How should proteinuria be detected and measured?

The association between monocyte to high-density lipoprotein cholesterol ratio and chronic kidney disease in a Chinese adult population: a cross-sectional study

BACKGROUND

Monocyte to high-density lipoprotein cholesterol ratio (MHR) was confirmed as a novel inflammatory marker and strongly associated with the risk of several diseases. This study aimed to investigate the relationship between MHR and chronic kidney disease (CKD) in a Chinese adult population.

METHODS

In this cross-sectional study, 232,775 community-dwelling adults in Binhai who completed health checkups in 2021 were enrolled. Participants were categorized based on the MHR quartiles. Clinical characteristics of participants across different groups were compared using one-way ANOVA, Kruskal-Wallis h-test, and Chi-squared test as appropriate. Univariate and multivariable logistic regression analyses were taken to assess the relationship between MHR and the presence of CKD, as well as its association with low estimated glomerular filtration rate (eGFR) and proteinuria. Subgroup analyses were further executed to confirm the reliability of this relationship.

RESULTS

A total of 21,014 (9.0%) individuals were diagnosed with CKD. Characteristic indicators including waist circumference, body mass index (BMI), blood pressure (BP), serum uric acid (SUA), triglyceride, and fasting blood glucose (FBG) showed a gradual increase with higher MHR quartiles, whereas parameters such as age, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and eGFR decreased (p < .001). In the multivariable logistic regression analysis, we observed independent associations between MHR (per 1 SD increase) and CKD, as well as low eGFR and proteinuria, with odds ratio (ORs) and 95% confidence intervals (95%CIs) of 1.206 (1.186-1.225), 1.289 (1.260-1.319), and 1.150 (1.129-1.171), respectively (p < .001). Similar conclusions were confirmed in subgroup analysis stratified by gender, age, BMI, central obesity, hypertension, and diabetes mellitus, after justification for confounding factors.

CONCLUSION

Elevated MHR level was independently associated with the presence of CKD, suggesting that it might serve as a useful clinical tool for risk stratification, offering valuable insights to inform preventive and therapeutic approaches for clinicians in their routine medical practice.

Podocyte number and glomerulosclerosis indices are associated with the response to therapy for primary focal segmental glomerulosclerosis

Corticosteroid therapy, often in combination with inhibition of the renin-angiotensin system, is first-line therapy for primary focal and segmental glomerulosclerosis (FSGS) with nephrotic-range proteinuria. However, the response to treatment is variable, and therefore new approaches to indicate the response to therapy are required. Podocyte depletion is a hallmark of early FSGS, and here we investigated whether podocyte number, density and/or size in diagnostic biopsies and/or the degree of glomerulosclerosis could indicate the clinical response to first-line therapy. In this retrospective single center cohort study, 19 participants (13 responders, 6 non-responders) were included. Biopsies obtained at diagnosis were prepared for analysis of podocyte number, density and size using design-based stereology. Renal function and proteinuria were assessed 6 months after therapy commenced. Responders and non-responders had similar levels of proteinuria at the time of biopsy and similar kidney function. Patients who did not respond to treatment at 6 months had a significantly higher percentage of glomeruli with global sclerosis than responders (p < 0.05) and glomerulosclerotic index (p < 0.05). Podocyte number per glomerulus in responders was 279 (203-507; median, IQR), 50% greater than that of non-responders (186, 118-310; p < 0.05). These findings suggest that primary FSGS patients with higher podocyte number per glomerulus and less advanced glomerulosclerosis are more likely to respond to first-line therapy at 6 months. A podocyte number less than approximately 216 per glomerulus, a GSI greater than 1 and percentage global sclerosis greater than approximately 20% are associated with a lack of response to therapy. Larger, prospective studies are warranted to confirm whether these parameters may help inform therapeutic decision making at the time of diagnosis of primary FSGS.

Laboratory Analysis of the Renal Function Changes Under Long-Term Exposure to Extremely Low Ambient Temperatures: Case Report

The study subject was a healthy, 47-year-old man, a low temperature Guinness World Record holder. He spent 50 days alone in Rovaniemi, Lapland, and functioned in the ambient temperature ranging from +2°C to -37°C. He did not use sources of heat, he did not eat warm meals or drink hot water, and did not dry his clothes. He slept in an igloo, on an ice cover of 20-30 cm. He spent 10 hours a day in a sleeping bag and for the remaining time he walked, skied, or rode a bicycle, and practiced swimming. The aim of the study was a laboratory assessment of renal capacity in a man exposed to long-term extremely low ambient temperatures. The study was approved by the Ethical Committee at the Regional Medical Chamber in Krakow, Poland (approval No.: 194/KBL/OIL/2019). Twice during the observation, urine and blood were collected and analyzed: before and after the prolonged exposure to extremely low ambient temperatures. Changes were seen in many blood and urine parameters, but in urine, they were more significant. In urine, decreased values of sodium (by 53.9%), potassium (by 22.6%), creatinine (by 65.5%), urea (by 61.3%), uric acid (by 58.4%), and protein (by 50%) were observed. Neutrophil gelatinase-associated lipocalin (NGAL) increased by 34%. Absence of calcium oxalate excretion was reported relative to the value before the exposure to cold. In blood, increased values of interleukin-6 (by 60%) and β-2-microglobulin (by 26.9%) were observed. Erythropoietin decreased by 22.4%. No changes were noted in estimated glomerular filtration rate. The study subject lost 10 kg in weight. On the basis of the results obtained during the observation, it can be determined that the probable cause of changes in the laboratory results of the subject was the diet used, and not a dysfunction of the excretory system. The body weight loss and activation of compensating mechanisms focused on saving vitally important diet components, caused by the insufficient diet, exclude the theory of a negative effect of exposure to extremely low temperatures on renal filtration function.

Kidney Function, Albuminuria, and Risk of Incident Atrial Fibrillation: A Systematic Review and Meta-Analysis

RATIONALE & OBJECTIVE

Atrial fibrillation (AF) and chronic kidney disease (CKD) often coexist. However, it is not known whether CKD is an independent risk factor for incident AF. Therefore, we evaluated the association between markers of CKD-estimated glomerular filtration rate (eGFR) and albuminuria-and incident AF.

STUDY DESIGN

Systematic review and meta-analysis of cohort studies and randomized controlled trials.

SETTING & STUDY POPULATIONS

Participants with measurement of eGFR and/or albuminuria who were not receiving dialysis.

SELECTION CRITERIA FOR STUDIES

Cohort studies and randomized controlled trials were included that reported incident AF risk in adults according to eGFR and/or albuminuria.

ANALYTICAL APPROACH

Age- or multivariate-adjusted risk ratios (RRs) for incident AF were extracted from cohort studies, and RRs for each trial were derived from event data. RRs for incident AF were pooled using random-effects models.

RESULTS

38 studies involving 28,470,249 participants with 530,041 incident AF cases were included. Adjusted risk of incident AF was greater among participants with lower eGFR than those with higher eGFR (eGFR<60 vs≥60mL/min/1.73m2: RR, 1.43; 95% CI, 1.30-1.57; and eGFR<90 vs≥90mL/min/1.73m2: RR, 1.42; 95% CI, 1.26-1.60). Adjusted incident AF risk was greater among participants with albuminuria (any albuminuria vs no albuminuria: RR, 1.43; 95% CI, 1.25-1.63; and moderately to severely increased albuminuria vs normal to mildly increased albuminuria: RR, 1.64; 95% CI, 1.31-2.06). Subgroup analyses showed an exposure-dependent association between CKD and incident AF, with the risk increasing progressively at lower eGFR and higher albuminuria categories.

LIMITATIONS

Lack of patient-level data, interaction between eGFR and albuminuria could not be evaluated, possible ascertainment bias due to variation in the methods of AF detection.

CONCLUSIONS

Lower eGFR and greater albuminuria were independently associated with increased risk of incident AF. CKD should be regarded as an independent risk factor for incident AF.

PLAIN-LANGUAGE SUMMARY

Irregular heartbeat, or atrial fibrillation (AF), is the commonest abnormal heart rhythm. AF occurs commonly in people with chronic kidney disease (CKD), and CKD is also common in people with AF. However, CKD in not widely recognized as a risk factor for new-onset or incident AF. In this research, we combined data on more than 28 million participants in 38 studies to determine whether CKD itself increases the chances of incident AF. We found that both commonly used markers of kidney disease (estimated glomerular filtration rate and albuminuria, ie, protein in the urine) were independently associated with a greater risk of incident AF. This finding suggests that CKD should be recognized as an independent risk factor for incident AF.

Proteinuria, measured or estimated albuminuria for risk prediction in patients with chronic kidney disease?

BACKGROUND

Although albuminuria is the gold standard for defining chronic kidney disease (CKD), total proteinuria has also been widely used in real-world clinical practice. Moreover, the superiority of the prognostic performance of albuminuria over proteinuria in patients with CKD remains inconclusive. Therefore, we aimed to compare the predictive performances of albuminuria and proteinuria in these patients.

METHODS

From the Korean Cohort Study for Outcome in Patients with CKD we included 2099 patients diagnosed with CKD grades 1-5 who did not require kidney replacement therapy. We measured the spot urine albumin:creatinine ratio (mACR) and protein:creatinine ratio (PCR) and estimated the ACR (eACR) using the PCR. Kidney failure risk equation (KFRE) scores were calculated using the mACR, PCR and eACR. The primary outcome was the 5-year risk of kidney failure with replacement therapy (KFRT).

RESULTS

The eACR significantly underestimated mACR in patients with low albuminuria levels. The time-dependent area under the receiver operating characteristics curve showed excellent predictive performance for all KFRE scores from the mACR, PCR and eACR. However, eACR was inferior to mACR based on the continuous net reclassification index (cNRI) and integrated discrimination improvement index (IDI) in all CKD cause groups, except for the group with an unclassified aetiology. Moreover, the cNRI and IDI statistics indicated that both eACR and PCR were inferior to mACR in patients with low albuminuria (<30 mg/g). Conversely, the predictive performance of PCR was superior in severe albuminuria and nephrotic-range proteinuria, in which the IDI and cNRI of the PCR were greater than those of the mACR.

CONCLUSIONS

The mACR, eACR and PCR showed excellent performance in predicting KFRT in patients with CKD. However, eACR was inferior to mACR in patients with low albuminuria, indicating that measuring rather than estimating albuminuria is preferred for these patients.

Proteinuria selectivity index in renal disease

One of the main barriers to early detection and subsequent prevention of kidney diseases is the accessibility and feasibility of testing, especially in urine research. The proteinuria selectivity index (PSI or SI) is a method used to assess changes in glomerular permeability in glomerular diseases. It describes the pattern of proteinuria by comparing the clearance rates of large molecular proteins and transferrin, categorizing it as selective or non-selective. PSI is widely applied for kidney disease classification, prediction of corticosteroid efficacy, and prognosis. Herein, we reviewed the clinical applications and recent advancements of PSI in glomerular diseases, compared it with commonly used renal function biomarkers, and discussed the future research directions for PSI as a potential predictive marker for response to specific biologics.

Donor Proteinuria and Allograft Function in Kidney Transplantation: Short- and Long-Term Results From a Retrospective Cohort Study

Donor proteinuria (DP) is a common but rarely evaluated aspect of today's kidney transplant allocation process. While proteinuria after kidney transplantation is a risk factor for impaired graft function and survival, the long-term effects of DP in kidney transplantation have not yet been evaluated. Therefore, this study aims to investigate the impact of DP on the long-term outcome after kidney transplantation. A total of 587 patients were found to be eligible and were stratified into two groups: (1) those receiving a graft from a donor without proteinuria (DP-) and (2) those receiving a graft from a donor with proteinuria (DP+). At 36 months, there was no difference in the primary composite endpoint including graft loss and patient survival (log-rank test, p = 0.377). However, the analysis of DP+ subgroups showed a significant decrease in overall patient survival in the group with high DP (p = 0.017). DP did not adversely affect patient or graft survival over 36 months. Nevertheless, this work revealed a trend towards decreased overall survival of patients with severe proteinuria in the subgroup analysis. Therefore, the underlying results suggest caution in allocating kidneys from donors with high levels of proteinuria.

Stimulator of interferon genes/Interferon regulatory factor 3 (STING-IRF3) and inflammasome-activation mediated pyroptosis biomarkers: a network of integrated pathways in diabetic nephropathy

Background

Diabetic Nephropathy (DN) is serious diabetic complication affecting the structure and function of the kidney. This study assessed the stimulator of interferon genes/ Interferon regulatory factor 3 (STING/IRF3) signaling pathway roles and inflammasome-activation mediated pyroptosis, being imperative pathways of inordinate importance in disease progression, in DN throughout its different stages.

Methods

45 Diabetic cases were categorized into three groups based on their albuminuric status as follow: Normoalbuminuric, Microalbuminuric and Macroalbuminuric diabetic groups and 15 healthy subjects as controls were included. We evaluated STING and absent in melanoma 2 (AIM2) messenger RNA (mRNA) expressions from whole blood using quantitative RT-PCR. Additionally, Serum levels of STING, AIM2, IRF3, Nod like receptor pyrins-3 (NLRP3), interleukin-1β (IL-1β) and caspase-1 were assessed by ELISA technique.

Results

The study documented that STING and AIM2 mRNA expressions had significantly increased in DN cases with highest value in macroalbuminuric diabetic groups (p < 0.001*). Parallel results were observed concerning serum STING, AIM2, IRF3, NLRP3, Caspase-1 in addition to IL-1β levels (p < 0.001*).

Conclusion

The study documented the forthcoming role of STING in DN progression and its positive correlation with inflammasome-activation mediated pyroptosis biomarkers throughout its three different stages; launching new horizons in DN pathogenesis by highlighting its role as a reliable prognostic biomarker.

Navigating the Crossroads: Understanding the Link Between Chronic Kidney Disease and Cardiovascular Health

Chronic Kidney Disease (CKD) has emerged as a global healthcare challenge affecting a significant portion of the world's population. This comprehensive narrative review delves into the intricate relationship between CKD and cardiovascular disease (CVD). CKD is characterized by kidney damage persisting for at least three months, often with or without a decline in glomerular filtration rate (GFR). It is closely linked with CVD, as individuals with CKD face a high risk of cardiovascular events, making cardiovascular-associated mortality a significant concern in advanced CKD stages. The review emphasizes the importance of precise risk assessment using biomarkers, advanced imaging, and tailored medication strategies to mitigate cardiovascular risks in CKD patients. Lifestyle modifications, early intervention, and patient-centered care are crucial in managing both conditions. Challenges in awareness and recognition of CKD and the need for comprehensive interdisciplinary care are highlighted. Recent advances in research offer promising therapies, such as SGLT2 inhibitors, MRAs, GLP-1R agonists, and selective endothelin receptor antagonists. Stem cell-based therapies, gene editing, and regenerative approaches are under investigation. Patient-physician "risk discussions" and tailored risk assessments are essential for improving patient outcomes. In conclusion, the review underscores the complexity of the interconnected CKD and cardiovascular health domains. Ongoing research, innovative therapies, and personalized healthcare will be instrumental in addressing the challenges, reducing the disease burden, and enhancing well-being for individuals facing CKD and cardiovascular issues. Recognizing the intricate connections between these conditions is imperative for healthcare providers, policymakers, and researchers as they seek to improve the quality of care and outcomes for affected individuals.

Measuring albuminuria or proteinuria: does one answer fit all?

Measurement of proteinuria is critical for diagnosing and monitoring kidney disease. A variety of measures are available to clinicians and can identify all urinary proteins (proteinuria) or urine albumin alone (albuminuria). Proteinuria and albuminuria can be measured in either a random urine sample or a timed urine collection (often over 24 hours). Although an international guideline advocates the use of the urinary albumin-to-creatinine ratio for most purposes, this measure is not universally available worldwide and historically has been more costly than alternatives. In addition, there may be important differences in accuracy between the albumin-to-creatinine ratio and others based on magnitude of albuminuria, sex, and certain clinical contexts. In this mini review, we review recommendations from international guidelines and discuss specific contexts where the optimal measure of proteinuria is unclear and, in some situations, controversial. We discuss the evidence supporting current recommendations for choice of measure, including the clinical settings of glomerulonephritis, transplantation, and pregnancy. We also discuss how patient sex and cost may impact this decision.

Degree of Albuminuria is Associated With Increased Risk of Fragility Fractures Independent of Estimated GFR

Introduction

Fragility fractures are common in persons with chronic kidney disease (CKD); however, the association between fragility fractures and albuminuria is not well-studied. The primary objective of this study is to determine the association of albuminuria with incident risk of fragility fractures. The secondary objective is to examine the risk of fragility fracture by estimated glomerular filtration rate (eGFR) and Kidney Disease Improving Global Outcomes (KDIGO) risk categories.

Methods

Community dwelling adults residing in Alberta, Canada who had at least 1 creatinine and albuminuria measurement between April 1, 2008 and March 31, 2019 participated in the study (N = 2.72 million). Incident fragility fractures were identified using Canadian Chronic Disease Surveillance Systems Osteoporosis Working Group algorithms. Albuminuria was categorized as none/mild (albumin-to-creatinine ratio [ACR] <30 mg/g, protein-to-creatinine ratio [PCR] <150 mg/g, trace/negative dipstick); moderate (ACR 30-300 mg/g, PCR 150-500 mg/g, 1+ dipstick) or severe (ACR >300 mg/g, PCR >500 mg/g, ≥2+ dipstick). Multivariable analysis controlled for 42 variables.

Results

Patients with severe albuminuria had an increased risk of hip fracture (odds ratio [OR] = 1.37; 95% confidence interval [CI] 1.28, 1.47]), vertebral fracture (OR = 1.31; 95% CI 1.21, 1.41) and any-type fracture (OR = 1.22; 95% CI 1.17, 1.28) compared with patients with none/mild albuminuria. Patients in the most severe KDIGO risk category had an increased risk of hip fracture (OR = 1.22; 95% CI 1.16, 1.29), vertebral fracture (OR = 1.18; 95% CI 1.09, 1.26) and any type of fracture (OR = 1.25; 95% CI 1.21, 1.30).

Conclusion

This study demonstrates the important role of albuminuria as a risk factor for fragility fractures in CKD and may help inform risk stratification and prevention strategies in this high-risk population category.

Urinary aberrations in systemic lupus erythematosus not always indicative of lupus nephritis: a cross-sectional cohort study

INTRODUCTION

Kidney biopsy is the reference tool for diagnosing and guiding treatment strategies in inflammatory renal diseases, such as lupus nephritis (LN). We investigated the histopathological findings in first-time kidney biopsies from a large cohort of SLE patients. We focused on the occurrence and type of histopathological findings other than LN, and fulfillment of renal criteria in established SLE classification systems were analyzed.

METHODS

We retrospectively included SLE patients (n = 139) who underwent a first kidney biopsy between 1995 and 2021, upon clinical suspicion of renal involvement. Based on histology, two groups were defined, LN and non-LN, for which clinical and laboratory features were compared.

RESULTS

Findings consistent with LN according to ISN/RPS classification system were present in 123/139 patients (88.5%) and findings not consistent with LN were present in 16 /139 (11.5%). Non-LN patients were older at SLE diagnosis compared to LN patients (M, years 38.0 vs. 30.1, p=0.013) and had longer disease duration (M, years 11.9 vs 0.5) (p=0.027). Among non-LN patients 85.7% met the SLICC criteria item for renal SLE, seen in 94.7% in the LN group (ns). For the ACR/EULAR criteria, 66.7% of the non-LN group fulfilled the criteria compared to 74.8% in LN patients (ns). Proteinuria below the criteria cut-off level (< 0.5 g/24 h) was seen in 20% of patients with class III/IV LN.

CONCLUSION

Our data confirm the importance of kidney biopsy for ruling out the presence of renal pathology other than LN. Patients with low-grade proteinuria may exhibit severe types of LN, which reinforces the need for early biopsies to detect LN. Key Points • Our findings show that histopathology changes other than lupus nephritis may occur in a significant number of patients with clinical and laboratory signs of novel kidney involvement. • Low-grade proteinuria does not exclude findings of active lupus nephritis that require the start of immunosuppressive therapy. • The study stresses the importance of performing kidney biopsies also in the presence of low-grade proteinuria or when signs of kidney function abnormalities occur. • This is crucial as early detection and prompt initiation of therapy may improve outcomes in lupus nephritis.

SERS for Detection of Proteinuria: A Comparison of Gold, Silver, Al Tape, and Silicon Substrates for Identification of Elevated Protein Concentration in Urine

Excessive protein excretion in human urine is an early and sensitive marker of diabetic nephropathy and primary and secondary renal disease. Kidney problems, particularly chronic kidney disease, remain among the few growing causes of mortality in the world. Therefore, it is important to develop an efficient, expressive, and low-cost method for protein determination. Surface enhanced Raman spectroscopy (SERS) methods are potential candidates to achieve these criteria. In this paper, a SERS method was developed to distinguish patients with proteinuria from the healthy group. Commercial gold nanoparticles (AuNPs) with diameters of 60 nm and 100 nm, and silver nanoparticles (AgNPs) with a diameter of 100 nm were tested on the surface of four different substrates including silver and gold films, silicon, and aluminum tape. SERS spectra were acquired from 111 unique human urine samples prepared and measured for each of the seven different nanoparticle plus substrate combinations. Data analysis by the PCA-LDA algorithm and the ROC curves gave results for the diagnostic figures of merits. The best sensitivity, specificity, accuracy, and AUC were 0.91, 0.84, 0.88, and 0.94 for the set with 100 nm Au NPs on the silver substrate, respectively. Among the three metal substrates, the substrate with AuNPs and Al tape performed slightly worse than the other three substrates, and 100 nm gold nanoparticles on average produced better results than 60 nm gold nanoparticles. The 60 nm diameter AuNPs and silicon, which is about one order of magnitude more cost-effective than AuNPs and gold film, showed a relative performance close to the performance of 60 nm AuNPs and Au film (average AUC 0.88 (Si) vs. 0.89 (Au)). This is likely the first reported application of unmodified silicon in SERS substrates applied for direct detection of proteins in any biofluid, particularly in urine. These results position silicon and AuNPs@Si in particular as a perspective SERS substrate for direct urine analysis, including clinical diagnostics of proteinuria.

Terahertz spectra of proteinuria and non-proteinuria

In clinical practice, proteinuria detection is of great significance in the diagnosis of kidney diseases. Dipstick analysis is used in most outpatient settings to semi-quantitatively measure the urine protein concentration. However, this method has limitations for protein detection, and alkaline urine or hematuria will cause false positive results. Recently, terahertz time-domain spectroscopy (THz-TDS) with strong hydrogen bonding sensitivity has been proven to be able to distinguish different types of biological solutions, which means that protein molecules in urine may have different THz spectral characteristics. In this study, we performed a preliminary clinical study investigating the terahertz spectra of 20 fresh urine samples (non-proteinuria and proteinuria). The results showed that the concentration of urine protein was positively correlated with the absorption of THz spectra at 0.5-1.2 THz. At 1.0 THz, the pH values (6, 7, 8, and 9) had no significant effect on the THz absorption spectra of urine proteins. The terahertz absorption of proteins with a high molecular weight (albumin) was greater than that of proteins with a low molecular weight (β2-microglobulin) at the same concentration. Overall, THz-TDS spectroscopy for the qualitative detection of proteinuria is not affected by pH and has the potential to discriminate between albumin and β2-microglobulin in urine.

A comparison of the utility of the urine dipstick and urine protein-to-creatinine ratio for predicting microalbuminuria in patients with non-diabetic lifestyle-related diseases -a comparison with diabetes

BACKGROUND

The utility of dipstick proteinuria for predicting microalbuminuria in non-diabetic lifestyle-related diseases compared with the urine protein-to-creatinine ratio (uPCR) and the effect of dipstick proteinuria on the cut-off value (CO) and accuracy of uPCR are unclear.

METHODS

The subjects included Japanese patients ≥ 18 years old with lifestyle-related diseases who had an estimated glomerular filtration rate of ≥ 15 ml/min/1.73 m² and uPCR of < 0.5 g/gCr at initiation. Urine dipstick, uPCR and urine albumin-to-creatinine ratio (uACR) were measured three times per case. Microalbuminuria was defined as uACR of 30-299 mg/gCr for at least 2 of 3 measurements. Youden's Index was used as the optimal CO. Factors associated with microalbuminuria were analyzed using a logistic regression model.

RESULTS

In 313 non-diabetic cases (median 70.8 years old), 3 dipstick proteinuria measurements were independently useful for detecting microalbuminuria, and the CO was set when a trace finding was obtained at least 1 of 3 times (sensitivity 0.56, specificity 0.80, positive predictive value [PPV] 0.73, negative predictive value [NPV] 0.65). A single uPCR measurement was more useful than 3 dipstick measurements, and was useful for detecting microalbuminuria even in cases with three consecutive negative proteinuria findings, indicating that the CO of the second uPCR with G1-3a (n = 136) was 0.06 g/gCr (sensitivity 0.76, specificity 0.84. PPV 0.68, NPV 0.89), while that with G3-b4 (n = 59) was 0.10 g/gCr (sensitivity 0.56, specificity 0.91. PPV 0.83, NPV 0.71). The sum of 3 uPCRs was useful for detecting microalbuminuria in cases with G1-3a (sensitivity 0.67, specificity 0.94, PPV 0.82, NPV 0.86) and G3b-4 (sensitivity 0.78, specificity 0.94, PPV 0.91 NPV 0.83), with both COs being 0.23 g/gCr. These COs of microalbuminuria did not change when trace or more proteinuria was included, although the sensitivity increased. A high uPCR and low urine specific gravity or creatinine level were independent factors for uACR ≥ 30 mg/gCr in cases with negative proteinuria, although the uPCR was a major predictive factor of a uACR ≥ 30 mg/gCr.

CONCLUSIONS

The uPCR (preferably determined using early-morning urine), including in dipstick-negative proteinuria cases with non-diabetic lifestyle-related diseases, can aid in the early detection of microalbuminuria.

TRIAL REGISTRATION

Retrospectively registered.

Glomerular filtration rate by different measures and albuminuria are associated with risk of frailty: the Rugao Longitudinal Ageing Study

BACKGROUND AND AIM

A decreased estimated glomerular filtration rate (eGFR) is associated with frailty, but the association between kidney function and frailty using multidimensional assessments has not been entirely examined. We aimed to investigate whether albuminuria and the eGFR using different biomarkers were associated with frailty.

METHODS

A total of 1830 older adults were included. Kidney function was assessed by the eGFR (based on combined creatinine-cystatin C [eGFR_cr-cys]) and β₂-microglobulin [eGFR_B2M]) and urine albumin-creatinine ratio (UACR). Frailty was measured by the Fried phenotype (FP) and frailty index (FI). Logistic regression models were used to investigate cross-sectional and longitudinal associations of baseline kidney measures with prevalent and incident frailty.

RESULTS

At baseline, kidney function was associated with prevalent frailty. During the 2-year follow-up, a decreased eGFR (per 10 units) was associated with an increased risk of incident frailty using the FP (eGFR_cr-cys: OR 1.18, 95% CI 1.03-1.35; eGFR_B2M: OR 1.14, 95% CI 1.02-1.29, respectively) and FI (eGFR_B2M: OR 1.18, 95% CI 1.04-1.65). An increased logUACR was associated with a higher risk of incident frailty using the FP (OR 1.18, 95% CI 1.03-1.35). Additionally, individuals with chronic kidney disease (CKD) had a higher risk of incident frailty using the FP (eGFR_cr-cys: OR 2.13, 95% CI 1.28-3.47; eGFR_B2M: OR 1.58, 95% CI 1.10-2.29, respectively) and FI (eGFR_cr-cys: OR 1.97, 95% CI 1.15-3.32; eGFR_B2M: OR 1.51, 95% CI 1.03-2.24, respectively).

CONCLUSION

Kidney function decline and CKD were associated with an increased risk of prevalent and incident frailty in older adults. Physicians should pay more attention to monitoring frailty status in older adults with CKD, even in those with kidney function decline.

An expert consensus on practical clinical recommendations and guidance for patients with classic Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder that causes accumulation of glycosphingolipids in body fluids and tissues, leading to progressive organ damage and reduced life expectancy. It can affect both males and females and can be classified into classic or later-onset phenotypes. In classic Fabry disease, α-galactosidase A (α-Gal A) activity is absent or severely reduced and disease manifestations have an early onset that can affect multiple organs. In contrast, in later-onset Fabry disease, patients have residual α-Gal A activity and clinical features are primarily confined to the heart. Individualized therapeutic goals in Fabry disease are required due to varying phenotypes and patient characteristics, and the wide spectrum of disease severity. An international group of expert physicians convened to discuss and develop practical clinical recommendations for disease- and organ-specific therapeutic goals in Fabry disease, based on expert consensus and evidence identified through a structured literature review. Biomarkers reflecting involvement of various organs in adult patients with classic Fabry disease are discussed and consensus recommendations for disease- and organ-specific therapeutic goals are provided. These consensus recommendations should support the establishment of individualized approaches to the management of patients with classic Fabry disease by considering identification, diagnosis, and initiation of disease-specific therapies before significant organ involvement, as well as routine monitoring, to reduce morbidity, optimize patient care, and improve patient health-related quality of life.

Interleukin (IL) 16: a candidate urinary biomarker for proliferative lupus nephritis

Objective

Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE). The pathogenesis is incompletely understood and diagnostic biomarkers are scarce. We investigated interleukin (IL) 16 as a potential biomarker for LN in a well-characterised cohort of patients with SLE.

Methods

We measured urinary (u-) and plasma (p-) levels of IL-16 in predefined patient groups using ELISA: LN (n=84), active non-renal SLE (n=63), inactive non-renal SLE (n=73) and matched population controls (n=48). The LN group included patients with recent biopsy-confirmed proliferative (PLN, n=47), mesangioproliferative (MES, n=11) and membranous (MLN, n=26) LN. Renal expression of IL-16 was investigated by immunohistochemistry. Associations between IL-16 measurements and clinical parameters and the diagnostic value for LN were explored.

Results

p-IL-16 was detected in all investigated cases and high p-IL-16 levels were observed in patients with active SLE. u-IL-16 was detected (dt-u-IL-16) in 47.6% of patients with LN, while only up to 17.8% had dt-u-IL-16 in other groups. In the LN group, 68% of patients with PLN had dt-u-IL-16, while the proportions in the MLN and MES groups were lower (11.5% and 45.5%, respectively). The highest u-IL-16 levels were detected in the PLN group. In the regression model, u-IL-16 levels differentiated PLN from other LN patient subgroups (area under the curve 0.775–0.896, p<0.0001). dt-u-IL-16 had superior specificity but slightly lower sensitivity than elevated anti-double-stranded DNA and low complement C3 or C4 in diagnosing PLN. A high proportion of LN kidney infiltrating cells expressed IL-16.

Conclusions

We demonstrate that detectable u-IL-16 can differentiate patients with PLN from those with less severe LN subtypes and active non-renal SLE. Our findings suggest that u-IL-16 could be used as a screening tool at suspicion of severe LN. Furthermore, the high IL-16 levels in plasma, urine and kidney tissue imply that IL-16 could be explored as a therapeutic target in SLE.

Exploring mHealth potential to improve kidney function: secondary analysis of a randomized trial of diabetes self-care in diverse adults

BACKGROUND

Many individuals living with chronic kidney disease (CKD) have comorbid Type 2 diabetes (T2D). We sought to explore if efficacious interventions that improve glycemic control may also have potential to reduce CKD progression.

METHODS

REACH is a text message-delivered self-management support intervention, which focused on medication adherence, diet, and exercise that significantly improved glycemic control in N = 506 patients with T2D. Using data from the trial, we characterized kidney health in the full sample and explored the intervention's effect on change in estimated glomerular filtration rate (eGFR) at 12 months in a subsample of N=271 patients with eGFR data.

RESULTS

In a diverse sample with respect to race/ethnicity and socioeconomic status, 37.2% had presence of mild or heavy proteinuria and/or an eGFR < 60 mL/min/1.73 m². There was a trending interaction effect between intervention and presence of proteinuria at baseline (b = 6.016, p = .099) such that patients with proteinuria at baseline who received REACH had less worsening of eGFR.

CONCLUSIONS

Future research should examine whether diabetes directed self-management support reduces CKD progression in ethnically diverse individuals with albuminuria. In highly comorbid populations, such as T2D and CKD, text-based support can be further tailored according to individuals' multimorbid disease self-management needs and is readily scalable for individuals with limited resources.

TRIAL REGISTRATION

This study was registered with ClinicalTrials.gov ( NCT02409329 ).

Pre-eclampsia: a Scoping Review of Risk Factors and Suggestions for Future Research Direction

Abstract

Most of maternal deaths are preventable, and one-quarter of maternal deaths are due to pre-eclampsia and eclampsia. Prenatal screening is essential for detecting and managing pre-eclampsia. However, pre-eclampsia screening is solely based on maternal risk factors and has low (< 5% in the USA) detection rates. This review looks at pre-eclampsia from engineering, public health, and medical points of view. First, pre-eclampsia is defined clinically, and the biological basis of established risk factors is described. The multiple theories behind pre-eclampsia etiology should serve as the scientific basis behind established risk factors for pre-eclampsia; however, African American race does not have sufficient evidence as a risk factor. We then briefly describe predictive statistical models that have been created to improve screening detection rates, which use a combination of biophysical and biochemical biomarkers, as well as aspects of patient medical history as inputs. Lastly, technologies that aid in advancing pre-eclampsia screening worldwide are explored. The review concludes with suggestions for more robust pre-eclampsia research, which includes diversifying study sites, improving biomarker analytical tools, and for researchers to consider studying patients before they become pregnant to improve pre-eclampsia detection rates. Additionally, researchers must acknowledge the systemic racism involved in using race as a risk factor and include qualitative measures in study designs to capture the effects of racism on patients.

Lay Summary

Pre-eclampsia is a pregnancy-specific hypertensive disorder that can affect almost every organ system and complicates 2-8% of pregnancies globally. Here, we focus on the biological basis of the risk factors that have been identified for the condition. African American race currently does not have sufficient evidence as a risk factor and has been poorly studied. Current clinical methods poorly predict a patient's likelihood of developing pre-eclampsia; thus, researchers have made statistical models that are briefly described in this review. Then, low-cost technologies that aid in advancing pre-eclampsia screening are discussed. The review ends with suggestions for research direction to improve pre-eclampsia screening in all settings.Overall, we suggest that the future of pre-eclampsia screening should aim to identify those at risk before they become pregnant. We also suggest that the clinical standard of assessing patient risk solely on patient characteristics needs to be reevaluated, that study locations of pre-eclampsia research need to be expanded beyond a few high-income countries, and that low-cost technologies should be developed to increase access to prenatal screening.

Early Identification of Chronic Kidney Disease – A Scoping Review of the Global Populations

Introduction

Decisions on whether to screen for chronic kidney disease (CKD) or not remain contentious in nephrology. This study provides a global overview of early CKD identification efforts.

Methods

Guidelines for scoping reviews were followed and studies were identified by searching MEDLINE, EMBASE, Cochrane Library, CINAHL, ISI Web of Science, and PsycINFO. Data extracted from included studies focused on the following 4 themes: study population, measurement methods, interventions used, and available policies.

Results

We identified 290 CKD screening and detection programs from 83 countries. Overall sample size was 3.72 million (North East Asia: 1.19 million), detection of CKD was the aim in 97.6%, 63.1% used population-based screening methods, and only 12.4% were in rural populations. Reported CKD prevalence (stages 3–5) was higher in targeted- (14.8%) than population-based studies (8.0%). Number of persons needed to screen (NNS) to identify 1 case was also lower in targeted studies (7 vs. 13). Single measurements (80%) and the combination of estimation of glomerular filtration rate with a urine test (albuminuria/proteinuria) (71.4%) were frequently used to detect CKD. Only 2.8% of studies included an intervention such as pharmacotherapy in identified cases. Policies on early identification were available in 30.1% of countries included.

Conclusion

Methods for early CKD identification vary worldwide, often leading to wide variations in the reported prevalence. Efforts to standardize measurement methods for early detection focusing on high-risk populations and ensuring appropriate interventions are available to those identified with CKD will improve the value of programs and improve patient outcomes.

Comparison of 24-h Urine Protein, Urine Albumin-to-Creatinine Ratio, and Protein-to-Creatinine Ratio in IgA Nephropathy

Background

Proteinuria is a strong risk factor for renal outcomes in IgA nephropathy. Random urine protein-to-creatinine ratio (PCR), random albumin-to-creatinine ratio (ACR), and 24-h urine protein excretion (24-h UP) have been widely used in clinical practice. However, the measurement which is the best predictor of long-term renal outcomes remains controversial. This study aimed to compare the three measurements in IgA nephropathy.

Methods

We conducted a retrospective study of 766 patients with IgA nephropathy. The associations among baseline ACR, PCR, and 24-h UP with chronic kidney disease (CKD) progression event, defined as 50% estimated glomerular filtration rate (eGFR) decline or end stage kidney disease (ESKD), were tested and compared.

Results

In this study, ACR, PCR, and 24-h UP showed high correlation (r = 0.671-0.847, P < 0.001). After a median follow-up of 29.88 (14.65-51.65) months, 51 (6.66%) patients reached the CKD progression event. In univariate analysis, ACR performed better in predicting the prognosis of IgA nephropathy, with a higher area under the receiver operating curve (ROC) curve than PCR and 24-h UP. After adjustment for traditional risk factors, ACR was most associated with composite CKD progression event [per log-transformed ACR, hazard ratio (HR): 2.82; 95% (95% CI): 1.31-6.08; P = 0.008].

Conclusions

In IgA nephropathy, ACR, PCR, and 24-h UP had a high correlation. ACR performed better in predicting the prognosis of IgA nephropathy.

96DRA-urine: A high throughput sample preparation method for urinary proteome analysis

Mass spectrometry (MS)-based urinary proteomics is increasingly used for clinical research. A critical step in urinary proteomic analysis comprises the implementation of a reliable sample preparation method with high yields of peptides and proteins. In this study, we developed a urinary sample preparation method, DRA-Urine (Direct reduction/alkylation in urine), which urinary proteins were directly reduced/alkylated in urine, and then precipitated by acetone, washed and digestion on an ultrafilter unit. The qualitative and quantitative comparison of different urinary sample preparation methods (in-solution methods and ultrafilter-assisted methods) showed that DRA-Urine could achieve better results. Adapting DRA-Urine protocol to a 96-well format, namely 96DRA-Urine, shortened the time for buffer change and improved sample preparation throughput. The results showed that 96DRA-Urine displayed similar proteomic performance to DRA-Urine. Finally, the 96DRA-Urine method was used in a label-free, small pilot biomarker discovery analysis for differential urinary proteome analysis of bladder cancer urine. The results showed that urinary proteins could differentiate bladder cancer (BCa) patients from healthy controls and distinguish high-grade BCa from low-grade BCa with area under the curve (AUC) values of 0.972 and 0.847, respectively. Consequently, the 96DRA-Urine method might be a high-throughput method for preparing body fluid samples used in clinical research but needs to be further verified.

Prospective urinary albumin/creatinine ratio for diagnosis, staging, and organ response assessment in renal AL amyloidosis: results from a large cohort of patients

OBJECTIVES

Quantification of 24 h-proteinuria is the gold standard for diagnosing, staging, and monitoring of patients with renal AL amyloidosis. However, 24 h-urine collection is cumbersome and may result in preanalytical error. In this prospective study, we investigated the role of urinary albumin/creatinine ratio (UACR) (cut-off: 300 mg/g) identifying renal involvement, evaluated a UACR-based staging system (UACR cut-off: 3,600 mg/g) and assessed whether UACR response (UACR decrease >30% without worsening in eGFR >25%) predicts renal outcome in 531 patients with newly-diagnosed AL amyloidosis.

METHODS

From October 2013 paired 24 h-proteinuria and UACR (on first morning void) were measured in all newly-diagnosed patients with AL amyloidosis. Correlation between 24 h-proteinuria and UACR at baseline was assessed by Pearson's r test. Impact of UACR response on renal outcome was assessed in randomly created testing (n=354) and validation (n=177) cohorts.

RESULTS

A strong linear correlation was found between 24 h-proteinuria and UACR at baseline (r=0.90; p<0.001). After a median follow-up of 31 months, 57 (11%) patients required dialysis. A UACR-based renal staging system identified three stages with significantly higher dialysis rate at 36 months comparing stage I with stage II and stage II with stage III. Achieving a renal response, according to a UACR-based criterion, resulted in lower dialysis rate in both testing and validation cohorts.

CONCLUSIONS

UACR is a reliable marker for diagnosis, prognosis, and organ response assessment in renal AL amyloidosis and can reliably replace 24 h-proteinuria in clinical trials and individual patients' management.

Smartphone-Assisted Protein to Creatinine Ratio Determination on a Single Paper-Based Analytical Device

Proteinuria is a condition in which an excessive amount of protein is excreted in urine. It is, among others, an indicator of kidney disease or risk of cardiovascular disease. Rapid and reliable diagnosis and monitoring of proteinuria is of great importance for both patients and their physicians. For that reason, a paper-based sensor for proteinuria diagnosis was designed, optimized, and validated utilizing smartphone-assisted signal acquisition. In the first step, a few commonly employed protein assays were optimized and compared in terms of analytical performance on paper matrix. The tetrabromophenol blue method was selected as the one providing a sufficiently low limit of detection (39 mg·L-1) on the one hand and appropriate long-term stability (up to 3 months) on the other hand. The optimized assay was employed for protein-to-creatinine ratio (PCR) determination on a single paper-based sensor. For both analytes the linear ranges were within the clinically relevant range. The analytical usefulness of the developed sensors was demonstrated by a PCR recovery study in artificial urine. The obtained PCR recoveries were from ca. 80 to 150%.

Chronic kidney disease measures for cardiovascular risk prediction

Chronic kidney disease (CKD) affects 15-20% of adults globally and causes various complications, one of the most important being cardiovascular disease (CVD). CKD has been associated with many CVD subtypes, especially severe ones like heart failure, independent of potential confounders such as diabetes and hypertension. There is no consensus in major clinical guidelines as to how to incorporate the two key measures of CKD (glomerular filtration rate and albuminuria) for CVD risk prediction. This is a critical missed opportunity to appropriately refine predicted risk and personalize prevention therapies according to CKD status, particularly since these measures are often already evaluated in clinical care. In this review, we provide an overview of CKD definition and staging, the subtypes of CVD most associated with CKD, major pathophysiological mechanisms, and the current state of CKD as a predictor of CVD in major clinical guidelines. We will introduce the novel concept of a "CKD Add-on", which allows the incorporation of CKD measures in existing risk prediction models, and the implications of taking into account CKD in the management of CVD risk.

A miniaturized optoelectronic biosensor for real-time point-of-care total protein analysis

A miniaturized optoelectronic sensor is demonstrated that measures total protein concentration in serum and urine with sensitivity and accuracy comparable to gold-standard methods. The sensor is comprised of a vertical cavity surface emitting laser (VCSEL), photodetector and other custom optical components and electronics that can be hybrid packaged into a portable, handheld form factor. In conjunction, a custom fluorescence assay has been developed based on the protein-induced fluorescence enhancement (PIFE) phenomenon, enabling real-time sensor response to changes in protein concentration. Methods are described for the following:•

Standard curves: Used to determine the sensitivity, dynamic range, and linearity of the VCSEL biosensor/PIFE assay system in buffer as well as in human blood and urine samples.

•

Comparison of VCSEL biosensor performance with a benchtop fluorimetric microplate reader.

•

Accuracy of the VCSEL biosensor/PIFE assay system: Evaluated by comparing sensor measurements with gold-standard clinical laboratory measurements of total protein in serum and urine samples from patients with diabetes.

Derivation and External Validation of a Risk Index for Predicting Acute Kidney Injury Requiring Kidney Replacement Therapy After Noncardiac Surgery

IMPORTANCE

Severe acute kidney injury (AKI) is a serious postoperative complication. A tool for predicting the risk of AKI requiring kidney replacement therapy (KRT) after major noncardiac surgery might assist with patient counseling and targeted use of measures to reduce this risk.

OBJECTIVE

To derive and validate a predictive model for AKI requiring KRT after major noncardiac surgery.

DESIGN, SETTING, AND PARTICIPANTS

In this prognostic study, 5 risk prediction models were derived and internally validated in a population-based cohort of adults without preexisting kidney failure who underwent noncardiac surgery in Alberta, Canada, between January 1, 2004, and December 31, 2013. The best performing model and corresponding risk index were externally validated in a population-based cohort of adults without preexisting kidney failure who underwent noncardiac surgery in Ontario, Canada, between January 1, 2007, and December 31, 2017. Data analysis was conducted from September 1, 2019, to May 31, 2021.

EXPOSURES

Demographic characteristics, surgery type, laboratory measures, and comorbidities before surgery.

MAIN OUTCOMES AND MEASURES

Acute kidney injury requiring KRT within 14 days after surgery. Discrimination was assessed using the C statistic; calibration was assessed using calibration intercept and slope. Logistic recalibration was used to optimize model calibration in the external validation cohort.

RESULTS

The derivation cohort included 92 114 patients (52.2% female; mean [SD] age, 62.3 [18.0] years), and the external validation cohort included 709 086 patients (50.8% female; mean [SD] age, 61.0 [16.0] years). A total of 529 patients (0.6%) developed postoperative AKI requiring KRT in the derivation cohort, and 2956 (0.4%) developed postoperative AKI requiring KRT in the external validation cohort. The following factors were consistently associated with the risk of AKI requiring KRT: younger age (40-69 years: odds ratio [OR], 2.07 [95% CI, 1.69-2.53]; <40 years: OR, 3.73 [95% CI, 2.61-5.33]), male sex (OR, 1.55; 95% CI, 1.28-1.87), surgery type (colorectal: OR, 4.86 [95% CI, 3.28-7.18]; liver or pancreatic: OR, 6.46 [95% CI, 3.85-10.83]; other abdominal: OR, 2.19 [95% CI, 1.66-2.89]; abdominal aortic aneurysm repair: OR, 19.34 [95% CI, 14.31-26.14]; other vascular: OR, 7.30 [95% CI, 5.48-9.73]; thoracic: OR, 3.41 [95% CI, 2.07-5.59]), lower estimated glomerular filtration rate (OR, 0.97; 95% CI, 0.97-0.97 per 1 mL/min/1.73 m2 increase), lower hemoglobin concentration (OR, 0.99; 95% CI, 0.98-0.99 per 0.1 g/dL increase), albuminuria (mild: OR, 1.88 [95% CI, 1.52-2.33]; heavy: OR, 3.74 [95% CI, 2.98-4.69]), history of myocardial infarction (OR, 1.63; 95% CI, 1.32-2.03), and liver disease (mild: OR, 2.32 [95% CI, 1.66-3.24]; moderate or severe: OR, 4.96 [95% CI, 3.58-6.85]). In external validation, a final model including these variables showed excellent discrimination (C statistic, 0.95; 95% CI, 0.95-0.96), with sensitivity of 21.2%, specificity of 99.9%, positive predictive value of 38.1%, and negative predictive value of 99.7% at a predicted risk threshold of 10% or greater.

CONCLUSIONS AND RELEVANCE

The findings suggest that this risk model can predict AKI requiring KRT after noncardiac surgery using routine preoperative data. The model may be feasible for implementation in clinical perioperative risk stratification for severe AKI.

New Possibilities in Quantitative Assessment of Albuminuria in Patients with Atrial Fibrillation and Chronic Kidney Disease

Aim. To evaluate the relationship between albumin to creatinine ratio (ACR) in a single and 24-hours urine spots and chronic kidney disease (CKD) progression pace in patients with atrial fibrillation, CKD and diabetes mellitus.

Material and methods. 60 patients with atrial fibrillation (AF) and CKD were enrolled, study duration was 15 months. The patients were divided into two groups depending on the presence of DM. Total number of ACR tests was 170, dynamics of CKD progression was estimated with CKD-EPI formula for first visit and 15th month’s follow-up.

Results. The median score of CHA2DS2VASс scale was 4 [3;5]. The risk of hemorrhagic complications in both groups was low (median score 1 [1;1]. There is a strong statistically significant correlation between ACR in a single and 24-hours urine spots (p<0.001). No significant changes in kidney function within 15 months were found (GFR 53 [46;59] ml/min/1.73 m2 vs 50.5 [45.63] ml/min/1.73 m2 for patients with diabetes mellitus [DM] [p=0.94] and GFR 52.5 [46.58] ml/min/1.73 m2 vs 50 [44.58] ml/min/1.73 m2 for patients without DM [p=0.711]). When comparing the renal function of patients with and without DM after 15 months statistically significant differences were also not found (p = 0.510).

Conclusion. In respect that assessment of single sample ACR is much more practical and reliable, this method might replace traditional 24-hours urine assessment in future. However, due to the small sample size and the presence of wide discrepancies in individual cases, which can be associated with preanalytical errors in urine collection, large randomized clinical trials are needed to confirm the obtained data.

Clinicopathologic Features and Risk Factors of Proteinuria in Transplant Glomerulopathy

Background: Transplant glomerulopathy (TG) is one of the main causes of post-transplant proteinuria (PU). The features and possible risk factors for proteinuria in TG patients are uncertain.

Methods: We investigated all patients who had biopsy-proven TG from 2000 to 2018 in our center. The clinical and histological data were compared between two groups with or without PU (cut-off = 0.3 g/day). Spearman correlation analysis was used to evaluate the relationship between PU and pathological changes. The risk factors for PU in TG patients were determined by multivariable logistic regression analysis.

Results: One hundred and twenty-five (75.76%) of all enrolled 165 TG patients had proteinuria ≥0.3 g/day at the time of biopsy. TG patients' PU level was significantly correlated with Banff lesion score cg (ρ = 0.247, P = 0.003), and mm (ρ = 0.257, P = 0.012). Systolic blood pressure ≥140 mmHg (OR 2.72, 95% CI 1.04–7.10, P = 0.041), diastolic blood pressure ≥90 mmHg (OR 4.84, 95% CI 1.39–16.82, P = 0.013), peak PRA ≥5% (OR 6.47, 95% CI 1.67–25.01, P = 0.007), positive C4d staining (OR 4.55, 95% CI 1.29–16.11, 0.019), tacrolimus-based regimen (OR 3.5, 95% CI 1.28–9.54, P = 0.014), and calcium channel blocker usage (OR 4.38, 95% CI 1.59–12.09, P = 0.004) were independent risk factors for PU.

Conclusions: Proteinuria is common in TG patients. systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, peak PRA ≥5%, positive C4d staining, tacrolimus-based regimen, and calcium channel blocker usage are associated with proteinuria in TG patients.

Real-time point-of-care total protein measurement with a miniaturized optoelectronic biosensor and fast fluorescence-based assay

Measurement of total protein in urine is key to monitoring kidney health in diabetes. However, most total protein assays are performed using large, expensive laboratory chemistry analyzers that are not amenable to point-of-care analysis or home monitoring and cannot provide real-time readouts. We developed a miniaturized optoelectronic biosensor using a vertical cavity surface-emitting laser (VCSEL), coupled with a fast protein assay based on protein-induced fluorescence enhancement (PIFE), that can dynamically measure protein concentrations in protein-spiked buffer, serum, and urine in seconds with excellent sensitivity (urine LOD = 0.023 g/L, LOQ = 0.075 g/L) and over a broad range of physiologically relevant concentrations. Comparison with gold standard clinical assays and standard fluorimetry tools showed that the sensor can accurately and reliably quantitate total protein in clinical urine samples from patients with diabetes. Our VCSEL biosensor is amenable to integration with miniaturized electronics, which could afford a portable, low-cost, easy-to-use device for sensitive, accurate, and real-time total protein measurements from small biofluid volumes.

Brief Report: Subclinical Kidney Dysfunction in HIV-Infected Children: A Cross-Sectional Study

OBJECTIVE

Most of the kidney dysfunction in HIV-positive children receiving antiretroviral therapy (ART) is attributed to tenofovir. There is a paucity of data on kidney dysfunction in tenofovir-naive children. The primary objective was to know the point prevalence of albuminuria and β2-microglobulinuria in HIV-infected children aged 3-18 years receiving ART. Albuminuria and β2-microglobulinuria were used as surrogates for glomerular and tubular dysfunction, respectively. The secondary objective was to determine their predictors.

DESIGN

Cross-sectional study-design.

METHODS

One hundred consecutive HIV-positive children (3-18 years) on ART were included. Spot urine sample was analyzed for urinary creatinine, total protein, microalbumin, and β2-microglobulin. Albuminuria was defined as albumin to creatinine ratio of >30 mg/g; proteinuria as urine dipstick ≥trace or spot urine protein to creatinine ratio (uPCR) of ≥0.2. β2-microglobulinuria was defined as β2-microglobulin levels of >350 µg/L.

RESULTS

There were 71 boys and 29 girls. Most of the children had WHO clinical stage I and were getting zidovudine-based regimen. Only 7 children were getting tenofovir. estimated Glomerular Filtration Rate and serum creatinine were normal in all children. Approximately half (48%) had renal dysfunction in the form of glomerular dysfunction (26%), tubular dysfunction (27%), or both (5%). Age at diagnosis was significantly associated with β2-microglobulinuria (P = 0.044). None of the selected variables were associated with albuminuria.

CONCLUSIONS

HIV-associated glomerular and tubular dysfunction is common in children receiving ART other than tenofovir. The standard guidelines should consider including routine urinary biomarker monitoring in children on ART.

Prediction of microalbuminuria from proteinuria in chronic kidney disease due to non-diabetic lifestyle-related diseases: comparison with diabetes

BACKGROUND

To suppress increases in kidney failure and cardiovascular disease due to lifestyle-related diseases other than diabetes, early intervention is desirable. We examined whether microalbuminuria could be predicted from proteinuria.

METHODS

The participants consisted of adults who exhibited a urinary protein-to-creatinine ratio (uPCR) of < 0.5 g/gCr and an eGFR of ≥ 15 ml/min/1.73 m² in their spot urine at their first examination for lifestyle-related disease. Urine was tested three times for each case, with microalbuminuria defined as a urinary albumin-to-creatinine ratio (uACR) of 30-299 mg/gCr, at least twice on three measurements. Youden's Index was used as an index of the cut-off value (CO) according to the ROC curve.

RESULTS

A single uPCR was useful for differentiating normoalbuminuria and micro- and macroalbuminuria in patients with non-diabetic lifestyle-related diseases. Regarding the GFR categories, the CO of the second uPCR was 0.09 g/gCr (AUC 0.89, sensitivity 0.76, specificity 0.89) in G1-4 (n = 197) and 0.07 g/gCr (AUC 0.92, sensitivity 0.85, specificity 0.88) in G1-3a (n = 125). Using the sum of two or three uPCR measurements was more useful than a single uPCR for differentiating microalbuminuria in non-diabetic lifestyle disease [CO, 0.16 g/gCr (AUC 0.91, sensitivity 0.85, specificity 0.87) and 0.23 g/gCr (AUC 0.92, sensitivity 0.88, specificity 0.84), respectively].

CONCLUSION

Microalbuminuria in Japanese individuals with non-diabetic lifestyle-related diseases can be predicted from the uPCR, wherein the CO of the uPCR that differentiates normoalbuminuria and micro- and macroalbuminuria was 0.07 g/gCr for G1-3a, while that in G3b-4 was 0.09 g/gCr.

The relationship between proteinuria and allograft survival in patients with transplant glomerulopathy: a retrospective single-center cohort study

Proteinuria and transplant glomerulopathy (TG) are common in kidney transplantation. To date, there is limited knowledge regarding proteinuria in different types of TG and its relationship to allograft survival. A retrospective cohort analysis of TG patients from indication biopsies was performed to investigate the relationship of proteinuria, histology, and graft survival. One hundred and seven (57.5%) out of 186 TG patients lost their grafts with a median survival of 14 [95% confidence interval (CI) 10-22] months after diagnosis. Proteinuria ≥1 g/24 h at the time of biopsy was detected in 87 patients (46.8%) and the median of proteinuria was 0.89 (range 0.05-6.90) g/24 h. TG patients with proteinuria ≥1 g/24 h had worse 5-year graft survival (29.9% vs. 53.5%, P = 0.001) compared with proteinuria <1 g/24 h. Proteinuria was associated with graft loss in univariable Cox regression [hazard ratio (HR) 1.25, 95% CI, 1.11-1.41, P < 0.001], and in multivariable analysis (adjusted HR 1.26, 95% CI 1.11-1.42, P < 0.001) independent of other risk factors including creatinine at biopsy, positive C4d, history of rejection, and Banff lesion score mesangial matrix expansion. In this cohort of TG patients, proteinuria at indication biopsy is common and associated with a higher proportion of graft loss.

Graft Function, Albuminuria, and the Risk of Hemorrhage and Thrombosis After Kidney Transplantation

Background:

Compared to the general population, kidney transplant recipients are at increased risk of hemorrhage and thrombosis. Whether this risk is affected by graft function and albuminuria is unknown.

Objective:

To determine the association between graft function and albuminuria and the risk of post-transplant hemorrhage and thrombosis.

Design:

Retrospective cohort study.

Setting:

We used linked health care databases in Alberta, Canada.

Patients/sample/participants:

We included adult kidney transplant recipients from 2002 to 2015 with a functioning graft at 1 year.

Measurements:

Estimated glomerular filtration rate (eGFR) and albuminuria measurements at 1 year post-transplant were used to categorize recipients (eGFR: ≥45 vs. <45 mL/min/1.73 m²; albuminuria: absence vs. presence). We determined the rates of post-transplant hemorrhage and venous thrombosis based on validated diagnostic and procedural codes.

Methods:

We determined the association between categories of eGFR and albuminuria and post-transplant hemorrhage and venous thrombosis using Poisson regression with log link.

Results:

Of 1284 kidney transplant recipients, 21% had an eGFR <45 mL/min/1.73 m² and 40% had presence of albuminuria at 1 year post-transplant. Over a median follow-up of 6 years, there were 100 hemorrhages (12.6 events per 1000 person-years) and 57 venous thrombosis events (7.1 events per 1000 person-years). The age- and sex-adjusted rate of hemorrhage and thrombosis was over 2-fold higher in recipients with lower eGFR and presence of albuminuria compared to higher eGFR and no albuminuria (hemorrhage: incidence rate ratio, IRR, 2.6, 95% confidence interval [CI]: 1.5-4.4, P = .001; thrombosis: IRR, 2.3, 95% CI: 1.1-5.0, P = .046).

Limitations:

Complete relevant medication information, such as anticoagulants, were not available in our datasets. Due to sample size, this study was underpowered to conduct a fully adjusted analysis.

Conclusion:

Among kidney transplant recipients, lower eGFR and presence of albuminuria at 1 year post-transplant were associated with an over 2-fold higher risk of hemorrhage and venous thrombosis. Graft function and albuminuria at 1 year post-transplant are important prognostic factors in determining risk of post-transplant hemorrhage and venous thrombosis. Further research, including medication data, are needed to further delineate outcomes and safety.

Trial registration:

Not applicable (cohort study).

Conversion of Urine Protein-Creatinine Ratio or Urine Dipstick Protein to Urine Albumin-Creatinine Ratio for Use in Chronic Kidney Disease Screening and Prognosis : An Individual Participant-Based Meta-analysis

BACKGROUND

Although measuring albuminuria is the preferred method for defining and staging chronic kidney disease (CKD), total urine protein or dipstick protein is often measured instead.

OBJECTIVE

To develop equations for converting urine protein-creatinine ratio (PCR) and dipstick protein to urine albumin-creatinine ratio (ACR) and to test their diagnostic accuracy in CKD screening and staging.

DESIGN

Individual participant-based meta-analysis.

SETTING

12 research and 21 clinical cohorts.

PARTICIPANTS

919 383 adults with same-day measures of ACR and PCR or dipstick protein.

MEASUREMENTS

Equations to convert urine PCR and dipstick protein to ACR were developed and tested for purposes of CKD screening (ACR ≥30 mg/g) and staging (stage A2: ACR of 30 to 299 mg/g; stage A3: ACR ≥300 mg/g).

RESULTS

Median ACR was 14 mg/g (25th to 75th percentile of cohorts, 5 to 25 mg/g). The association between PCR and ACR was inconsistent for PCR values less than 50 mg/g. For higher PCR values, the PCR conversion equations demonstrated moderate sensitivity (91%, 75%, and 87%) and specificity (87%, 89%, and 98%) for screening (ACR >30 mg/g) and classification into stages A2 and A3, respectively. Urine dipstick categories of trace or greater, trace to +, and ++ for screening for ACR values greater than 30 mg/g and classification into stages A2 and A3, respectively, had moderate sensitivity (62%, 36%, and 78%) and high specificity (88%, 88%, and 98%). For individual risk prediction, the estimated 2-year 4-variable kidney failure risk equation using predicted ACR from PCR had discrimination similar to that of using observed ACR.

LIMITATION

Diverse methods of ACR and PCR quantification were used; measurements were not always performed in the same urine sample.

CONCLUSION

Urine ACR is the preferred measure of albuminuria; however, if ACR is not available, predicted ACR from PCR or urine dipstick protein may help in CKD screening, staging, and prognosis.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases and National Kidney Foundation.

Clinical significance of single and persistent elevation of serum high-sensitivity C-reactive protein levels for prediction of kidney outcomes in patients with impaired fasting glucose or diabetes mellitus

BACKGROUND

The association between high-sensitivity C-reactive protein (hs-CRP) and chronic kidney disease remains controversial and long-term longitudinal studies are limited. We aim to investigate the impact of single and persistent elevation of hs-CRP on kidney outcomes.

METHODS

Our study was based on a subgroup of patients with hyperglycemia from the Kailuan cohort. Patients were divided into three groups according to two consecutive hs-CRP levels: (1) no elevation (twice hs-CRP < 3 mg/L); (2) single elevation (once hs-CRP ≥ 3 mg/L); (3) persistent elevation (twice hs-CRP ≥ 3 mg/L). Kidney outcomes include kidney function decline (glomerular filtration rate [GFR] decline ≥ 30% within two years or doubling of serum c reatinine or development of end stage kidney disease [ESKD]), development and progression of proteinuria.

RESULTS

Regarding the outcomes of kidney function decline, development and progression of proteinuria, we included 18,665, 11,754 and 1710 patients into analyses, respectively. After 5 years of follow-up, the number of incident cases of kidney function decline, development and progression of proteinuria were 1891, 1337 and 171, respectively. Compared to patients with no elevation of hs-CRP levels, those with persistent but not single elevation of hs-CRP were at higher risk of kidney function decline (hazard ratio [HR] 1.42, 95% confidence interval [CI] 1.23-1.64) and development of proteinuria (1.49, 1.26-1.76), but not progression of proteinuria. The results were consistent with propensity score analysis.

CONCLUSION

Persistent but not single elevation of hs-CRP was independently associated with increased risk of kidney function decline, and development of proteinuria but not progression in patients with impaired fasting glucose or diabetes.

Early Detection of CKD: Implications for Low-Income, Middle-Income, and High-Income Countries

CKD is common, costly, and associated with adverse health outcomes. Because inexpensive treatments can slow the rate of kidney function loss, and because CKD is asymptomatic until its later stages, the idea of early detection of CKD to improve outcomes ignites enthusiasm, especially in low- and middle-income countries where renal replacement is often unavailable or unaffordable. Available data and prior experience suggest that the benefits of population-based screening for CKD are uncertain; that there is potential for harms; that screening is not a wise use of resources, even in high-income countries; and that screening has substantial opportunity costs in low- and middle-income countries that offset its hypothesized benefits. In contrast, some of the factors that diminish the value of population-based screening (such as markedly higher prevalence of CKD in people with diabetes, hypertension, and cardiovascular disease, as well as high preexisting use of kidney testing in such patients) substantially increase the appeal of searching for CKD in people with known kidney risk factors (case finding) in high-income countries as well as in low- and middle-income countries. For both screening and case finding, detection of new cases is the easiest component; the real challenge is ensuring appropriate management for a chronic disease, usually for years or even decades. This review compares and contrasts the benefits, harms, and opportunity costs associated with these two approaches to early detection of CKD. We also suggest criteria (discussed separately for high-income countries and for low- and middle-income countries) to use in assessing when countries should consider case finding versus when they should consider foregoing systematic attempts at early detection and focus on management of known cases.

Trace Proteinuria and the Incidence of Overt Proteinuria After Five Years: Results of the Kanagawa Investigation of the Total Checkup Data From the National Database-5 (KITCHEN-5)

Background

Trace proteinuria (TrP), which is usually defined as ± by dipstick urinalysis, is considered as normal and of limited clinical significance. However, the relationship between TrP and overt proteinuria (OP) (≥ +1) in the future is unknown. Therefore, we investigated the association between TrP and future incidence of OP in a community-based cohort study.

Methods

TrP detected during the initial 2 years, which was classified into transient TrP (once/2 years) (T-TrP) and recurrent TrP (twice/2 years) (R-TrP); and the incidence of OP after 5 years were investigated in 292,257 general Japanese people aged 40 - 68 years who attended checkups. To determine TrP and OP, dipstick urinalysis was conducted with visual reading (VR) by medical staff or automated reading (AR) using a machine reader.

Results

Overall, T-TrP and R-TrP were observed in 24,782 (8.5%) and 3,767 (1.3%) subjects, respectively. Both types of TrP were prevalent in the detection with AR than VR. The prevalences of T-TrP and R-TrP showed J-shaped relationships against baseline body mass index (BMI), regardless of sex and BMI categories. The incident of OP after 5 years was larger (around 10%) in R-TrP than T-TrP (around 5%): approximately two times. Logistic regression analysis showed that T-TrP and R-TrP were significantly associated with OP, even after adjustment for relevant confounding factors including age, sex, and BMI (odds ratios (95% confidence intervals (CIs)): 2.77 (2.60 - 2.95) and 4.85 (4.34 - 5.43)), which were not largely altered when sub-analysis was conducted according to men and women, non-obesity and obesity, or AR and VR. In all analysis above, the odds ratios (95% CIs) of R-TrP for OP were higher than T-TrP.

Conclusions

Our findings suggest that TrP, particularly R-TrP, is substantially associated with the future incidence of OP, which may be independent of confounding factors and the methods detecting TrP.

Clinical update: The important role of dual kidney function testing (ACR and eGFR) in primary care: Identification of risk and management in type 2 diabetes

Diabetic kidney disease (DKD) is common complication of type 1 and type 2 diabetes and may lead to progressive kidney dysfunction culminating in end-stage kidney disease. Kidney function is evaluated less frequently than other care procedures in patients with diabetes, even though the opportunity to identify DKD early and slow or even halt renal damage early in the disease progression represents a potentially important clinical opportunity for early intervention. The following review provides an overview of the under-recognised importance of kidney function in T2D and current best-practice to support the identification of DKD as part of primary care T2D management.

An independent validation of the kidney failure risk equation in an Asian population

Predicting the risk of end-stage renal disease (ESRD) progression facilitates appropriate nephrology care of patients with chronic kidney disease (CKD). Previously, the kidney failure risk equations (KFREs) were developed and validated in several cohorts. The purpose of this study is to validate the KFREs in a Korean population and to recalibrate the equations. A total of 38,905 adult patients, including 13,244 patients with CKD stages G3–G5, who were referred to nephrology were recruited. Using the original KFREs (4-, 6- and 8-variable equations) and recalibration equations, we predicted the risk of 2- and 5-year ESRD progression. All analyses were conducted in CKD stages G3-G5 patients as well as the total population. In CKD stages G3–G5 patients, All the original 4-, 6- and 8-variable equations showed excellent areas under the receiver operating characteristic curve of 0.87 and 0.83 for the 2- and 5-year risk of ESRD, respectively. The results of net reclassification improvement, integrated discrimination index and Brier score showed that recalibration improved the prediction models in some cases. The original KFREs showed high discrimination in both CKD stages G3–G5 patients and the total population referred to nephrology in this large Korean cohort. KFREs can be implemented in Korean health systems and can guide nephrology referrals and other CKD-related treatment decisions.

Proteomics-Based Machine Learning Approach as an Alternative to Conventional Biomarkers for Differential Diagnosis of Chronic Kidney Diseases

Diabetic nephropathy, hypertension, and glomerulonephritis are the most common causes of chronic kidney diseases (CKD). Since CKD of various origins may not become apparent until kidney function is significantly impaired, a differential diagnosis and an appropriate treatment are needed at the very early stages. Conventional biomarkers may not have sufficient separation capabilities, while a full-proteomic approach may be used for these purposes. In the current study, several machine learning algorithms were examined for the differential diagnosis of CKD of three origins. The tested dataset was based on whole proteomic data obtained after the mass spectrometric analysis of plasma and urine samples of 34 CKD patients and the use of label-free quantification approach. The k-nearest-neighbors algorithm showed the possibility of separation of a healthy group from renal patients in general by proteomics data of plasma with high confidence (97.8%). This algorithm has also be proven to be the best of the three tested for distinguishing the groups of patients with diabetic nephropathy and glomerulonephritis according to proteomics data of plasma (96.3% of correct decisions). The group of hypertensive nephropathy could not be reliably separated according to plasma data, whereas analysis of entire proteomics data of urine did not allow differentiating the three diseases. Nevertheless, the group of hypertensive nephropathy was reliably separated from all other renal patients using the k-nearest-neighbors classifier “one against all” with 100% of accuracy by urine proteome data. The tested algorithms show good abilities to differentiate the various groups across proteomic data sets, which may help to avoid invasive intervention for the verification of the glomerulonephritis subtypes, as well as to differentiate hypertensive and diabetic nephropathy in the early stages based not on individual biomarkers, but on the whole proteomic composition of urine and blood.