (CHD) and heart failure (HF) are the major causes of morbidity and mortality worldwide. Early and accurate diagnoses of CHD and HF are essential for optimal management and prognosis. However, conventional diagnostic methods such as electrocardiography, echocardiography, and cardiac biomarkers have certain limitations, such as low sensitivity, specificity, availability, and cost-effectiveness. Therefore, there is a need for simple, noninvasive, and reliable biomarkers to diagnose CHD and HF.

AIM

To investigate serum cystatin C (Cys-C), monocyte/high-density lipoprotein cholesterol ratio (MHR), and uric acid (UA) diagnostic values for CHD and HF.

METHODS

We enrolled 80 patients with suspected CHD or HF who were admitted to our hospital between July 2022 and July 2023. The patients were divided into CHD (n = 20), HF (n = 20), CHD + HF (n = 20), and control groups (n = 20). The serum levels of Cys-C, MHR, and UA were measured using immunonephelometry and an enzymatic method, respectively, and the diagnostic values for CHD and HF were evaluated using receiver operating characteristic (ROC) curve analysis.

RESULTS

Serum levels of Cys-C, MHR, and UA were significantly higher in the CHD, HF, and CHD + HF groups than those in the control group. The serum levels of Cys-C, MHR, and UA were significantly higher in the CHD + HF group than those in the CHD or HF group. The ROC curve analysis showed that serum Cys-C, MHR, and UA had good diagnostic performance for CHD and HF, with areas under the curve ranging from 0.78 to 0.93. The optimal cutoff values of serum Cys-C, MHR, and UA for diagnosing CHD, HF, and CHD+HF were 1.2 mg/L, 0.9 × 109, and 389 µmol/L; 1.4 mg/L, 1.0 × 109, and 449 µmol/L; and 1.6 mg/L, 1.1 × 109, and 508 µmol/L, respectively.

CONCLUSION

Serum Cys-C, MHR, and UA are useful biomarkers for diagnosing CHD and HF, and CHD+HF. These can provide information for decision-making and risk stratification in patients with CHD and HF.

Cystatin C should be routinely available for estimating kidney function

PURPOSE OF REVIEW

In this report, we summarize why the availability of cystatin C is important across a variety of clinical scenarios, the recent literature on when, why and in whom cystatin C testing should be considered, and how nephrologists can take practical steps to incorporate cystatin C testing into their practice.

RECENT FINDINGS

Large intra-individual discrepancies between estimated glomerular filtration rate by creatinine (eGFRcr) and estimated glomerular filtration rate by creatinine eGFRcys (known as eGFRdiff) are observed in at least 1 in 4 people. These differences are seen more commonly among more vulnerable individuals: older adults, females, non-White individuals and those living with multiple medical conditions. A large eGFRdiff, where eGFRcys is lower than eGFRcr, is associated with a plethora of adverse outcomes, including medication-associated adverse events, acute kidney injury, cardiovascular disease, kidney failure and all-cause mortality. Among studies that have measured GFR, eGFRcr-cys usually provides the most accurate estimation of kidney function compared to mGFR, including among participants with large discrepancies between eGFRcr and eGFRcys.

SUMMARY

Cystatin C improves sensitivity and specificity of chronic kidney disease diagnosis, improves detection of harmful acute and chronic changes in kidney function, improves precision of treatment eligibility and safety, and may reduce healthcare inequalities. Better education, curiosity, and motivation among nephrologists could substantially improve the availability and utilization of cystatin C.

Editorial: The evolution of glomerular filtration rate estimation: Embracing the new EKFC equation

Addressing the accurate staging of chronic kidney disease (CKD) represents a formidable challenge worldwide, resonating deeply within Ukraine's healthcare landscape. The intricacies of estimating CKD stages often result in the dilemma of its under- or overestimation, magnifying the urgency for precise assessment methods [1, 2]. The estimation of glomerular filtration rate (GFR) is a cornerstone in the assessment of kidney function, guiding diagnosis, management, and therapeutic decisions in patients with kidney disease. Traditional approaches, such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, though widely utilized, grapple with inherent limitations, potentially compromising diagnostic accuracy [3]. To confront this critical issue, the European Kidney Function Consortium (EKFC) has introduced new equations for GFR estimation using both creatinine and cystatin C, which promise to enhance the precision and applicability of kidney function assessment. Moreover, a recent KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease has recommended using the combination of creatinine and cystatin C (creatinine and cystatin C–based estimated glomerular filtration rate [eGFRcr-cys]) for assessment GFR category (1B) [4]. However, the successful integration of the EKFC equation into clinical practice necessitates widespread awareness and adoption among healthcare professionals. This editorial aims to introduce the Ukrainian nephrology community, as well as a broad readership of the journal, to this innovative approach to kidney health assessment. The limitations of creatinine-based GFR estimation. Serum creatinine, a byproduct of muscle metabolism, has been the backbone of GFR estimation for decades. However, its utility is marred by significant limitations. Creatinine production varies with muscle mass, diet, and other physiological processes, leading to inaccuracies in GFR estimation, especially in individuals with atypical body compositions or dietary habits [5, 6]. Creatinine-based GFR estimation can also be less accurate in specific populations, such as the elderly, individuals with extreme body compositions, and those with acute kidney injury [3]. In these cases, the equations may not accurately reflect kidney function, leading to potential misclassification of CKD stages. Moreover, creatinine clearance exceeds GFR because creatinine is not only filtered by the glomeruli but also secreted by the proximal tubule. This can lead to an overestimation of GFR. Conversely, in conditions where muscle mass is reduced, such as in elderly or malnourished individuals, GFR may be underestimated [3, 5]. Lastly, some medications can inhibit tubular secretion of creatinine, thereby increasing serum creatinine levels without a corresponding decrease in GFR, leading to an overestimation of CKD severity [7]. The role of cystatin C in enhancing GFR estimation. Cystatin C, a low molecular weight protein produced at a constant rate by all nucleated cells, offers a promising alternative or complementary biomarker for GFR estimation [8]. One of the key advantages of cystatin C is its independence from muscle mass, making it particularly valuable in populations where muscle mass may vary significantly, such as the elderly, individuals with malnutrition, or those with muscle wasting conditions [9]. This independence from muscle mass confers cystatin C with greater accuracy in estimating GFR, especially in patients with early-stage kidney disease where changes in muscle mass may not yet significantly affect creatinine levels [8, 9].  Studies have demonstrated that cystatin C has a higher diagnostic sensitivity for abnormal GFR compared to creatinine [10]. This means that cystatin C is more likely to identify patients with reduced kidney function. Introducing the EKFC equation. The EKFC has developed a new equation that incorporates both serum creatinine and cystatin C levels, aiming to overcome the limitations of previous formulas. This innovative approach is grounded in extensive research and validation across various populations [11–13]. The EKFC equation is race- and sex-free, addressing ethical concerns associated with previous equations and promoting a more inclusive and equitable assessment of kidney function. By combining both markers, the EKFC equation offers a more reliable estimate of GFR, particularly in individuals where discrepancies between creatinine-based and cystatin C-based estimates exist. This approach aligns with the principles of personalized medicine, emphasizing tailored healthcare interventions based on individual patient characteristics. However, the successful integration of the EKFC equation into clinical practice requires widespread awareness and adoption among healthcare professionals. To facilitate this, the EKFC has made a calculator available online at ekfccalculator.pages.dev, and there are ongoing efforts to develop additional tools to improve the implementation of these equations. These tools are crucial for enabling healthcare providers to easily apply the EKFC equation in their clinical practice, ensuring that patients benefit from the most accurate and equitable assessment of kidney function available. In conclusion, the development of the EKFC equation marks a pivotal moment in the evolution of GFR estimation. As the medical community continues to embrace the EKFC equation, it is crucial to familiarize healthcare providers with its application and implications. We sincerely believe that the evidence, as outlined above, and this editorial support the widespread adoption of the EKFC eGFR equations in Ukraine.

Association between urinary glyphosate levels and hand grip strength in a representative sample of US adults: NHANES 2013-2014

Introduction

Glyphosate, a widely utilized herbicide globally, has been linked to various health issues, including cancer, birth abnormalities, and reproductive issues. Additionally, there is growing experimental support indicating potential harm to skeletal muscles. Despite this, the impact of glyphosate on human muscle health remains unclear.

Methods

We examined information gathered from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), which included 1466 adults aged 18 or older. Our primary aim was to investigate the relationship between glyphosate exposure and hand grip strength, as well as its influence on lean muscle mass.

Results and discussion

Our investigation uncovered a detrimental correlation between glyphosate exposure and all measures of grip strength, except for the second test of the first hand. Specifically, we observed a statistically significant adverse association between glyphosate exposure and combined grip strength, which is calculated as the sum of the highest readings from both hands (ß coefficient of -2.000, S.E. = 0.891, p = 0.040). We did not observe a significant correlation between glyphosate levels, lean muscle mass, and the likelihood of reaching maximum grip strength meeting sarcopenia criteria. Additionally, we observed an interaction between age and glyphosate, as well as between body mass index (BMI) and glyphosate, concerning the association with combined grip strength. In this comprehensive analysis of NHANES data, our study reveals a potential association between glyphosate exposure and hand grip strength in the adult population. Our findings suggest the need for deeper exploration into the health effects of glyphosate exposure and its impact on muscle strength, shedding light on possible public health concerns.

Optimizing Care Delivery in Patients with Chronic Kidney Disease in the United States: Proceedings of a Multidisciplinary Roundtable Discussion and Literature Review

BACKGROUND

Approximately 37 million individuals in the United States (US) have chronic kidney disease (CKD). Patients with CKD have a substantial morbidity and mortality, which contributes to a huge economic burden to the healthcare system. A limited number of clinical pathways or defined workflows exist for CKD care delivery in the US, primarily due to a lower prioritization of CKD care within health systems compared with other areas (e.g., cardiovascular disease [CVD], cancer screening). CKD is a public health crisis and by the year 2040, CKD will become the fifth leading cause of years of life lost. It is therefore critical to address these challenges to improve outcomes in patients with CKD.

METHODS

The CKD Leaders Network conducted a virtual, 3 h, multidisciplinary roundtable discussion with eight subject-matter experts to better understand key factors impacting CKD care delivery and barriers across the US. A premeeting survey identified topics for discussion covering the screening, diagnosis, risk stratification, and management of CKD across the care continuum. Findings from this roundtable are summarized and presented herein.

RESULTS

Universal challenges exist across health systems, including a lack of awareness amongst providers and patients, constrained care team bandwidth, inadequate financial incentives for early CKD identification, non-standardized diagnostic classification and triage processes, and non-centralized patient information. Proposed solutions include highlighting immediate and long-term financial implications linked with failure to identify and address at-risk individuals, identifying and managing early-stage CKD, enhancing efforts to support guideline-based education for providers and patients, and capitalizing on next-generation solutions.

CONCLUSIONS

Payers and other industry stakeholders have opportunities to contribute to optimal CKD care delivery. Beyond addressing the inadequacies that currently exist, actionable tactics can be implemented into clinical practice to improve clinical outcomes in patients at risk for or diagnosed with CKD in the US.

Diagnosis of cardiovascular disease in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) are at high risk of cardiovascular disease (CVD) and cardiovascular death. Identifying and monitoring cardiovascular complications and hypertension is important for managing patients with CKD or kidney failure and transplant recipients. Biomarkers of myocardial ischaemia, such as troponins and electrocardiography (ECG), have limited utility for diagnosing cardiac ischaemia in patients with advanced CKD. Dobutamine stress echocardiography, myocardial perfusion scintigraphy and dipyridamole stress testing can be used to detect coronary disease in these patients. Left ventricular hypertrophy and left ventricular dysfunction can be detected and monitored using various techniques with differing complexity and cost, including ECG, echocardiography, nuclear magnetic resonance, CT and myocardial scintigraphy. Atrial fibrillation and other major arrhythmias are common in all stages of CKD, and ambulatory heart rhythm monitoring enables precise time profiling of these disorders. Screening for cerebrovascular disease is only indicated in asymptomatic patients with autosomal dominant polycystic kidney disease. Standardized blood pressure is recommended for hypertension diagnosis and treatment monitoring and can be complemented by ambulatory blood pressure monitoring. Judicious use of these diagnostic techniques may assist clinicians in detecting the whole range of cardiovascular alterations in patients with CKD and enable timely treatment of CVD in this high-risk population.

Sex differences in associations between creatinine and cystatin C-based kidney function measures with stroke and major bleeding

PURPOSE

We sought to explore whether adding kidney function biomarkers based on creatinine (eGFRCr), cystatin C (eGFRCys) or a combination of the two (eGFRCr-Cys) could improve risk stratification for stroke and major bleeding, and whether there were sex differences in any additive value of kidney function biomarkers.

METHOD

We included participants from the UK Biobank who had not had a previous ischaemic or haemorrhagic stroke or major bleeding episode, and who had kidney function measures available at baseline. Cause-specific Cox proportional hazards models tested associations between eGFRCr, eGFRCys and eGFRCr-Cys (mL/min/1.73 m2) with ischaemic and haemorrhagic stroke, major bleeding (gastrointestinal or intracranial, including haemorrhagic stroke) and all-cause mortality.

FINDINGS

Among 452,879 eligible participants, 246,244 (54.4%) were women. Over 11.5 (IQR 10.8-12.2) years, there were 3706 ischaemic strokes, 795 haemorrhagic strokes, 26,025 major bleeding events and 28,851 deaths. eGFRCys was more strongly associated with ischaemic stroke than eGFRCr: an effect that was more pronounced in women (men - HR: 1.16, 95% CI: 1.12-1.19; female to male comparison - HR: 1.11, 95% CI: 1.05-1.16, per 10 mL/min/1.73 m2 decline in eGFRCys). This interaction effect was also demonstrated for eGFRCr-Cys, but not eGFRCr. eGFRCys and eGFRCr-Cys were more strongly associated with major bleeding and all-cause mortality than eGFRCr in both men and women. Event numbers were small for haemorrhagic stroke.

DISCUSSION

To a greater degree than is seen in men, eGFRCr underestimates risk of ischaemic stroke and major bleeding in women compared to eGFRCys. The difference between measures is likely explained by non-GFR biology of creatinine and cystatin C.

CONCLUSION

Enhanced measurement of cystatin C may improve risk stratification for ischaemic stroke and major bleeding and clinical treatment decisions in a general population setting, particularly for women.

Should Cystatin C eGFR Become Routine Clinical Practice?

Kidney function assessment is crucial for diagnosing and managing kidney diseases. Glomerular filtration rate (GFR) is widely used as an indicator of kidney function, but its direct measurement is challenging. Serum creatinine, a commonly used marker for estimating GFR (eGFR), has limitations in accuracy and sensitivity. Cystatin C, a protein freely filtered by the glomerulus, has emerged as a promising alternative marker for kidney function. It is unaffected by muscle mass and shows stronger associations with cardiovascular disease and mortality than creatinine. Various equations have been developed to estimate GFR using creatinine or cystatin C alone or in combination. The CKD-EPI_creat-cys equation combining both markers demonstrates improved accuracy in GFR estimation, especially for individuals with eGFR values of 45-59 mL/min/1.73 m². Cystatin C-based estimates of GFR outperform creatinine-based estimates in predicting clinical outcomes and identifying patients at higher risk, particularly in elderly and non-white ethnic groups. Cystatin C offers advantages over creatinine as a marker of kidney function. It is not influenced by non-kidney factors and provides more accurate estimation of GFR, aiding in the early detection of kidney disease and predicting adverse outcomes. Incorporating cystatin C into routine kidney function assessment may improve patient risk stratification and guide clinical decision-making. However, widespread adoption of cystatin C testing requires increased availability and accessibility in clinical laboratories. Further research and implementation efforts are needed to fully realize the potential of cystatin C in kidney function assessment and improving patient outcomes.

Estimation of glomerular filtration rate in cardiorenal patients: a step forward

The progressive reduction in estimated glomerular filtration rate (eGFR) resulting in chronic kidney disease (CKD) is associated with increased risk of cardiovascular disease (CVD) (i.e., cardiorenal disease). Cardiorenal disease is associated with poor outcomes, mainly due to increased cardiovascular (CV) complications and CV death. Data from general population-based studies and studies of cohorts with CKD and/or CVD show that compared with creatinine-based eGFR, cystatin C-based eGFR and creatinine plus cystatin C-based eGFR detect higher risks of adverse CV outcomes and add predictive discrimination to current CVD risk scores. On the other hand, growing clinical evidence supports kidney and CV protective effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors in cardiorenal patients. However, recent data suggest that some detrimental effects of SGLT2 inhibitors on skeletal muscle mass may lead to overestimation of creatinine-based eGFR and subsequent misinterpretation of associated CV risk in patients treated with these agents. Within this framework, we suggest the advisability of using cystatin C and/or creatinine plus cystatin C-based eGFR for routine clinical practice in cardiorenal patients to more accurately stratify CV risk and evaluate the kidney and CV protective effects of SGLT2 inhibitors. In this regard, we make a call to action to investigate the protective effects of these pharmacological agents using cystatin C-based eGFR.