Risk Factors for CKD Progression: Overview of Findings from the CRIC Study

Prediction of diabetic kidney disease with machine learning algorithms, upon the initial diagnosis of type 2 diabetes mellitus

INTRODUCTION

Diabetic kidney disease (DKD) accounts for the majority of increased risk of mortality for patients with diabetes, and eventually manifests in approximately half of those patients diagnosed with type 2 diabetes mellitus (T2DM). Although increased screening frequency can avoid delayed diagnoses, this is not uniformly implemented. The purpose of this study was to develop and retrospectively validate a machine learning algorithm (MLA) that predicts stages of DKD within 5 years upon diagnosis of T2DM.

RESEARCH DESIGN AND METHODS

Two MLAs were trained to predict stages of DKD severity, and compared with the Centers for Disease Control and Prevention (CDC) risk score to evaluate performance. The models were validated on a hold-out test set as well as an external dataset sourced from separate facilities.

RESULTS

The MLAs outperformed the CDC risk score in both the hold-out test and external datasets. Our algorithms achieved an area under the receiver operating characteristic curve (AUROC) of 0.75 on the hold-out set for prediction of any-stage DKD and an AUROC of over 0.82 for more severe endpoints, compared with the CDC risk score with an AUROC <0.70 on all test sets and endpoints.

CONCLUSION

This retrospective study shows that an MLA can provide timely predictions of DKD among patients with recently diagnosed T2DM.

Toll-like receptor 4 mutation protects the kidney from Ang-II-induced hypertensive injury

Cellular autophagy is a protective mechanism where cells degrade damaged organelles to maintain intracellular homeostasis. Apoptosis, on the other hand, is considered as programmed cell death. Interestingly, autophagy inhibits apoptosis by degrading apoptosis regulators. In hypertension, an imbalance of autophagy and apoptosis regulators can lead to renal injury and dysfunction. Previously, we have reported that toll-like receptor 4 (TLR4) mutant mice are protective against renal damage, in part, due to reduced oxidative stress and inflammation. However, the detailed mechanism remained elusive. In this study, we tested the hypothesis of whether TLR4 mutation reduces Ang-II-induced renal injury by inciting autophagy and suppressing apoptosis in the hypertensive kidney. Male mice with normal TLR4 expression (TLR4N, C3H/HeOuJ) and mutant TLR4 (TLR4M, C3H/HeJLps-d) aged 10-12 weeks were infused with Ang-II (1000 ng/kg/d) for 4 weeks to create hypertension. Saline infused appropriate control were used. Blood pressure was increased along with increased TLR4 expression in TLR4N mice receiving Ang-II compared to TLR4N control. Autophagy was downregulated, and apoptosis was upregulated in TLR4N mice treated with Ang-II. Also, kidney injury markers plasma lipocalin-2 (LCN2) and kidney injury molecule 1 (KIM-1) were upregulated in TLR4N mice treated with Ang-II. Besides, increased nuclear translocation and activity of NF-kB were measured in Ang-II-treated TLR4N mice. TLR4M mice remained protected against all these insults in hypertension. Together, these results suggest that Ang-II-induced TLR4 activation suppresses autophagy, induces apoptosis and kidney injury through in part by activating NF-kB signaling, and TLR4 mutation protects the kidney from Ang-II-induced hypertensive injury.

Renal Histologic Analysis Provides Complementary Information to Kidney Function Measurement for Patients with Early Diabetic or Hypertensive Disease

BACKGROUND

Patients with diabetic or hypertensive kidney disease rarely undergo kidney biopsy because nephrologists commonly believe that biopsy-related risk outweighs the potential benefits of obtaining histologic information to guide clinical decisions. Although kidney function is acutely regulated, histologic changes such as interstitial fibrosis, tubular atrophy, and glomerulosclerosis may represent chronic kidney damage, and thus might provide additional information about disease severity. However, whether histologic analysis provides information complementary to clinically used kidney function measurements, such as eGFR and proteinuria, is unclear.

METHODS

We performed a standardized semiquantitative histologic analysis of 859 nephrectomies obtained from individuals with or without diabetes mellitus or hypertension and varying degrees of kidney dysfunction. Changes in glomeruli, tubules, interstitium, and the vasculature were scored using 17 descriptive parameters in a standardized manner. We used multivariable linear and logistic regression analyses and unbiased, hierarchical clustering to assess associations between histologic alterations and clinical variables.

RESULTS

At CKD stages 3-5, eGFR correlates reasonably well with the degree of glomerulosclerosis and interstitial fibrosis and tubular atrophy (IFTA). In patients with CKD stages 1-2, the degree of histologic damage was highly variable and eGFR poorly estimated the degree of damage. Individuals with diabetes mellitus, hypertension, or Black race had significantly more glomerulosclerosis and IFTA, at the same eGFR level. Inclusion of glomerulosclerosis improved the kidney function decline estimation, even at early disease stages.

CONCLUSIONS

Histologic analysis is an important complementary method for kidney disease evaluation, especially at early disease stages. Some individuals present with relatively severe structural damage despite preserved eGFR.

Clinical epidemiological analysis of cohort studies investigating the pathogenesis of kidney disease

In recent years, large cohort studies of patients with chronic kidney disease (CKD) have been established all over the world. These studies have attempted to analyze the pathogenesis of CKD using a large body of published evidence. The design of cohort studies is characterized by the measurement of the exposure prior to the occurrence of the outcome, which has the advantage of clarifying the temporal relationship between predictors and outcomes and estimating the strength of the causal relationship between predictors and multiple outcomes. Recent advances in biostatistical analysis methods, such as propensity scores and risk prediction models, are facilitating causal inference using higher quality evidence with greater precision in observational studies. In this review, we will discuss clinical epidemiological research of kidney disease based on the analysis of observational cohort data sets, with a focus on our previous studies.

Association of kidney functions with a cascade of care for diabetes and hypertension in two geographically distinct Indian cohorts

AIM

Type 2 diabetes (T2DM) and hypertension (HTN) are the main modifiable risk factors of chronic kidney disease (CKD), among the known traditional and non-traditional risk factors.

METHODS

We determined the prevalence and care-cascade of these modifiable CKD-risk factors and their association with socioeconomic status in adjoining Lucknow and Puducherry cities of India.

RESULTS

439 participants reported no CKD were recruited. Serum analysis revealed an Estimated Glomerular Filtration Rate (eGFR) ≥ 90 ml/min/1.73 m² in 60.36% of the population. Of them, 55.85% had HTN and/or T2DM as CKD-risk factors; however, less than half of this population was unaware of their CKD-risk status. Awareness and treatment were significantly higher in Puducherry and were associated with literacy, occupation, and residence place. Although the CKD-risk population was about two times higher in Puducherry than Lucknow, the populations with mild-low eGFR were comparable in the two regions. Moreover, in Lucknow, mild-low eGFR and low awareness were more prevalent among the younger participants (<30 years), relative to Puducherry.

CONCLUSIONS

Despite a higher prevalence of CKD-risk factors in Puducherry, populations with mild-low eGFR were comparable to Lucknow. More heightened awareness and better care cascade for CKD-risk factors in Puducherry may prevent or delay eGFR reduction.

Multiplex Serum Biomarker Assays Improve Prediction of Renal and Mortality Outcomes in Chronic Kidney Disease

BACKGROUND

We investigated the predictive value of 11 serum biomarkers for renal and mortality end points in people with CKD.

METHODS

Adults with CKD (n=139) were enrolled from outpatient clinics between February 2014 and November 2016. Biomarker quantification was performed using two multiplex arrays on a clinical-grade analyzer. Relationships between biomarkers and renal and mortality end points were investigated by random forests and Cox proportional hazards regression.

RESULTS

The cohort was 56% male. The mean age was 63 years and median (IQR) CKD-EPI eGFR was 33 (24-51) ml/min per BSA. A total of 56 (40%) people developed a composite end point defined as ≥40% decline in eGFR, doubling of serum creatinine, RRT, or death over median (IQR) follow-up of 5.4 (4.7-5.7) years. Prediction of the composite end point was better with random forests trained on serum biomarkers compared with clinical variables (area under the curve of 0.81 versus 0.78). The predictive performance of biomarkers was further enhanced when considered alongside clinical variables (area under the curve of 0.83 versus 0.81 for biomarkers alone). Patients (n=27, 19%) with high soluble TNF receptor-1 (≥3 ng/ml) and neutrophil gelatinase-associated lipocalin (≥156 ng/ml), coupled with low complement 3a des-arginine (<2368 ng/ml), almost universally (96%) developed the composite renal and mortality end point. C-reactive protein (adjusted hazard ratio, 1.4; 95% CI, 1.1 to 1.8), neutrophil gelatinase-associated lipocalin (adjusted hazard ratio, 2.8; 95% CI, 1.3 to 6.1) and complement 3a desarginine (adjusted hazard ratio, 0.6; 95% CI, 0.4 to 0.96) independently predicted time to the composite end point.

CONCLUSIONS

Outpatients with the triad of high soluble TNF receptor-1 and neutrophil gelatinase-associated lipocalin coupled with low complement 3a des-arginine had high adverse event rates over 5-year follow-up. Incorporation of serum biomarkers alongside clinical variables improved prediction of CKD progression and mortality. Our findings require confirmation in larger, more diverse patient cohorts.

Chronic Kidney Disease Progression and Transition Probabilities in a Large Preventive Cohort in Colombia

BACKGROUND

Variability in chronic kidney disease (CKD) progression is a well-known phenomenon that underlines the importance of characterizing the said outcome in specific populations. Our objectives were to evaluate changes in the estimated glomerular filtration rate (eGFR) over time and determine the frequency of dialysis admission and factors associated with this outcome, to estimate the rate of program's loss-to-follow-up and the probability of transition between CKD stages over time.

METHODS

The study type was an observational analytic retrospective cohort in patients treated in a CKD prevention program in Bogota, Colombia, between January 1, 2009, and December 31, 2013, with follow-up until December 31, 2018. Adult participants of 18 years of age or older with diagnosed CKD stages G3 or G4 were enrolled into a prevention program. For each patient, the rate of progression of CKD in ml/min/1.73 m2/year was estimated using the ordinary least-squares method. Dialysis initiation and program's loss-to-follow-up rates were calculated. Heat maps were used to present probabilities of transitioning between various CKD stages over time. Survival model with competing risks was used to evaluate factors associated with dialysis initiation.

RESULTS

A total of 2752 patients met inclusion criteria and contributed with 14133 patient-years of follow-up and 200 dialysis initiation events, which represents a rate of 1.4 events per 100 patient-years (95% CI 1.2 to 1.6). The median change of the eGFR for the entire cohort was -0.47 ml/min/1.73 m2 per year, and in the diabetic population, it was -1.55 ml/min/1.73 m2 per year. The program's loss-to-follow-up rate was 2.6 events per 100 patient-years (95% CI 2.3 to 2.9). Probabilities of CKD stage transitions are presented in heat maps. Female sex, older age, baseline eGFR, and serum albumin were associated with lower risk of dialysis initiation while CKD etiology diabetes, cardiovascular disease history, systolic blood pressure, blood urea nitrogen, and LDL cholesterol were associated with a higher likelihood of dialysis initiation.

CONCLUSIONS

A CKD secondary prevention program's key indicator is reported here, such as dialysis initiation, progression rate, and program drop-out; CKD progression appears to be correlated with diabetic status and timing of referral into the preventive program.

Acute Kidney Injury and Progressive Diabetic Kidney Disease: An Epidemiological Perspective

PURPOSE

Diabetic kidney disease (DKD) represents a unique subset of patients with chronic kidney disease (CKD). Acute kidney injury (AKI) is implicated in DKD progression; however, their interplay is not studied well. We studied risk factors for AKI and the effect of AKI on disease progression in a homogeneous group of patients with DKD.

PATIENTS AND METHODS

We conducted a retrospective open cohort study of patients with DKD at a single tertiary care centre between August 2016 - August 2019. Patients with a minimum follow-up of 2 years were included in the study. The incidence, etiology and risk factors for AKI were studied. The primary outcome studied was the effect of AKI on reduction in estimated glomerular filtration rate (eGFR) in DKD. Loss in eGFR by 50% and need for renal replacement therapy or reaching CKD stage V were studied as secondary outcomes.

RESULTS

Two hundred and ninety-two DKD patients meeting the study criteria with a follow-up of 29.57 (±4.3) months were included. The incidence of AKI was 31.1%. Sepsis was the most common etiology (61%). Proteinuria was an independent risk factor for AKI after adjusting for covariates (adjusted OR - 1.158; 95% CI (1.018-1.316); p=0.025). In patients with AKI, median decline in eGFR was 10.29 mL/min/1.73m2/year (IQR-5.58-13.84) which was significantly higher compared to patients with no AKI [eGFR 7.25 (IQR 5.06-11.38); p-0.014]. On subgroup analysis, sepsis-induced AKI (versus non-sepsis AKI; p<0.001) and higher AKI stage (stage 2/3 versus stage 1; p=0.019) were associated with a faster decline in eGFR.

CONCLUSION

AKI is common in patients with DKD with sepsis being the most common etiology. AKI in diabetic kidney disease is associated with a faster decline in eGFR. Baseline proteinuria is an independent risk factor for AKI.

COVID-19 in Patients with CKD in New York City

BACKGROUND

COVID-19 has affected millions of people, and several chronic medical conditions appear to increase the risk of severe COVID-19. However, our understanding of COVID-19 outcomes in patients with CKD remains limited.

METHODS

This was a retrospective cohort study of patients with and without CKD consecutively admitted with COVID-19 to three affiliated hospitals in New York City. Pre-COVID-19 CKD diagnoses were identified by billing codes and verified by manual chart review. In-hospital mortality was compared between patients with and without underlying CKD. Logistic regression was used to adjust this analysis for confounders and to identify patient characteristics associated with mortality.

RESULTS

We identified 280 patients with CKD, and 4098 patients without CKD hospitalized with COVID-19. The median age of the CKD group was 75 (65-84) years, and age of the non-CKD group 62 (48-75) years. Baseline (pre-COVID-19) serum creatinine in patients with CKD was 1.5 (1.2-2.2) mg/dl. In-hospital mortality was 30% in patients with CKD versus 20% in patients without CKD (P<0.001). The risk of in-hospital death in patients with CKD remained higher than in patients without CKD after adjustment for comorbidities (hypertension, diabetes mellitus, asthma, and chronic obstructive pulmonary disease), adjusted OR 1.4 (95% CI,1.1 to 1.9), P=0.01. When stratified by age, elderly patients with CKD (age >70 years) had higher mortality than their age-matched control patients without CKD. In patients with CKD, factors associated with in-hospital mortality were age (adjusted OR, 1.09 [95% CI, 1.06 to 1.12]), P<0.001, baseline and admission serum phosphorus (adjusted OR, 1.5 [95% CI, 1.03 to 2.1], P=0.03 and 1.4 [95% CI, 1.1 to 1.7], P=0.001), serum creatinine on admission >0.3 mg/dl above the baseline (adjusted OR 2.6 [95% CI, 1.2 to 5.4]P=0.01), and diagnosis of acute on chronic kidney injury during hospitalization (adjusted OR 4.6 [95% CI, 2.3 to 8.9], P<0.001).

CONCLUSIONS

CKD is an independent risk factor for COVID-19-associated in-hospital mortality in elderly patients. Acute-on-chronic kidney injury increases the odds of in-hospital mortality in patients with CKD hospitalized with COVID-19.