Biomarkers in native and transplant kidneys: opportunities to improve prediction of outcomes in chronic kidney disease

Predictive models in chronic kidney disease: essential tools in clinical practice

PURPOSE OF REVIEW

The integration of risk prediction in managing chronic kidney disease (CKD) is universally considered a key point of routine clinical practice to guide time-sensitive choices, such as dialysis access planning or counseling on kidney transplant options. Several prognostic models have been developed and validated to provide individualized evaluation of kidney failure risk in CKD patients. This review aims to analyze the current evidence on existing predictive models and evaluate the different advantages and disadvantages of these tools.

RECENT FINDINGS

Since Tangri et al. introduced the Kidney Failure Risk Equation in 2011, the nephrological scientific community focused its interest in enhancing available algorithms and finding new prognostic equations. Although current models can predict kidney failure with high discrimination, different questions remain unsolved. Thus, this field is open to new possibilities and discoveries.

SUMMARY

Accurately informing patients of their prognoses can result in tailored therapy with important clinical and psychological implications. Over the last 5 years, the number of disease-modifying therapeutic options has considerably increased, providing possibilities to not only prevent the kidney failure onset in patients with advanced CKD but also delay progression from early stages in at-risk individuals.

Association of soluble ST2 with all-cause and cardiovascular mortality in renal transplant recipients: a single-centre cohort study

BACKGROUND

Soluble ST2 is a novel biomarker of myocardial fibrosis with an established role in prognostication of patients with heart failure. Its role in cardiovascular risk prediction for renal transplant recipients has not been investigated despite promising results for ST2 in other populations with renal disease.

METHODS

In this prospective cohort study, 367 renal transplant recipients were followed up for a median of 16.2 years to investigate the association of soluble ST2 concentration with all-cause mortality. Cardiovascular mortality and major adverse cardiovascular events were secondary outcomes. Cox regression models were used to calculate hazard ratios and 95% confidence intervals for ST2 before and after adjustments. ST2 concentration was analysed both as a continuous variable and following categorisation according to the recommended cut-point of 35 ng/ml.

RESULTS

A twofold higher ST2 concentration was associated with a 36% increased risk of all-cause mortality after adjustment for conventional cardiovascular risk factors and high-sensitivity C-reactive protein (adjusted hazard ratio 1.36; 95% confidence interval 1.06-1.75; p = 0.016). Associations with ST2 concentration were similar for cardiovascular events (adjusted hazard ratio 1.31; 95% confidence interval 1.00-1.73; p = 0.054), but were stronger for cardiovascular mortality (adjusted hazard ratio 1.61; 95% confidence interval 1.07-2.41; p = 0.022). Addition of ST2 to risk prediction models for mortality and cardiovascular events failed to improve their predictive accuracy.

CONCLUSIONS

ST2 is associated with, but does not improve prediction of, adverse outcomes in renal transplant recipients.

Cardiovascular Autonomic Neuropathy and its Association with Cardiovascular and All-cause Mortality in Patients with End-stage Renal Disease

Background End-stage renal disease frequently leads to increased cardiovascular mortality. Cardiovascular autonomic neuropathy (CAN) may be predictive of cardiac arrhythmias and sudden cardiac death in patients with end-stage renal disease. Methods A total of 70 patients with end-stage renal disease were included in the study. The assessment of cardiac dysautonomia was based on the four standardized tests performed at the baseline and, again, at the end of the study. The criteria for CAN included at least two abnormal test results. Results Fifty of 70 patients completed the study and were followed-up after one year. Out of the 50 patients, 44 (88%) had CAN at baseline. Twelve (24%) patients died at the one-year follow-up. Sudden cardiac death was reported in seven out of 12 (58%) patients. All seven patients who died had high dysautonomia scores (three abnormal tests) at the baseline. There was a significantly higher percentage of patients with all four abnormal tests amongst patients who died of any cause (56% vs. 17%; RR 6.07, 95% CI 1.29-28.49; p-value 0.02) or due to sudden cardiac death (43% vs. 10.5%; RR 6.37, 95% CI 1.03-39.36; p-value 0.04). All five patients who did not have CAN at the baseline developed this abnormality on repeat testing after one year. Conclusion The prevalence of CAN in patients with end-stage renal disease on maintenance hemodialysis was significantly higher. CAN was an independent predictor of all-cause and cardiovascular mortality, which highlights it as a risk stratification tool in patients with end-stage renal disease.

Rapid and Low-Cost CRP Measurement by Integrating a Paper-Based Microfluidic Immunoassay with Smartphone (CRP-Chip)

Traditional diagnostic tests for chronic diseases are expensive and require a specialized laboratory, therefore limiting their use for point-of-care (PoC) testing. To address this gap, we developed a method for rapid and low-cost C-reactive protein (CRP) detection from blood by integrating a paper-based microfluidic immunoassay with a smartphone (CRP-Chip). We chose CRP for this initial development because it is a strong biomarker of prognosis in chronic heart and kidney disease. The microfluidic immunoassay is realized by lateral flow and gold nanoparticle-based colorimetric detection of the target protein. The test image signal is acquired and analyzed using a commercial smartphone with an attached microlens and a 3D-printed chip–phone interface. The CRP-Chip was validated for detecting CRP in blood samples from chronic kidney disease patients and healthy subjects. The linear detection range of the CRP-Chip is up to 2 μg/mL and the detection limit is 54 ng/mL. The CRP-Chip test result yields high reproducibility and is consistent with the standard ELISA kit. A single CRP-Chip can perform the test in triplicate on a single chip within 15 min for less than 50 US cents of material cost. This CRP-Chip with attractive features of low-cost, fast test speed, and integrated easy operation with smartphones has the potential to enable future clinical PoC chronic disease diagnosis and risk stratification by parallel measurements of a panel of protein biomarkers.

Cardiac Autonomic Neuropathy Predicts All-Cause and Cardiovascular Mortality in Patients With End-Stage Renal Failure: A 5-Year Prospective Study

Introduction

Chronic renal disease is associated with increased cardiovascular (CV) mortality. Cardiac autonomic neuropathy (CAN) is predictive of mortality for diseases that affect the autonomic nervous system. We prospectively evaluated the prognostic value of indexes of left ventricular (LV) function and CAN in all-cause and CV mortality of patients with end-stage renal failure (ESRF).

Methods

A total of 133 patients with ESRF were recruited. LV function was evaluated by echocardiography, whereas cardiac autonomic function was assessed using the battery of the 4 standardized tests proposed by Ewing.

Results

A total of 123 of 133 (92.5%) patients completed the study and were followed for a mean of 4.9 ± 2.6 years. Mean LV ejection fraction (LVEF) was 50.9 ± 6.9%, whereas 70 (57.9%) patients had CAN. Sixty-nine all-cause and 36 CV deaths were recorded. The survival rates at 3, 5, and 7 years were 77.2%, 57.4%, and 33.7%, respectively. Multivariate analysis after adjustment for waist circumference, current smoking, history of diabetes, and coronary artery disease demonstrated that the only independent predictors of all-cause mortality during follow-up were age, serum triglycerides, LVEF, and presence of CAN. Competing risk regression analysis, after adjusting for waist circumference, coronary heart disease, serum glucose, and triglycerides, indicated that age and presence of CAN were independent risk factors for CV mortality.

Discussion

Age and presence of CAN are independent predictors of all-cause and CV mortality in patients with ESRF. The functionality of the cardiac autonomic nervous system activity can be used for the risk stratification in patients with ESRF.

Bcıı--RFLP profiles for serum amiloid A1 and mutated MEFV gene prevalence in chronic renal failure patients requiring long-term hemodialysis

BACKGROUND AND AIM

There is an increased mortality risk in long-term hemodialysis patients of renal failure due to the chronic inflammation. The relationship between the chronic renal failure (CRF) and the role of familial genetic markers remains incompletely understood. In the current study, it was aimed to find out the prevalence of common MEFV gene mutations and BcII polymorphism in serum amyloid A1 (SAA1) gene in chronic renal patients (CRF) who require long-term hemodialysis.

METHOD

Current cohort includes 242 CRF patients and 245 healthy individuals from the same population. Total genomic DNA was isolated from peripheral blood-EDTA samples and genotyping of target MEFV gene was carried out by reverse hybridization Strip Assay and real-time techniques. The SAA1 gene was genotyped by the BclI-RFLP method.

RESULTS

Increased mutated MEFV genotypes were found in current CRF patients when compared with the control group from the same ethnicity and the difference was statistically significant (Table 2) (OR: 4.9401, 95% CI: 3.0694-7.9509), p<0.0001. The most frequent point mutations were M694V and E148Q. The mutated T allel frequency in the SAA1 gene was also different when compared with the healthy controls and the difference was found to be statistically significant (χ2: 13.18; p=0.000).

CONCLUSIONS

The current results indicate the germ-line mutations in both genetic biomarkers (MEFV and SAA1 genes) that are related to inflammation and amyloidosis processes may play a crucial role in CRF pathogenesis due to the long-term chronic inflammation.

Acute kidney injury in kidney transplantation

PURPOSE OF REVIEW

Acute kidney injury (AKI) in transplant recipients is a prevalent condition with a broad list of potential inciting causes. This review highlights recent data describing the epidemiology and long-term consequences of transplant AKI, novel interventions in the management of delayed graft function (DGF), and noninvasive diagnostic strategies.

RECENT FINDINGS

The incidence and outcomes of nontransplant AKI are well documented, and similar data are emerging in the transplant setting with recent reports suggesting a high incidence rate and significant impact on long-term graft outcomes. DGF represents a 'pure' form of transplant AKI, and many interventional trials aiming to limit ischemia-reperfusion-induced injury have recently been reported or are currently ongoing. The search for accurate noninvasive predictors of DGF and acute rejection is ongoing and recent literature describes novel plasma and urine-based biomarkers as well as transcriptional profiling methods with high potential for clinical applicability.

SUMMARY

AKI in transplant recipients is a frequent occurrence with significant potential for poor long-term graft outcomes. Recent efforts to limit ischemia-reperfusion injury and diagnose transplant AKI via noninvasive methods may help to minimize the impact of AKI on future graft function.

Cross-Sectional Evaluation of Kidney Function in Hospitalized Patients: Estimated GFR Versus Renal Scintigraphy

<b><i>Background/Aims: </i></b>Accurate staging of chronic kidney disease (CKD) is very important. We tried to identify difference in GFR evaluation between CKD-EPI and Gates method with renal scintigraphy and which variables are associated with these differences. <b><i>Methods: </i></b>We retrospectively reviewed the records of 341 patients who underwent dynamic renal scintigraphy in the last 5 years. Patients were categorized according to KDIGO staging I to V, using the eGFR calculated with the CKD-EPI equation. Secondarily, we stratified patients according to treatment with renin-angiotensin system (RAS) inhibitors. <b><i>Results: </i></b>Gates method tends to underestimate GFR especially in CKD stage I (mean -22.2 ml/min) and II (mean -12.5 ml/min). The division in quartiles of ages showed an underestimation of GFR only in the first quartile of age (< 50 years old). Gates method underestimation of GFR was more pronounced in stage I patients treated with RAS inhibitors (mean -34.6 ml/min). The same occurs in stage II, even though to a lesser extent. <b><i>Conclusion: </i></b>The assessment of GFR by the Gates method must be carefully considered in the early stages of CKD, especially in younger patients. Moreover, the difference is more pronounced in patients treated with RAS inhibitors. Longitudinal studies will prove which method better predicts cardiovascular or renal events.