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.

Sex and the Relationship Between Cardiometabolic Risk Factors and Estimated GFR Decline: A Population-Based Cohort Study.

RATIONALE & OBJECTIVE: Females have a higher prevalence of chronic kidney disease (CKD) than males, but are less likely to be treated with kidney replacement therapy (KRT). We studied the interaction between sex and the association of cardiometabolic risk factors for the decline in kidney function over time. STUDY DESIGN: A population-based cohort study. SETTING & PARTICIPANTS: 1,127,731 adults living in Wales, UK, within the Secure Anonymised Information Linkage Databank. EXPOSURES: Sex and risk factors including age, estimated glomerular filtration rate (eGFR), cardiometabolic conditions, smoking, and socioeconomic deprivation. These risk factors were defined using primary care records. OUTCOMES: The yearly declines in eGFR and the risk of incident kidney failure defined as long-term KRT and/or sustained eGFR<15mL/min/1.73m2. ANALYTICAL APPROACH: Linear mixed effects models and Cox proportional hazards analysis. RESULTS: The average decline in eGFR age ≤73 was equal in males and females. After age 73, eGFR decline was faster in males than females, particularly for males with heart failure (males -1.22 mL/min/1.73m2 per year: 95% confidence interval (CI) -1.25 to -1.20 versus females -0.87mL/min/1.73m2: CI -0.89 to -0.85) and current smokers (males -1.58 mL/min/1.73m2 per year: CI -1.60 to -1.55 versus females -1.27 mL/min/1.73m2: CI -1.29 to -1.25). Socioeconomic deprivation was one of the most impactful risk factors on eGFR decline among females age >73, whereas cardiometabolic risk factors were more important among males. Older females at baseline were less likely to develop incident kidney failure than older males (p-value for age<0.001). LIMITATIONS: Study of people who were almost exclusively White and who had blood laboratory test data. Reliance on creatinine-based eGFR. Albuminuria and body mass index data were incomplete. CONCLUSIONS: eGFR decline was faster in males than in females especially in the setting of heart failure and smoking. Socioeconomic deprivation was an important risk factor associated with eGFR decline, particularly for females. While further work is required to explore less well-recognised risk factors these findings may inform clinical management strategies of CKD overall and within sex-specific groups.

Sex differences in cancer outcomes across the range of eGFR.

BACKGROUND AND HYPOTHESIS: People with chronic kidney disease (CKD) have increased incidence and mortality from most cancer types. We hypothesised that odds of presenting with advanced cancer may vary according to differences in eGFR, that this could contribute to increased all-cause mortality and that sex differences may exist. METHODS: Data were from Secure Anonymised Information Linkage Databank, including people with de-novo cancer diagnosis (2011-2017) and two kidney function tests within two years prior to diagnosis to determine baseline eGFR (mL/min/1.73m2). Logistic regression models determined odds of presenting with advanced cancer by baseline eGFR. Cox proportional hazards models tested associations between baseline eGFRcr and all-cause mortality. RESULTS: eGFR < 30 was associated with higher odds of presenting with advanced cancer of prostate, breast and female genital organs, but not other cancer sites. Compared to eGFR > 75-90, eGFR < 30 was associated with greater hazards of all-cause mortality in both sexes, but the association was stronger in females (female: HR 1.71, 95%CI 1.56-1.88; male versus female comparison HR 0.88, 95%CI 0.78-0.90). CONCLUSIONS: Lower or higher eGFR was not associated with substantially higher odds of presenting with advanced cancer across most cancer sites, but was associated with reduced survival. A stronger assocation with all-cause mortality in females compared to males with eGFR < 30 is concerning and warrants further scrutiny.

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.

Cardiovascular Eligibility Criteria and Adverse Event Reporting in Combined Immune Checkpoint and VEGF Inhibitor Trials.

Background: Combination therapy with immune checkpoint inhibitors (ICIs) and vascular endothelial growth factor inhibitors (VEGFIs) has improved cancer outcomes and is increasingly used. These drug classes are associated with cardiovascular toxicities when used alone, but heterogeneity in trial design and reporting may limit knowledge of toxicities in patients receiving these in combination. Objectives: The aim of this study was to assess consistency and clarity in definitions and reporting of cardiovascular eligibility criteria, baseline characteristics, and cardiovascular adverse events in ICI and VEGFI combination trials. Methods: A scoping review was conducted of phase 2 to 4 randomized controlled trials of ICI and VEGFI combination therapy for solid tumors. Trial cardiovascular eligibility criteria and baseline cardiovascular characteristic reporting in trial publications was assessed, and cardiovascular adverse event definitions and reporting criteria were also examined. Results: Seventeen trials (N = 10,313; published 2018-2022) were included. There were multiple cardiovascular exclusion criteria in 15 trials. No primary trial publication reported baseline cardiovascular characteristics. Thirteen trials excluded patients with prior heart failure, myocardial infarction, hypertension, or stroke. There was heterogeneity in defining cardiovascular conditions. "Grade 1 to 4" cardiovascular adverse events were reported when incidence was ≥5% to 25% in 15 trials. Incident hypertension was recorded in all trials, but other cardiovascular events were not consistently reported. No trial specifically noted the absence of cardiovascular events. Conclusions: In ICI and VEGFI combination trials, there is heterogeneity in cardiovascular exclusion criteria, reporting of baseline characteristics, and reporting of cardiovascular adverse events. This limits an optimal understanding of the incidence and severity of events relating to these combinations. Better standardization of these elements should be pursued. (Exclusions and Representation of Patients With Kidney Disease and Cardiovascular Disease in Drug Trials of the Novel Systemic Anti-Cancer Therapies VEGF-Signalling Pathway Inhibitors Alone or in Combination With Immune Checkpoint Inhibitors; CRD42022337942).

Change in physical activity and its association with decline in kidney function: A UK Biobank-based cohort study.

BACKGROUND: Previous research on the association between physical activity (PA) and kidney function is inconsistent. The association between muscle mass and serum creatinine (SCr) may have implications for interpreting the effect of PA on estimated glomerular filtration rate (eGFR). Few studies have reported changes in physical activity and changes in kidney function. METHODS: A cohort study was constructed using the UK Biobank. Changes in physical activity were self-reported as metabolic equivalent task (MET) minutes/week. eGFR was calculated using SCr and cystatin C (CysC). Cox and nonlinear regressions with restricted cubic splines were applied to explore the association between changes in physical activity and rapid decline of kidney function (RDKF, eGFR annual decrease ≥3 mL/min/1.73 m2), and the annual change of eGFR. An exploratory analysis of cardiorespiratory fitness as the exposure was conducted. RESULTS: Among 11 757 participants, the median follow-up time was 4.4 years. Participants whose PA decreased by 1000 MET minutes/week at the follow-up assessment had a 2% reduction in risk of developing RDKFSCr (HR = 0.98, 95% CI: 0.96, 1.00). In contrast, a 1000 MET minutes/week increase in PA was associated with a 4% reduction in risk of developing RDKFCysC (HR = 0.96, 95% CI: 0.93, 0.99). A PA increase of 1000 MET minutes/week was associated with eGFRCysC annual increase of 0.04 mL/min/1.73 m2 (95% CI: 0.03, 0.06) but no significant changes in eGFRSCr. CONCLUSIONS: In this general population study, there are differing associations between changes in PA and changes in kidney function depending on the kidney biomarker used. Increasing PA is modestly associated with improving annual eGFRCysC and reduced risk of RDKF.

Cystatin C- and Creatinine-based Estimated GFR Differences: Prevalence and Predictors in the UK Biobank.

Rationale & Objective: Large differences between estimated glomerular filtration rate (eGFR) based on cystatin C (eGFRcys) and creatinine (eGFRcr) occur commonly. A comprehensive evaluation of factors that contribute to these differences is needed to guide the interpretation of discrepant eGFR values. Study Design: Cohort study. Setting & Participants: 468,969 participants in the UK Biobank. Exposures: Candidate sociodemographic, lifestyle factors, comorbidities, medication usage, and physical and laboratory predictors. Outcomes: eGFRdiff, defined as eGFRcys minus eGFRcr, categorized into 3 levels: lower eGFRcys (eGFRdiff, less than -15 mL/min/1.73 m2), concordant eGFRcys and eGFRcr (eGFRdiff, -15 to < 15 mL/min/1.73 m2), and lower eGFRcr (eGFRdiff, ≥15 mL/min/1.73 m2). Analytical Approach: Multinomial logistic regression models were constructed to identify predictors of lower eGFRcys or lower eGFRcr. We developed 2 prediction models comprising 375,175 participants: (1) a clinical model using clinically available variables and (2) an enriched model additionally including lifestyle variables. The models were internally validated in an additional 93,794 participants. Results: Mean ± standard deviation of eGFRcys was 88 ± 16 mL/min/1.73 m2, and eGFRcr was 95 ± 13 mL/min/1.73 m2; 25% and 5% of participants were in the lower eGFRcys and lower eGFRcr groups, respectively. In the multivariable enriched model, strong predictors of lower eGFRcys were older age, male sex, South Asian ethnicity, current smoker (vs never smoker), history of thyroid dysfunction, chronic inflammatory disease, steroid use, higher waist circumference and body fat, and urinary albumin-creatinine ratio >300 mg/g. Odds ratio estimates for these predictors were largely inverse of those in the lower eGFRcr group. The model's area under the curve was 0.75 in the validation set, with good calibration (1.00). Limitations: Limited generalizability. Conclusions: This study highlights the multitude of demographic, lifestyle, and health characteristics that are associated with large eGFRdiff. The clinical model may identify individuals who are likely to have discrepant eGFR values and thus should be prioritized for cystatin C testing.

Estimated glomerular filtration rate (eGFR) based on cystatin C and creatinine may differ substantially within an individual. Although most clinicians are aware that creatinine is influenced by muscle mass, there are additional numerous lifestyle and health characteristics that may affect serum concentrations of either biomarker. Our analyses of 468,969 individuals in the UK Biobank identified independent predictors of large differences between eGFR based on cystatin C and eGFR based on creatinine, which may inform the interpretation of discrepant eGFR values within an individual. We developed models that may be implemented at a population level to help health systems identify individuals who are likely to have large differences between eGFR based on cystatin C and eGFR based on creatinine and thus should be prioritized for cystatin C testing.