Comparison of bias and accuracy using cystatin C and creatinine in CKD-EPI equations for GFR estimation

Nephrotoxicity Surveillance for Childhood and Young Adult Survivors of Cancer: Recommendations From the International Late Effects of Childhood Cancer Guideline Harmonization Group

PURPOSE

Childhood, adolescent, and young adult (CAYA) survivors of cancer are at risk of nephrotoxicity. Surveillance guidelines are important for timely diagnosis and treatment of these survivors, which could slow the progression to higher stages of kidney dysfunction.

METHODS

The International Late Effects of Childhood Cancer Guideline Harmonization Group established a multidisciplinary panel of 34 experts from 11 countries. The panel performed systematic literature reviews for articles published between 1990 and June 2023, graded the evidence using Grading of Recommendations Assessment, Development, and Evaluation methodology, and formulated recommendations based on evidence, clinical judgment, and consideration of benefits and harms of surveillance. Recommendations were critically appraised by two independent external experts and patient representatives.

RESULTS

Glomerular dysfunction surveillance is recommended every 2-5 years for survivors treated with ifosfamide, cisplatin, abdominal radiotherapy, total body irradiation, or nephrectomy and is reasonable after carboplatin treatment. We recommend screening for glomerular dysfunction using an estimated glomerular filtration rate (eGFR) equation that includes serum creatinine, preferably combined with serum cystatin C if available. Tubular dysfunction surveillance is recommended once at entry into long-term follow-up and with follow-up as clinically indicated for survivors treated with ifosfamide and is reasonable after cisplatin treatment.

CONCLUSION

These recommendations inform routine, uniform long-term follow-up care for CAYA survivors of cancer at risk of nephrotoxicity.

Better Prediction of Clinical Outcome with Estimated Glomerular Filtration Rate by CKD-EPI 2021

BACKGROUND

While the real-world impact of estimated glomerular filtration rate (eGFR) equation change on clinical outcome in a longitudinal cohort setting is limited, external valuation of equation performance should be performed in different population cohorts. This study aimed to compare differential impacts of eGFR values, calculated by 5 equations in a Korean patient population, on clinical outcomes.

METHODS

This retrospective longitudinal follow-up cohort study analyzed 23 246 participants with standardized creatinine/cystatin C assay-based laboratory results. The primary exposure was baseline eGFR calculated by 5 different equations including the recently developed 2021 race-free Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Clinical outcomes including all-cause mortality, renal replacement therapy, and albuminuria were analyzed to estimate the hazard ratio of the eGFR on clinical outcomes.

RESULTS

Among the 5 equations, CKD-EPI 2021 with creatinine and cystatin C (CKD-EPI 2021-CrCys) showed an earlier increase in hazard ratios for all clinical outcomes, while CKD-EPI 2012 with cystatin C showed a higher hazard ratio for all-cause mortality at low eGFR. Replacing CKD-EPI 2012 with CKD-EPI 2021-CrCys, 5.4% of patients with mortality and 3.3% of patients who received renal replacement therapy were reclassified to a lower risk stage.

CONCLUSIONS

The 2021 CKD-EPI equations were acceptable in a Korean population, with better predictive power for clinical outcomes when compared to previous equations. The updated race-free factors for eGFR calculation improved identification of patients at risk for clinical outcomes.

Long-Term Evolution of Renal Function Among People with HIV who Received Tenofovir Alafenamide-Containing Antiretroviral Therapy

INTRODUCTION

Among people with HIV (PWH), real-world data on the long-term renal function evolution while receiving tenofovir alafenamide (TAF)-containing antiretroviral therapy (ART) remain scarce.

METHODS

PWH who initiated or were switched to TAF-containing ART and controls who received non-tenofovir-containing ART were included for follow-up. We retrospectively collected demographic, clinical, and laboratory data, including estimated glomerular filtration rate (eGFR), urine β-2 microglobulin, and urine protein-to-creatinine ratio (UPCR). The association between the duration of ART exposure and change of eGFR was compared in locally estimated scatterplot smoothing (LOESS) regression. Factors associated with an excess decline of eGFR (defined as a decline > 2.5 ml/min/1.73 m2 per year; or > 25% throughout the observation) among TAF-receiving PWH were also evaluated.

RESULTS

Overall, 2422 PWH receiving TAF-containing regimens and 252 controls were included, with the median follow-up duration being 4.8 and 5.4 years, respectively. In the LOESS regression, the predicted change of eGFR at weeks 240 was - 8.0 (95% CI, - 9.1 to - 6.8) ml/min/1.73 m2 for TAF group, compared to - 11.1 ml/min/1.73 m2 (95% CI, - 15.4 to - 6.7) for non-TAF group. In the TAF group, 183 (7.6%) experienced an excessive renal function decline. Furthermore, the levels of urine β-2 microglobulin and UPCR remained stable throughout the observation. A higher plasma HIV RNA level, old age, presence of clinically significant proteinuria throughout observation, and having a higher eGFR at baseline were associated with an excessive decline of eGFR among TAF-receiving PWH.

CONCLUSIONS

Our study suggests that long-term exposure to TAF-containing ART was not associated with augmented eGFR declines among PWH.

A retrospective multi-site examination of chronic kidney disease using longitudinal laboratory results and metadata to identify clinical and financial risk

BACKGROUND

A retrospective observational study was conducted at 3 health care organizations to identify clinical gaps in care for patients with stage 3 or 4 chronic kidney disease (CKD), and financial opportunity from U.S. risk adjustment payment systems. Lack of evaluation for CKD in patients with diabetes was also assessed.

METHODS

Outpatient longitudinal laboratory results and patient metadata available in the electronic medical record, laboratory information system, and/or laboratory billing or facility claims data for the calendar year 2021 were evaluated. Laboratory results were compared to billing data (ICD-10 codes) and risk adjustment scores including Hierarchical Condition Categories (HCC) to determine if laboratory-identified CKD was coded as a disease condition in the electronic medical record. Adults 18 to 75 years of age were included; inpatient laboratory results and pregnant individuals were excluded.

RESULTS

At the 3 institutions, 12,478 of 16,063 (78%), 487 of 1511 (32%) and 19,433 of 29,277 (66%) of patients with laboratory evidence of stage 3 or 4 CKD did not have a corresponding ICD-10 or HCC code for CKD in the electronic medical record. For patients at the 3 institutions with diabetes on the basis of an HbA1c value of ≥ 6.5%, 34,384 of 58,278 (59%), 2274 of 2740 (83%) and 40,378 of 52,440 (77%) had not undergone guideline-recommended laboratory testing for CKD during the same 12 months. Using publicly available data for calendar year 2021, an estimated 3246 of 32,398 patients (9.9%) at the 3 institutions with undocumented CKD stages 3-4 would be enrolled in Medicare Advantage or Affordable Care Act Marketplace programs. The imputed lost reimbursement under risk-adjusted payment systems for under-documentation of CKD in this subset of patients was $2.85 M for the three institutions combined, representing lost opportunity for both identification and proactive clinical management of these patients, and financial recovery for the costs of providing that care.

CONCLUSIONS

Clinical laboratories can provide value beyond routine diagnostics, helping to close gaps in care for identification and management of CKD, stratifying subgroups of patients to identify risk, and capturing missed reimbursement through risk adjustment factors.

Predictive effect of estimated glomerular filtrate rate by creatinine or cystatin C on mortality in patients with coronary artery disease

BACKGROUND

Renal dysfunction leads to poor prognosis of patients with coronary artery disease (CAD). Current studies have reported the prognosis or mortality of various diseases using different estimated glomerular filtrate rate (eGFR) formulas, while the performance of these equations is unclear in CAD patients. We aim to evaluate the predict effect of creatinine-based eGFR (eGFRcr), cystatin C-based eGFR (eGFRcys), and both creatinine and cystatin C-based eGFR (eGFRcr-cys) in CAD patients.

METHODS

A total of 23,178 patients with CAD were included from CIN-II cohort study. The association of eGFRcr, eGFRcys and eGFRcr-cys with cardiovascular and all-cause mortality was detected by Cox regression analysis. The predictive effect of eGFRcr, eGFRcys and eGFRcr-cys on mortality was assessed.

RESULTS

During a median follow up of 4.3 years, totally 2051 patients (8.8%) experience all-cause mortality, of which 1427 patients (6.2%) died of cardiovascular disease. For the detection of cardiovascular mortality among CAD patients, eGFRcr-cys had high discriminatory capacity with area under the curve (AUC) in receiver operator characteristic analysis of 0.730, which was significantly better than eGFRcr (AUC = 0.707, p < 0.001) and eGFRcys (AUC = 0.719, p < 0.001). Similar results were observed in all-cause mortality. Restricted cubic spline showed a U-shaped association between eGFRcr and all outcomes in patients with both reduced and supranormal eGFR levels, while a L-shaped association in eGFRcys and eGFRcr-cys.

CONCLUSIONS

Estimated GFR based on both creatinine and cystatin C has highest predictive effect for cardiovascular and all-cause mortality among CAD patients. Meanwhile, supranormal eGFRcr may indicate a higher risk of mortality.

Evaluation of Race-Neutral Glomerular Filtration Rate Estimating Equations in an Indian Population

Introduction

Glomerular filtration rate (GFR) estimation equations have not been extensively validated in the Indian population. Preliminary data showed that the widely used creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPICr) 2009 significantly overestimated GFR in Indians. Newer estimated GFR (eGFR) equations based on creatinine and cystatin C, omitting the race, have been recently proposed. We investigated the performance of race-free eGFR equations in the Indian population.

Methods

Patients with chronic kidney disease (CKD) and potential kidney donors attending the outpatient clinic at the Postgraduate Institute of Medical Education and Research Chandigarh, India, were screened for enrolment. GFR was measured by urinary clearance of inulin and plasma clearance of iohexol. Performance of eGFR equations (CKD-EPICr(2021), CKD-EPICr-Cys(2021), CKD-EPICr(2009), CKD-EPICr-Cys(2012), CKD-EPICys, 2020Csy-B2M-BTP and 2020Cr-Csy-B2M-BTP, EKFCcr, EKFCcys, and EKFCcr-cys) were assessed against measured GFR (mGFR) using bias, precision, and accuracy (root mean square error [RMSE], mean absolute error [MAE] and P30 [% with eGFR within 30% of mGFR]).

Results

A total of 412 subjects (55% with CKD), average age 47 ± 11 years with an equal distribution of males and females were enrolled. The mean mGFR in the study population was 54.2 ± 30.2 ml/min per 1.73 m2. The average mGFR in the potential kidney donor's subgroup was 79.5 ± 23.2 ml/min per 1.73 m2. Bias was highest for creatinine-based eGFR equations (CKD-EPIcr(2021): -19.2 [-21.3 to -17.0] ml/min per 1.73 m2and CKD-EPIcr(2009): -17.0 [-19.1 to -15.0] ml/min per 1.73 m2). Cystatin C- (either alone or with other markers) based equations were slightly better but still did not reach P30 ≥ 80%.

Conclusions

Race-neutral CKD-EPICr(2021) equation did not significantly improve performance as compared to CKD-EPICr(2009) equation. These observations emphasize the need for developing new eGFR equations for Indians and to standardize the mGFR for easy access to care providers for individualized patient care.

Effect of Changing Estimated Glomerular Filtration Rate Formula on Sugammadex Use and Pulmonary Complications for African American and non-African American Patients

BACKGROUND

Sugammadex is associated with fewer postoperative pulmonary complications than is neostigmine reversal of neuromuscular blockade. However, the Food and Drug Administration-approved package insert states that its use is "not recommended" in severe renal impairment, separately defined as creatinine clearance <30 mL/min. Recently, the formula for estimating glomerular filtration rate (GFR) was updated to remove the race variable. Compared to the prior formula, the new consensus equation lowers the estimated GFR for African American patients and raises it for everyone else. We sought to determine how this change could differently impact the use of sugammadex, and thus the rate of pulmonary complications, for both African American and non-African American patients.

METHODS

We used Monte Carlo simulation models to estimate the difference in pulmonary complications that would be suffered by patients when the change in creatine clearance calculated from the estimated GFR (using the old race-based and new race-neutral Chronic Kidney Disease Epidemiology Collaboration formulas) crossed the 30 mL/min threshold, which would require a change in sugammadex or neostigmine use.

RESULTS

We found that 0.22% (95% confidence interval 0.14%-0.36%) of African American patients' creatinine clearance would drop from above to below 30 mL/min making sugammadex not recommended and 0.19% (0.16%-0.22%) of non-African American patients would have creatinine clearance increase to >30 mL/min making sugammadex now recommended. Based on our model, we estimate that African American patients would suffer (count [95% confidence interval]) 3 [0.4-6] more pulmonary complications per 100,000 African American patients who received rocuronium or vecuronium through the change from sugammadex to neostigmine reversal to comply with labeling recommendations. Conversely, the same change in formulas would reduce the number of non-African American patients suffering pulmonary complications by 3 [2-4] per 100,000.

CONCLUSIONS

The recent change in GFR formulas may potentially be associated with an increase in postoperative pulmonary complications in African American patients and a decrease in postoperative pulmonary complications in non-African American patients through GFR-driven changes in sugammadex use.

Obesity-related renal dysfunction: gender-specific influence of visceral adiposity and early impact of metabolic and bariatric surgery

Introduction

Renal dysfunction is a recognized complication of obesity with an incompletely characterized pathophysiology. Improvement of glomerular filtration rate (GFR) after metabolic and bariatric surgery (MBS) has been reported across all classes of renal function. Inter-gender differences with regard to correlates of renal function have been described, but the influence of body composition is an understudied area. We aimed to explore determinants of renal function in obesity and to assess its variations after MBS, with a focus on body composition parameters in males and females, respectively.

Materials methods

We conducted a retrospective study on 196 patients who underwent laparoscopic sleeve gastrectomy, evaluated preoperatively and 6 months after the intervention. Recorded data included clinical and biochemical assessment, as well as body composition estimation via dual-energy X-ray absorptiometry. Serum creatinine-based formulas were used for the estimation of GFR.

Results

We included a total of 196 patients (80 males and 116 females), with a mean age of 41.43 ± 10.79. Median baseline body mass index was 42.6 (6.61) kg/m2 and 6 months excess weight loss (EWL) reached 71.43 ± 17.18%, in females, estimated GFR correlated negatively with visceral adipose tissue (VAT) mass (rho=-.368) and this correlation was stronger in females with type 2 diabetes mellitus. Moreover, women in the third VAT mass tertile were 5 times more likely to have reduced GFR compared to the first tertile. Renal function improved after MBS across all classes of filtration. In males, this improvement correlated with EWL (rho=.358) and lean mass variation (rho=-.412), while in females it correlated with VAT mass variation (rho=-.266).

Conclusions

Our results are consistent with previous findings on the positive impact of MBS on renal function and suggest a more prominent impact of visceral adiposity on GFR in females.

Long-term association between water intake and kidney function in a population at high cardiovascular risk

OBJECTIVES

The evidence on water intake in the prevention of kidney function decline is scarce at population level in well-being individuals at high cardiovascular risk. Therefore, we aimed to longitudinally evaluate the associations between total water intake and subtypes and kidney function, through estimated-Glomerular Filtration Rate (eGFR).

METHODS

Three-year prospective analysis conducted in 1986 older adults (aged 55-75 year) with overweight/obesity and metabolic syndrome from the PREDIMED-Plus study. Water intake was assessed using validated beverage and food frequency questionnaires. Serum creatinine-based eGFR (SCr-based eGFR; ml/min/1.73 m2) was estimated using the CKD-EPI equation at baseline, one-year and 3-years of follow-up. Mixed-effects linear regression models were fitted to evaluate the associations between baseline total water intake and subtypes, and SCr-based eGFR over 3-years of follow-up.

RESULTS

Participants in the highest baseline tertile of total water intake, plain water and water from all fluids showed a lower decrease in SCr-based eGFR after 3-years of follow-up, compared to those in the lowest tertile. Participants with the highest tap water consumption showed a lower SCr-based eGFR decline after 1-year and 3-years of follow-up, in comparerd to participants in the lowest intake category (T3 vs. T1: β: 1.4 ml/min/1.73 m2; 95%CI: 0.5-2.3, β: 1.0; 95%CI: 0.1-2.0, respectively).

CONCLUSIONS

Plain water rather than other water sources, and especially tap water, was associated with lower kidney function decline assessed through eGFR over 3-years of follow-up, in older individuals at high cardiovascular risk.

TRIAL REGISTRATION

ISRCTN89898870. Retrospectively registered on 24 July 2014.

A Comparative Study on the Efficacy Between Cystatin C and Creatinine-Based Equations for Early Detection of Renal Damage in Patients of Eastern India

Chronic kidney disease (CKD) is one of the leading causes of mortality across the globe. Early diagnosis of the disease is important in order to prevent the adverse outcome related to CKD. Many laboratories adopt creatinine-based e-GFR equations which yields imprecise results leading to misdiagnosis of CKD. Emerging studies indicated cystatin C as a better renal marker than creatinine. The aim of the study is to compare the efficacy of CKD epidemiology collaboration (CKD-EPI) creatinine e-GFR equations with (CKD EPI) cystatin-based e-GFR equations alone and in combination with creatinine for early detection of CKD. A cross-sectional study employing 473 patients was conducted. Three estimating GFR equations were calculated based on creatinine and cystatin C. Pearson Correlation study was done to assess the correlation of creatinine and cystatin C with their respective GFRs. A predictive model was developed, and ROC curve was constructed to compare efficacy, sensitivity and specificity of the creatinine and cystatin C based equations. Cystatin C exhibited better negative correlation with GFR than creatinine in correlation study performed with three commonly employed eGFR equations including  CKD EPI Creatine cystatin C combined  equation (2021), cys C alone and CKD EPI  creatinine (2021)  equations respectively[r=(-) 0.801 vs. r=(-)0.786 vs. r=(-)0.773]. Predictive model demonstrated highest efficiency, sensitivity and specificity for creatinine-cystatin C combined equation (88%, 81% and 93%) followed by cystatin C alone equation (73%,63% and 82%) and creatinine-based equation  (61%, 56% and 66% respectively). The study showed better performance of cystatin C based equations for early detection of advance stages in chronic kidney disease as compared to creatinine-based e-GFR equation.

Comparison of plasma clearance of [51Cr]CrEDTA based on three, two and single samples to measure the glomerular filtration rate in patients with solid tumors: a prospective cross-sectional analysis

OBJECTIVES

[51Cr]CrEDTA is used to measure the Glomerular Filtration Rate (GFR) in different clinical conditions. However, there is no consensus on the ideal number of blood samples to be taken and at what time points to measure its clearance. This study aimed to compare Slope Intercept (SI) and Single-Sample (SS) methods for measuring GFR in patients with solid tumors, stratified by age, GFR, and Body Mass Index (BMI).

METHODS

1,174 patients with cancer were enrolled in this prospective study. GFR was calculated by the SI method using blood samples drawn 2-, 4-, and 6-hours after [51Cr]CrEDTA injection (246-GFR). GFR was also measured using the SI method with samples at 2 and 4 hours (24-GFR) and at 4 and 6 hours (46-GFR), and SS methods according to Groth (4Gr-GFR) and Fleming (4Fl-GFR). Statistical analysis was performed to assess the accuracy, precision, and bias of the methods.

RESULTS

Mean 246-GFR was 79.2 ± 21.9 mL/min/1.73 m2. ANOVA indicated a significant difference between 4Gr-GFR and the reference 246-GFR. Bias was lower than 5 mL/min/1.73 m2 for all methods, except for SS methods in subgroups BMI > 40 kg/m2; GFR > 105 or < 45. Precision was adequate and accuracy of 30 % was above 98% for all methods, except for SS methods in subgroup GFR < 45.

CONCLUSION

46-GFR and 246-GFR have high agreement and may be used to evaluate kidney function in patients with solid tumors. Single-sample methods can be adopted in specific situations, for non-obese patients with expected normal GFR.

Chronic kidney disease and its association with cerebral small vessel disease in the general older hypertensive population

BACKGROUND

Cerebral small vessel disease can be identified using magnetic resonance imaging, and includes white matter hyperintensities, lacunar infarcts, cerebral microbleeds, and brain atrophy. Cerebral small vessel disease and chronic kidney disease share many risk factors, including hypertension. This study aims to explore an association between chronic kidney disease and cerebral small vessel disease, and also to explore the role of hypertension in this relationship.

METHODS

With a cross sectional study design, data from 390 older adults was retrieved from the general population study Good Aging in Skåne. Chronic kidney disease was defined as glomerular filtration rate < 60 ml/min/1,73m2. Associations between chronic kidney disease and magnetic resonance imaging markers of cerebral small vessel disease were explored using logistic regression models adjusted for age and sex. In a secondary analysis, the same calculations were performed with the study sample stratified based on hypertension status.

RESULTS

In the whole group, adjusted for age and sex, chronic kidney disease was not associated with any markers of cerebral small vessel disease. After stratification by hypertension status and adjusted for age and sex, we observed that chronic kidney disease was associated with cerebral microbleeds (OR 1.93, CI 1.04-3.59, p-value 0.037), as well as with cortical atrophy (OR 2.45, CI 1.34-4.48, p-value 0.004) only in the hypertensive group. In the non-hypertensive group, no associations were observed.

CONCLUSIONS

In this exploratory cross-sectional study, we observed that chronic kidney disease was associated with markers of cerebral small vessel disease only in the hypertensive subgroup of a general population of older adults. This might indicate that hypertension is an important link between chronic kidney disease and cerebral small vessel disease. Further studies investigating the relationship between CKD, CSVD, and hypertension are warranted.

Associations between ultra-processed food consumption and kidney function in an older adult population with metabolic syndrome

BACKGROUND & AIMS

Ultra-processed food (UPF) consumption has increased dramatically over the last decades worldwide. Although it has been linked to some cardiometabolic comorbidities, there is limited evidence regarding kidney function. This study aimed to cross-sectionally and longitudinally assess the association between UPF consumption and estimated-glomerular filtration rate (eGFR) based on Cystatin C (CysC).

METHODS

Older adults (mean age 65 ± 5.0 years, 46% women) with overweight/obesity and metabolic syndrome (MetS) who had available data of CysC at baseline (n = 1909), at one-year and at 3-years of follow-up (n = 1700) were analyzed. Food consumption was assessed using a validated 143-item semi-quantitative food frequency questionnaire and UPF consumption (% of g/d) at baseline and changes after one-year of follow-up were estimated according to NOVA classification system. Multivariable-adjusted linear and logistic regression models were performed to evaluate the cross-sectional associations between UPF consumption with eGFR levels and decreased kidney function (eGFR <60 ml/min/1.73 m2) at baseline. Multivariable-adjusted mixed-effects linear regression models were fitted to investigate the associations between one-year changes in UPF and eGFR over 3-years of follow-up.

RESULTS

Individuals with the highest baseline UPF consumption showed lower eGFR (β: -3.39 ml/min/1.73 m2; 95% CI: -5.59 to -1.20) and higher odds of decreased kidney function (OR: 1.64; 95% CI: 1.21 to 2.22) at baseline, compared to individuals in the lowest tertile. Participants in the highest tertile of one-year changes in UPF consumption presented a significant decrease in eGFR after one-year of follow-up (β: -1.45 ml/min/1.73 m2; 95% CI: -2.90 to -0.01) as well as after 3-years of follow-up (β: -2.18 ml/min/1.73 m2; 95% CI: -3.71 to -0.65) compared to those in the reference category.

CONCLUSIONS

In a Mediterranean population of older adults with overweight/obesity and MetS, higher UPF consumption at baseline and one-year changes towards higher consumption of UPF were associated with worse kidney function at baseline and over 3-years of follow-up, respectively.

CLINICAL TRIAL REGISTRY NUMBER

ISRCTN89898870.

Comparison of glomerular filtration rate estimating equations in older adults: A systematic review and meta-analysis

BACKGROUND

Debates persist regarding the performance of existing glomerular filtration rate (GFR) estimating equations in older individuals. We performed this meta-analysis to assess the accuracy and bias of six commonly used equations, including the Chronic Kidney Disease Epidemiology Collaboration creatinine equation (CKD-EPICr) and its combination with cystatin C (CKD-EPICr-Cys), with the corresponding pair of the Berlin Initiative Study equations (BIS1 and BIS2) and the Full Age Spectrum equations (FASCr and FASCr-Cys).

METHODS

PubMed and the Cochrane Library were searched for studies comparing estimated GFR (eGFR) with measured GFR (mGFR). We analyzed the difference in P30 and bias among the six equations and investigated subgroups based on the area (Asian and non-Asian), mean age (60-74 years and ≥75 years), and levels of mean mGFR (<45 mL/min/1.73m2 and ≥45 mL/min/1.73m2).

RESULTS

27 studies with 18,112 participants were included, all reporting P30 and bias. BIS1 and FASCr exhibited significantly higher P30 than CKD-EPICr. While no significant differences were observed between FASCr and BIS1, or among the three combined equations in terms of either P30 or bias. Subgroup analyses revealed FASCr and FASCr-Cys achieved better results in most situations. However, in the subgroup of mGFR<45 mL/min/1.73m2, CKD-EPICr-Cys had relatively higher P30 and significantly smaller bias.

CONCLUSIONS

Overall, BIS and FAS provided relatively more accurate estimates of GFR than CKD-EPI in older adults. FASCr and FASCr-Cys may be better suited for various conditions, while CKD-EPICr-Cys would be a better option for older individuals with impaired renal function.

The potential of cystatin C as a predictive biomarker in pulmonary hypertension

BACKGROUND

Cystatin C is a novel biomarker to identify renal dysfunction and cardiovascular risk.

OBJECTIVE

The aim of this study was to investigate the role of cystatin C in non-invasive risk prediction in a large cohort of patients with pre-capillary pulmonary hypertension (PH).

METHOD

We retrospectively analyzed pre-capillary PH patients with available cystatin C and hemodynamic data derived from right heart catheterization.

RESULTS

A total of 398 consecutive patients with confirmed pre-capillary PH were recruited from Fuwai Hospital between November 2020 and November 2021. Over a median duration of 282 days, 72 (18.1%) of these patients experienced clinical worsening. Cystatin C levels significantly correlated with cardiac index (r = -0.286, P < 0.001), mixed venous oxygen saturation (r = -0.216, P < 0.001), and tricuspid annular plane systolic excursion (r = -0.236, P < 0.001), and high cystatin C levels independently predicted a poor prognosis after adjusting potential confounders in different models (all P < 0.05). A three-group non-invasive risk model was constructed based on the combined assessment of the cystatin C and WHO-FC using dichotomous cut-off value. Those patients with higher cystatin C (≥ 1.0 mg/L) and a worse WHO-FC experienced the highest risk of endpoint occurrence. The predictive capacity of this model was comparable to that of an existing invasive risk stratification model (area under curve: 0.657 vs 0.643, P = 0.619).

CONCLUSIONS

Cystatin C levels were associated with disease severity and prognosis in patients with pre-capillary PH. A combination of high cystatin C and advanced WHO-FC identifies patients at particularly high risk of clinical deterioration.

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.

Validation of the European Kidney Function Consortium Equation in Chinese Adult Population: An Equation Standing on the Shoulders of Predecessors

BACKGROUND

Equations based on serum creatinine (SCr) have been extensively applied to estimate glomerular filtration rate (GFR), but their performance is debatable. In 2021, the European Kidney Function Consortium (EKFC) published one novel SCr-based formula, which combined the feature of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and full age spectrum (FAS) equations, but its potential applications remain unknown. We seek to assess the appropriateness of the three equations in Chinese adults.

METHODS

A total of 3,692 participants (median age, 54 years) were included. Reference GFR (rGFR) was measured by the 99mTc-DTPA renal dynamic imaging method. Estimated GFR (eGFR) was calculated by the CKD-EPI, FAS, and EKFC equations. Correlation coefficients and Bland-Altman analysis were adopted to evaluate their validity. The performance was assessed in subgroups according to age, sex, rGFR, and SCr, considering the bias, accuracy, and precision.

RESULTS

The average rGFR was 74.2 mL/min/1.73 m2. eGFR by EKFC showed a relatively stronger correlation with rGFR (R = 0.749) and a larger area under the receiver operating characteristic curve (0.902). EKFC was significantly less biased and exhibited the highest P30 in the entire population (bias = 3.61, P30 = 73.3%). It also performed well in all analyzed subgroups, especially in participants with normal or slightly impaired renal function (rGFR≥60 mL/min/1.73 m2), and low SCr.

CONCLUSIONS

Compared to the other two SCr-based formulas, EKFC performed better in the Chinese. Thus, it might serve as a good alternative, until a more suitable formula is developed for the Chinese population.

Adipose tissue is associated with kidney function parameters

Obesity is characterized by the accumulation of adipose tissue in different body compartments. Whether adipose tissue directly affects kidney function is still unknown. We aimed to investigate the role of the adipose tissue and circulating creatinine, cystatin C and kidney function in subjects free of cardio-renal diseases. In the KORA-MRI population-based study, 377 subjects (mean age 56.2 ± 9.2 years; 41.6% female) underwent whole-body 3T-MRI examination. Adipose tissue defined as visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were quantified from T1-DIXON sequence using a semi-automatic algorithm. Serum creatinine and cystatin C were measured using standard laboratory and estimated glomerular filtration rate (e-GFR) was performed based on creatinine (e-GFR_crea), cystatin C (e-GFR_cys) and creatinine-cystatin C (e-GFR_cc). Linear regression analysis, adjusted for risk factors, was used to investigate the relationship between adipose tissue and circulating creatinine, cystatin C, and kidney function. In multivariate analyses VAT was inversely associated with eGFR_cys (ß = - 4.88, p =  < 0.001), and positively associated with serum cystatin C (ß = 0.05, p =  < 0.001), respectively. No association was found between other adipose parameters such as total adipose tissue (TAT) and subcutaneous adipose tissue (SAT) and serum creatinine, urine microalbumin and eGFR_crea. Stratified analyses according to BMI revealed confirmatory results for category of BMI > 30. VAT is positively associated with serum cystatin C and inversely with eGFR based on cystatin C, suggesting a direct involvement of visceral adipose tissue in increased metabolism of cystatin C and consequently decreased kidney function.

Osteopontin as a Biomarker in Chronic Kidney Disease

Osteopontin (OPN) is a ubiquitously expressed protein with a wide range of physiological functions, including roles in bone mineralization, immune regulation, and wound healing. OPN has been implicated in the pathogenesis of several forms of chronic kidney disease (CKD) where it promotes inflammation and fibrosis and regulates calcium and phosphate metabolism. OPN expression is increased in the kidneys, blood, and urine of patients with CKD, particularly in those with diabetic kidney disease and glomerulonephritis. The full-length OPN protein is cleaved by various proteases, including thrombin, matrix metalloproteinase (MMP)-3, MMP-7, cathepsin-D, and plasmin, producing N-terminal OPN (ntOPN), which may have more detrimental effects in CKD. Studies suggest that OPN may serve as a biomarker in CKD, and while more research is needed to fully evaluate and validate OPN and ntOPN as CKD biomarkers, the available evidence suggests that they are promising candidates for further investigation. Targeting OPN may be a potential treatment strategy. Several studies show that inhibition of OPN expression or activity can attenuate kidney injury and improve kidney function. In addition to its effects on kidney function, OPN has been linked to cardiovascular disease, which is a major cause of morbidity and mortality in patients with CKD.

Comparison of the association intensity of creatinine and cystatin C with hyperphosphatemia and hyperparathyroidism in patients with chronic kidney disease

Herein, we compared the association intensity of estimated glomerular filtration rate (eGFR) equations using creatinine (Cr) or cystatin C (CysC) with hyperphosphatemia and secondary hyperparathyroidism occurrence, which reflect the physiological changes occurring during chronic kidney disease (CKD) progression. This study included 639 patients treated between January 2019 and February 2022. The patients were divided into low- and high-difference groups based on the median value of the difference between the Cr-based eGFR (eGFRCr) and CysC-based eGFR (eGFRCysC). Sociodemographic and laboratory factors underlying a high difference between eGFRCr and eGFRCysC were analyzed. The association intensity of eGFRCr, eGFRCysC and both Cr- and CysC-based eGFR (eGFRCr-CysC) was compared using the area under the receiver operating characteristic curve (AuROC) values for hyperphosphatemia and hyperparathyroidism occurrence in the overall cohort and the low- and high-difference groups. Age > 70 years and CKD grade 3 based on eGFRCr were significant factors affecting the high differences. eGFRCysC and eGFRCr-CysC showed higher AuROC values than that of eGFRCr, especially in the high-difference group and in patients with CKD grade 3. Our results show that CysC should be evaluated in patients with significant factors, including age > 70 years and CKD grade 3, to accurately assess kidney function to better determine the physiological changes in CKD progression and predict prognosis accurately.

Kidney disease burden in an Asian Indian population: Effect of the new 2021 serum creatinine CKD-EPI equation

AIMS

CKD-EPI (chronic kidney disease-epidemiological) serum creatinine equation is widely accepted for calculating estimated glomerular filtration rate (eGFR). The effect of transitioning from the older 2009 to the newer race-independent 2021 CKD-EPI equation on the estimated kidney disease burden (eKDB) was studied in an Asian-Indian population.

METHODS

The study included 1156 adults, the two equations were compared for agreement (Bland-Altman and Cohen's kappa) and concordance (Lin's correlation and test for proportions).

RESULTS

The 2021 CKD-EPI increased the eGFR (positive-bias), independent of age-group, gender or presence of type 2 diabetes mellitus (T2DM) and hypertension (HTN). Thus, the eKDB was significantly decreased by 2021 CKD-EPI equation. The agreement was highest for the age-group 31-40 years (95.8 % versus 87.5 % for > 50 years). Besides, the eGFR category was shifted from G3 to G1 in 8.2 % (95 % CI: 6.8-9.9) individuals by 2021 CKD-EPI. The effect of transition on eKDB was greater in individuals > 50 years (7.4 %) or with HTN (6.3 %).

CONCLUSION

In comparison to the old equation, the 2021 CKD-EPI equation increased the eGFR, lowering the eKDB in this Asian-Indian cohort. The degree of lowering was affected by age-group, and presence of T2DM /HTN, but independent of gender.

Diagnostic biomolecules and combination therapy for pre-eclampsia

Pre-eclampsia (PE), associated with placental malperfusion, is the primary reason for maternal and perinatal mortality and morbidity that can cause vascular endothelial injury and multi-organ injury. Despite considerable research efforts, no pharmaceutical has been shown to stop disease progression. If women precisely diagnosed with PE can achieve treatment at early gestation, the maternal and fetal outcomes can be maximally optimized by expectant management. Current diagnostic approaches applying maternal characteristics or biophysical markers, including blood test, urine analysis and biophysical profile, possess limitations in the precise diagnosis of PE. Biochemical factor research associated with PE development has generated ambitious diagnostic targets based on PE pathogenesis and dissecting molecular phenotypes. This review focuses on current developments in biochemical prediction of PE and the corresponding interventions to ameliorate disease progression, aiming to provide references for clinical diagnoses and treatments.

Estimation of glomerular filtration rate for drug dosing in patients with very high or low body mass index

An accurate estimated glomerular filtration rate (eGFR) is essential in drug dosing. This study demonstrates the limitations of indexed (ml/min/1.73 m2 ) and de-indexed (ml/min) eGFR based drug dosing in patients with obesity or underweight. This systematic study aimed to determine the most appropriate approach to estimate the GFR for standardized eGFR based drug dosing in these patients. (Raw) data of 12 studies were selected to investigate the accuracy and bias of both the indexed and de-indexed estimations of the Modification of Diet in Renal Disease (MDRD) study equation and the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI), and of the Cockcroft-Gault (CG) in patients with obesity or underweight. Accuracy was calculated as the proportion of eGFR values within 30% of the measured GFR (P30) using an inert tracer (e.g., iohexol, inulin, 51 Cr-EDTA, or iothalamate clearance). An accuracy of at least 80% was considered acceptable. GFR values estimated with the CG, MDRD, and CKD-EPI differ significantly within a patient with obesity or underweight regardless of whether it is indexed or de-indexed. All studies, with two exceptions, show that all three equations are inaccurate for patients with underweight or class II obesity (P30: 55%-94%). De-indexing eGFR improves not or modestly the accuracy, and mostly remains below the 80% (P30: 62%-100%). CG was highly inaccurate in obese and underweight patients (P30: 7%-82%). Although these results show that CG is obsolete, the accuracy of MDRD and CKD-EPI is low in patients with obesity or underweight and de-indexing is not the solution. Better education and more accurate methods for appropriate drug dosing (e.g., measured GFR with inert tracer, therapeutic drug monitoring, or 24-h creatinine clearance) are recommended.

European Kidney Function Consortium Equation vs. Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Refit Equations for Estimating Glomerular Filtration Rate: Comparison with CKD-EPI Equations in the Korean Population

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most commonly used equation for estimated glomerular filtration rate (eGFR). Recently, the European Kidney Function Consortium (EKFC) announced a full-age spectrum equation, and the CKD-EPI announced the CKD-EPI refit equations (CKD-EPI-R). We compared CKD-EPI, EKFC, and CKD-EPI-R equations in a large-scale Korean population and investigated their potential implications for CKD prevalence. In a total of 106,021 individuals who received annual check-ups from 2018 to 2020, we compared the eGFR equations according to the Clinical and Laboratory Standards Institute guidelines. Weighted kappa (κ) agreement was used to compare the potential implications for CKD prevalence across the equations. The median value of eGFR tended to increase in the order of EKFC, CKD-EPI, and CKD-EPI-R equations (92.4 mL/min/1.73 m², 96.0 mL/min/1.73 m², and 100.0 mL/min/1.73 m², respectively). The EKFC and CKD-EPI-R equations showed a very high correlation of eGFR and good agreement for CKD prevalence with CKD-EPI equation (r = 0.98 and 1.00; κ = 0.80 and 0.82, respectively). Compared with the CKD-EPI equation, the EFKC equation overestimated CKD prevalence (3.5%), and the CKD-EPI-R equation underestimated it (1.5%). This is the first study comparing CKD-EPI, EKFC, and CKD-EPI-R equations simultaneously. The EKFC and CKD-EPI-R equations were statistically interchangeable with CKD-EPI equations in this large-scale Korean population. The transition of eGFR equations, however, would lead to sizable changes in the CKD prevalence. To improve kidney health, in-depth discussion considering various clinical aspects is imperative for the transition of eGFR equations.

Chronic Kidney Disease with Mild and Mild to Moderate Reduction in Renal Function and Long-Term Recurrences of Atrial Fibrillation after Pulmonary Vein Cryoballoon Ablation

The aim of this research was to evaluate if patients with chronic kidney disease (CKD) and mild or mild to moderate depression of renal function have an increased risk of atrial fibrillation (AF) recurrences after cryoballoon (CB) ablation. We performed a retrospective analysis of AF patients undergoing pulmonary vein isolation (PVI) by CB. The cohort was divided according to the KDIGO CKD-EPI classification into a (1) normal, (2) mildly decreased, or (3) mild to moderate reduction in estimated glomerular filtration rate (eGFR). Freedom from AF recurrences was the primary endpoint. A total of 1971 patients were included (60 ± 10 years, 29.0% females, 73.6% paroxysmal AF) in the study. Acute success and complication rates were 99.2% and 3.7%, respectively, with no significant differences among the three groups. After a follow-up of 24 months, AF recurrences were higher in the mildly and mild to moderate CKD groups compared to the normal kidney function group (23.4% vs. 28.3% vs. 33.5%, p < 0.05). Mild to moderate CKD was an independent predictor of AF recurrences after the blanking period (hazard ratio:1.38, 95% CI 1.02−1.86, p = 0.037). In conclusion, a multicenter analysis of AF patients treated with cryoablation revealed mild to moderate reductions in renal functions were associated with a higher risk of AF recurrences. Conversely, the procedural success and complication rates were similar in patients with normal, mildly reduced, or mild to moderate reduction in eGFR.

The Treatment of Heart Failure in Patients with Chronic Kidney Disease: Doubts and New Developments from the Last ESC Guidelines

Patients with heart failure (HF) and associated chronic kidney disease (CKD) are a population less represented in clinical trials; additionally, subjects with more severe estimated glomerular filtration rate reduction are often excluded from large studies. In this setting, most of the data come from post hoc analyses and retrospective studies. Accordingly, in patients with advanced CKD, there are no specific studies evaluating the long-term effects of the traditional drugs commonly administered in HF. Current concerns may affect the practical approach to the traditional treatment, and in this setting, physicians are often reluctant to administer and titrate some agents acting on the renin angiotensin aldosterone system and the sympathetic activity. Therefore, the extensive application in different HF subtypes with wide associated conditions and different renal dysfunction etiologies remains a subject of debate. The role of novel drugs, such as angiotensin receptor blocker neprilysin inhibitors and sodium glucose linked transporters 2 inhibitors seems to offer a new perspective in patients with CKD. Due to its protective vascular and hormonal actions, the use of these agents may be safely extended to patients with renal dysfunction in the long term. In this review, we discussed the largest trials reporting data on subjects with HF and associated CKD, while suggesting a practical stepwise algorithm to avoid renal and cardiac complications.

Treatment of Chronic Kidney Disease with Extracellular Vesicles from Mesenchymal Stem Cells and CD133+ Expanded Cells: A Comparative Preclinical Analysis

Chronic kidney disease (CKD) is characterized by structural abnormalities and the progressive loss of kidney function. Extracellular vesicles (EVs) from human umbilical cord tissue (hUCT)-derived mesenchymal stem cells (MSCs) and expanded human umbilical cord blood (hUCB)-derived CD133⁺ cells (eCD133⁺) maintain the characteristics of the parent cells, providing a new form of cell-free treatment. We evaluated the effects of EVs from hUCT-derived MSCs and hUCB-derived CD133⁺ cells on rats with CDK induced by an adenine-enriched diet. EVs were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis (NTA) and electron microscopy. The animals were randomized and divided into the MSC-EV group, eEPC-EV group and control group. Infusions occurred on the seventh and 14th days after CKD induction. Evaluations of kidney function were carried out by biochemical and histological analyses. Intense labeling of the α-SMA protein was observed when comparing the control with MSC-EVs. In both groups treated with EVs, a significant increase in serum albumin was observed, and the increase in cystatin C was inhibited. The results indicated improvements in renal function in CKD, demonstrating the therapeutic potential of EVs derived from MSCs and eCD133⁺ cells and suggesting the possibility that in the future, more than one type of EV will be used concurrently.

Neurofilament light chain concentration in an aging population

BACKGROUND

Neurofilament light chain (NF-L) concentration is recognized to be modified in neurological diseases and traumatic brain injuries, but studies in the normal aging population are lacking. It is, therefore, urgent to identify influencing factors of NF-L concentration in the aging population.

METHOD

We assessed NF-L concentration in sera of a large cohort of 409 community-dwelling adults aged over 65 years. We studied the association between NF-L and various physiological factors but also with self-reported comorbidities or life-style habits.

RESULTS

We showed that NF-L concentration in serum was tightly associated with cystatin C concentration (r = 0.501, p < 0.0001) and consequently, to the estimated glomerular filtration rate (eGFR) (r = - 0.492; p < 0.0001). Additionally, NF-L concentration was dependent on age and body mass index (BMI) but not sex. Among the self-reported comorbidities, subjects who reported neurological disorders, cardiovascular diseases or history of fracture had higher NF-L concentration in univariate analysis, whereas it was only the case for subjects who reported neurological disorders in the multivariate analysis. NF-L concentration was also increased when Mini-Mental State Examination (MMSE) was decreased (≤ 25 points) but not when geriatric depression score (GDS) was increased (> 5 points) in both univariate and multivariate analysis. Finally, we are providing reference ranges by age categories for subjects with or without altered renal function.

CONCLUSION

NF-L concentration in the aging population is not driven by the increasing number of comorbidities or depression. Yet, NF-L blood concentration is dependent on kidney function and NF-L interpretation in patients suffering from renal failure should be taken with caution.

High remnant cholesterol level is relevant to diabetic retinopathy in type 2 diabetes mellitus

Background

Diabetic retinopathy (DR) is the primary oculopathy causing blindness in diabetic patients. Currently, there is increasing interest in the role of lipids in the development of diabetic retinopathy, but it remains controversial. Remnant cholesterol (RC) is an inexpensive and easily measurable lipid parameter; however, the relationship between RC and DR in type 2 diabetes mellitus (T2DM) has not been elucidated. This research investigates the relevance between RC levels and DR severity while building a risk prediction model about DR.

Methods

In this single-centre retrospective cross-sectional study. Each hospitalised T2DM patient had no oral lipid-lowering drugs in the past three months, and coronary angiography showed epicardial coronary artery stenosis of less than 50% and completed seven-field stereo photographs, fluorescein fundus angiography, and optical coherence tomography detection. The RC value is calculated according to the internationally recognised formula. Binary logistic regression was used to correct confounding factors, and the receiver operating characteristic (ROC) analysis was used to identify risk factors and assess the nomogram’s diagnostic efficiency.

Results

A total of 456 T2DM patients were included in the study. The RC levels in the DR team was higher [0.74 (0.60–1.12) mmo/l vs 0.54 (0.31–0.83) mmol/l P < 0.001] in the non-DR team. After adjusting for confounding elements, RC levels are still associated with DR risk (OR = 5.623 95%CI: 2.996–10.556 P < 0.001). The ratio of DR in every stage (except mild non-proliferative diabetic retinopathy) and DME in the high RC level team were further increased compared to the low-level team (all P < 0.001). After ROC analysis, the overall risk of DR was predicted by a nomogram constructed for RC, diabetes duration, and the neutrophil-lymphocyte ratio as 0.758 (95%CI 0.714–0.802 P < 0.001).

Conclusions

High RC levels may be a potential risk factor for diabetic retinopathy, and the nomogram does better predict DR. Despite these essential findings, the limitation of this study is that it is single-centred and small sample size analysis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01621-7.

Prospective Comparison of 24-Hour Urine Creatinine Clearance with Estimated Glomerular Filtration Rates in Chronic Renal Disease Patients of African Descent

BACKGROUND

The 24-hour (24-h) creatinine clearance (CrCl) is the most common method for measuring GFR in clinical laboratories. However, the limitations of CrCl have resulted in the widespread acceptance of mathematically derived estimated glomerular filtration rate (eGFR) using Cockcroft-Gault (CG), Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in predicting eGFR. The aim of the study was to compare 24-h CrCl with eGFR derived from these formulae and to identify which could be the best alternative.

METHOD

A prospective study was conducted involving 140 CKD patients. Creatinine and cystatin C concentrations were determined using the cobas 6000 analyzer. The eGFR was calculated using the CG formula, 4-variable MDRD and CKD-EPI equations, and Bland-Alman plots bias was determined.

RESULTS

The CG and MDRD formulas had mean eGFR values similar to CrCl and correlation coefficients (r) were highest for CG (0.906) and lowest for MDRD (0.799). The CG equation was in agreement with 24-h CrCl in all but stage V CKD while the MDRD equation compared well in all except Stage IV CKD. The CG equation was positively biased (0.9857) while the MDRD had a negative bias (-0.05).

CONCLUSION

The Cockcroft-Gault formula provides a more accurate assessment of GFR than 24-h CrCl and would be recommended as a substitute to provide the best estimate of GFR in our population.

Performance and Determinants of Serum Creatinine and Cystatin C-Based GFR Estimating Equations in South Asians

INTRODUCTION

The creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimated glomerular filtration rate (eGFR) equation was calibrated for the general Pakistan population (eGFRcr-PK) to eliminate bias and improve accuracy. Cystatin C-based CKD-EPI equations (eGFRcys and eGFRcr-cys) have not been assessed in this population, and non-GFR determinants of cystatin C are unknown.

METHODS

We assessed eGFRcys, eGFRcr-cys, and non-GFR determinants of cystatin C in a cross-sectional study of 557 participants (≥40 years of age) from Pakistan. We compared bias (median difference in measured GFR [mGFR] and eGFR), precision (interquartile range [IQR] of differences), accuracy (percentage of eGFR within 30% of mGFR), root mean square error (RMSE), and classification of mGFR <60 ml/min/1.73 m2 (area under the receiver operating characteristic curve [AUC] and net reclassification index [NRI]) among eGFR equations.

RESULTS

We found that eGFRcys underestimated mGFR (bias, 12.7 ml/min/1.73 m2 [95% confidence interval {CI} 10.7-15.2]). eGFRcr-cys did not improve performance over eGFRcr-PK in precision (P = 0.52), accuracy (P = 0.58), or RMSE (P = 0.49). Results were consistent among subgroups by age, sex, smoking, body mass index (BMI), and eGFR. NRI was 7.31% (95% CI 1.52%-13.1%; P < 0.001) for eGFRcr-cys versus eGFRcr-PK, but AUC was not improved (0.92 [95% CI 0.87-0.96] vs. 0.90 [95% CI 0.86-0.95]; P = 0.056). Non-GFR determinants of higher cystatin C included male sex, smoking, higher BMI and total body fat, and lower lean body mass.

CONCLUSION

eGFRcys underestimated mGFR in South Asians and eGFRcr-cys did not offer substantial advantage compared with eGFRcr-PK. Future studies are warranted to better understand the large bias in eGFRcys and non-GFR determinants of cystatin C in South Asians.