Urinary non-albumin protein-creatinine ratio is an independent predictor of mortality in patients with type 2 diabetes: a retrospective cohort study.

Albuminuria is a well-known predictor of chronic kidney disease in patients with type 2 diabetes mellitus (DM). However, proteinuria is associated with chronic complications in patients without albuminuria. In this retrospective cohort study, we explored whether non-albumin proteinuria is associated with all-cause mortality and compared the effects of non-albumin proteinuria on all-cause mortality between patients with and without albuminuria. We retrospectively collected data from patients with type 2 DM for whom we had obtained measurements of both urinary albumin-to-creatinine ratio (UACR) and urinary protein-to-creatinine ratio (UPCR) from the same spot urine specimen. Urinary non-albumin protein-creatinine ratio (UNAPCR) was defined as UPCR-UACR. Of the 1809 enrolled subjects, 695 (38.4%) patients died over a median follow-up of 6.4 years. The cohort was separated into four subgroups according to UACR (30 mg/g) and UNAPCR (120 mg/g) to examine whether these indices are associated with all-cause mortality. Compared with the low UACR and low UNAPCR subgroup as the reference group, multivariable Cox regression analyses indicated no significant difference in mortality in the high UACR and low UNAPCR subgroup (hazard ratio [HR] 1.189, 95% confidence interval [CI] 0.889-1.589, P = 0.243), but mortality risks were significantly higher in the low UACR and high UNAPCR subgroup (HR 2.204, 95% CI 1.448-3.356, P < 0.001) and in the high UACR with high UNAPCR subgroup (HR 1.796, 95% CI 1.451-2.221, P < 0.001). In the multivariable Cox regression model with inclusion of both UACR and UNAPCR, UNAPCR ≥ 120 mg/g was significantly associated with an increased mortality risk (HR 1.655, 95% CI 1.324-2.070, P < 0.001), but UACR ≥ 30 mg/g was not significantly associated with mortality risk (HR 1.046, 95% CI 0.820-1.334, P = 0.717). In conclusion, UNAPCR is an independent predictor of all-cause mortality in patients with type 2 DM.

URINARY EXCRETION OF ALPHA-ACTININ-4 AND TIGHT JUNCTION PROTEIN 1 IN PATIENTS WITH TYPE 2 DIABETES AND DIFFERENT PATTERNS OF CHRONIC KIDNEY DISEASE.

Abnormalities of the cytoskeleton and the slit diaphragm of podocytes have been attributed to diabetic nephropathy. In this study, we assessed urinary excretion of alpha-actinin-4 (ACTN-4), a cytoskeleton protein and a component of the slit diaphragm, and tight junction protein 1 (TJP-1, or ZO-1), a peripheral membrane protein that forms molecular complexes with actin filaments, in patients with type 2 diabetes (T2D) and albuminuric or non-albuminuric chronic kidney disease (CKD). The study included 140 patients with long-term T2D (≥10 years) and 20 healthy subjects as control. Patterns of CKD were identified based on the estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR). Urinary ACTN-4 and TJP-1 were assessed by ELISA. Patients with T2D had increased urinary excretion of ACTN-4 (p=0.03) and TJP-1 (p=0.006). In logistic regression models, both ACTN-4 and TJP-1 demonstrated associations with albuminuric CKD (UACR ≥3.0 mg/mmol and eGFR <60 mL/min×1.73 m2) after adjusting to age, sex, diabetes duration, HbA1c, and smoking. In ROC-analysis, TJP-1 excretion ≥70 pg/mmol was associated with albuminuric CKD (OR 5.45, 95% CI 1.96-15.18, p=0.001). The results demonstrate that elevated urinary ACTN-4 and TJP-1 are associated specifically with albuminuric CKD, but not with non-albuminuric CKD, in T2D patients.

Human In Vitro Oxidized Low-Density Lipoprotein (oxLDL) Increases Urinary Albumin Excretion in Rats.

Hypercholesterolemia-associated oxidative stress increases the formation of oxidized low-density lipoprotein (oxLDL), which can affect endothelial cell function and potentially contribute to renal dysfunction, as reflected by changes in urinary protein excretion. This study aimed to investigate the impact of exogenous oxLDL on urinary excretion of albumin and nephrin. LDL was isolated from a patient with familial hypercholesterolemia (FH) undergoing lipoprotein apheresis (LA) and was oxidized in vitro with Cu (II) ions. Biochemical markers of LDL oxidation, such as TBARS, conjugated dienes, and free ε-amino groups, were measured. Wistar rats were treated with a single intraperitoneal injection of PBS, LDL, or oxLDL (4 mg of protein/kg b.w.). Urine was collected one day before and two days after the injection. We measured blood lipid profiles, urinary protein excretion (specifically albumin and nephrin), and markers of systemic oxidative stress (8-OHdG and 8-iso-PGF2α). The results showed that injection of oxLDL increased urinary albumin excretion by approximately 28% (310 ± 27 µg/24 h vs. 396 ± 26 µg/24 h, p = 0.0003) but had no effect on nephrin excretion. Neither PBS nor LDL had any effect on urinary albumin or nephrin excretion. Additionally, oxLDL did not affect systemic oxidative stress. In conclusion, hypercholesterolemia may adversely affect renal function through oxidatively modified LDL, which interferes with the renal handling of albumin and leads to the development of albuminuria.

Association of the longitudinal trajectory of urinary albumin/creatinine ratio in diabetic patients with adverse cardiac event risk: a retrospective cohort study.

Objective: The baseline urinary albumin/creatinine ratio (uACR) has been proven to be significantly associated with the risk of major adverse cardiac events (MACE). However, data on the association between the longitudinal trajectory patterns of uACR, changes in glycated hemoglobin A1c (HbA1c), and the subsequent risk of MACE in patients with diabetes are sparse. Methods: This is a retrospective cohort study including 601 patients with type 2 diabetes mellitus (T2DM; uACR < 300 mg/g) admitted to The First Hospital of Shanxi Medical University and The Second Hospital of Shanxi Medical University from January 2015 to December 2018. The uACR index was calculated as urinary albumin (in milligrams)/creatinine (in grams), and latent mixed modeling was used to identify the longitudinal trajectory of uACR during the exposure period (2016-2020). The deadline for follow-up was December 31, 2021. The primary outcome was the MACE [a composite outcome of cardiogenic death, hospitalization related to heart failure (HHF), non-fatal acute myocardial infarction, non-fatal stroke, and acute renal injury/dialysis indications]. The Kaplan-Meier survival analysis curve was used to compare the risk of MACE among four groups, while univariate and multivariate Cox proportional hazards models were employed to calculate the hazard ratio (HR) and 95% confidence interval (CI) for MACE risk among different uACR or HbA1c trajectory groups. The predictive performance of the model, both before and after the inclusion of changes in the uACR and HbA1c, was evaluated using the area under the receiver operating characteristic (ROC) curve (AUC). Results: Four distinct uACR trajectories were identified, namely, the low-stable group (uACR = 5.2-38.3 mg/g, n = 112), the moderate-stable group (uACR = 40.4-78.6 mg/g, n = 229), the high-stable group (uACR = 86.1-153.7 mg/g, n = 178), and the elevated-increasing group (uACR = 54.8-289.4 mg/g, n = 82). In addition, five distinct HbA1c trajectories were also identified: the low-stable group (HbA1c = 5.5%-6.8%, n = 113), the moderate-stable group (HbA1c = 6.0%-7.9%, n = 169), the moderate-decreasing group (HbA1c = 7.4%-6.1%, n = 67), the high-stable group (HbA1c = 7.7%-8.9%, n = 158), and the elevated-increasing group (HbA1c = 8.4%-10.3%, n = 94). Compared with the low-stable uACR group, patients in the high-stable and elevated-increasing uACR groups were more likely to be older, current smokers, and have a longer DM course, higher levels of 2-h plasma glucose (PG), HbA1c, N-terminal pro-B-type natriuretic peptide (NT-proBNP), uACR, and left ventricular mass index (LVMI), while featuring a higher prevalence of hypertension and a lower proportion of ß-receptor blocker treatment (p < 0.05). During a median follow-up of 45 months (range, 24-57 months), 118 cases (19.6%) of MACE were identified, including 10 cases (1.7%) of cardiogenic death, 31 cases (5.2%) of HHF, 35 cases (5.8%) of non-fatal acute myocardial infarction (AMI), 18 cases (3.0%) of non-fatal stroke, and 24 cases (4.0%) of acute renal failure/dialysis. The Kaplan-Meier survival curve showed that, compared with that in the low-stable uACR group, the incidence of MACE in the high-stable (HR = 1.337, 95% CI = 1.083-1.652, p = 0.007) and elevated-increasing (HR = 1.648, 95% CI = 1.139-2.387, p = 0.009) uACR groups significantly increased. Similar results were observed for HHF, non-fatal AMI, and acute renal injury/dialysis indications (p < 0.05). The multivariate Cox proportional hazards models indicated that, after adjusting for potential confounders, the HRs for the risk of MACE were 1.145 (p = 0.132), 1.337 (p = 0.007), and 1.648 (p = 0.009) in the moderate-stable, high-stable, and elevated-increasing uACR groups, respectively. In addition, the HRs for the risk of MACE were 1.203 (p = 0.028), 0.872 (p = 0.024), 1.562 (p = 0.033), and 2.218 (p = 0.002) in the moderate-stable, moderate-decreasing, high-stable, and elevated-increasing groups, respectively. The ROC curve showed that, after adding uACR, HbA1c, or both, the AUCs were 0.773, 0.792, and 0.826, which all signified statistically significant improvements (p = 0.021, 0.035, and 0.019, respectively). Conclusion: A long-term elevated uACR is associated with a significantly increased risk of MACE in patients with diabetes. This study implies that regular monitoring of uACR could be helpful in identifying diabetic patients with a higher risk of MACE.

A candidate panel of eight urinary proteins shows potential of early diagnosis and risk assessment for diabetic kidney disease in type 1 diabetes.

Diabetic kidney disease (DKD) poses a significant health challenge for individuals with diabetes. At its initial stages, DKD often presents asymptomatically, and the standard for non-invasive diagnosis, the albumin-creatinine ratio (ACR), employs discrete categorizations (normal, microalbuminuria, macroalbuminuria) with limitations in sensitivity and specificity across diverse population cohorts. Single biomarker reliance further restricts the predictive value in clinical settings. Given the escalating prevalence of diabetes, our study uses proteomic technologies to identify novel urinary proteins as supplementary DKD biomarkers. A total of 158 T1D subjects provided urine samples, with 28 (15 DKD; 13 non-DKD) used in the discovery stage and 131 (45 DKD; 40 pDKD; 46 non-DKD) used in the confirmation. We identified eight proteins (A1BG, AMBP, AZGP1, BTD, RBP4, ORM2, GM2A, and PGCP), all of which demonstrated excellent area-under-the-curve (AUC) values (0.959 to 0.995) in distinguishing DKD from non-DKD. Furthermore, this multi-marker panel successfully segregated the most ambiguous group (microalbuminuria) into three distinct clusters, with 80% of subjects aligning either as DKD or non-DKD. The remaining 20% exhibited continued uncertainty. Overall, the use of these candidate urinary proteins allowed for the better classification of DKD and offered potential for significant improvements in the early identification of DKD in T1D populations.

Increasing obstructive sleep apnea risk is associated with albuminuria in Korean adults: cross-sectional analysis.

Several studies have shown an association between albuminuria and obstructive sleep apnea (OSA). However, studies on the relationship between the STOP-BANG questionnaire that can screen for OSA and microalbuminuria are still insufficient. Therefore, this study attempted to clarify the relationship between microalbuminuria and OSA risk using the STOP-BANG questionnaire in Korean adults. A total of 7478 participants (3289 men and 4189 women) aged over 40 were enrolled in the Korean National Health and Nutrition Examination Survey from 2019 to 2020. STOP-BANG questionnaire to screen OSA was obtained from subjects. The urinary albumin/creatinine ratio (ACR) and proteinuria were measured via a single dipstick to evaluate renal function. The high OSA risk group had a higher mean ACR value than the low OSA risk group (36.8 ± 172.2 vs 17.7 ± 82.5; P < 0.001). The proportion of subjects with values of 30 ≤ ACR < 300 mg/g (11.9% vs 6.1%; P < 0.001) and ACR > 300 mg/g (2.1% vs 0.7%; P < 0.001) was significantly higher in high OSA risk group. Multivariate logistic regression results confirmed that microalbuminuria (OR 1.279, 95% confidence interval (CI) 1.068-1.532, P = 0.008) was significantly correlated with high OSA risk. In addition, significant correlation with high OSA risk was also found in macroalbuminuria (OR 1.684, 95% CI 1.073-2.530, P = 0.022) and proteinuria (OR 1.355, 95% CI 1.030-1.783, P = 0.030). We confirmed a significant correlation between high OSA risk and albuminuria/proteinuria in Korean adults. Therefore, renal function evaluation is required in high OSA risk patients, and OSA diagnosis through PSG test and treatment is necessary.

Paper spray mass spectrometry combined with machine learning as a rapid diagnostic for chronic kidney disease.

A new analytical method for chronic kidney disease (CKD) detection utilizing paper spray mass spectrometry (PS-MS) combined with machine learning is presented. The analytical protocol is rapid and simple, based on metabolic profile alterations in urine. Anonymized raw urine samples were deposited (10 µL each) onto pointed PS-MS sample strips. Without waiting for the sample to dry, 75 µL of acetonitrile and high voltage were applied to the strips, using high resolution mass spectrometry measurement (15 s per sample) with polarity switching to detect a wide range of metabolites. Random forest machine learning was used to classify the resulting data. The diagnostic performance for the potential diagnosis of CKD was evaluated for accuracy, sensitivity, and specificity, achieving results >96% for the training data and >91% for validation and test data sets. Metabolites selected by the classification model as up- or down-regulated in healthy or CKD samples were tentatively identified and in agreement with previously reported literature. The potential utilization of this approach to discriminate albuminuria categories (normo, micro, and macroalbuminuria) was also demonstrated. This study indicates that PS-MS combined with machine learning has the potential to be used as a rapid and simple diagnostic tool for CKD.

Soluble tumor necrosis factor receptor type 1 is an alternative marker of urinary albumin-creatinine ratio and estimated glomerular filtration rate for predicting the decline of renal function in subjects with type 2 diabetes mellitus.

BACKGROUND: Urinary albumin-creatinine ratio (UACR) and estimated glomerular filtration rates (eGFR) help predict worsening diabetic kidney disease (DKD) but have their limitations. Soluble tumor necrosis factor receptor type 1 (sTNFR1) is a biomarker of DKD. The predictive abilities of sTNFR1 and UACR plus eGFR have not been compared. METHODS: This prospective cohort study included patients with type 2 diabetes (T2D) to identify the risk factors of worsening DKD. Renal events were defined as > 30 % loss in eGFR based on consecutive tests after 6 months. The associations of sTNFR1, UACR, and eGFR levels and the risks of renal events were tested using a Cox regression model and the area under the curve (AUC) was compared between sTNFR1 levels and UACR plus eGFR using receiver-operating characteristic (ROC) analysis. The accuracy of stratification was evaluated using Kaplan-Meier analysis. RESULTS: Levels of sTNFR1 and UACR were associated with risks of > 30 % decline in eGFR after adjusting for relevant factors. The association between sTNFR1 levels and renal outcomes was independent of UACR and eGFR at baseline. The AUC of sTNFR1 level was comparable with that of combined UACR and eGFR (0.73 vs. 0.71, respectively, p = 0.72) and the results persisted for quartile groups of sTNFR1 and risk categories of Kidney Disease: Improving Global Outcomes (KDIGO) (0.70 vs. 0.71, respectively, p = 0.84). Both stratifications by sTNFR1 levels and KDIGO were accurate. CONCLUSION: sTNFR1 could be an alternative marker for identifying patients with diabetes at risk of declining renal function.

Dapagliflozin Reduces Urinary Kidney Injury Biomarkers in Chronic Kidney Disease Irrespective of Albuminuria Level.

The beneficial effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors in patients with chronic kidney disease (CKD) with low albuminuria levels have not been established. This study aimed to compare the effects of dapagliflozin on kidney injury biomarkers in patients with CKD stratified by albuminuria level. We prospectively enrolled healthy volunteers (HVs; n = 20) and patients with CKD (n = 54) with and without diabetes mellitus. Patients with CKD were divided into two age-matched and sex-matched subgroups according to urinary albumin-creatinine ratio (uACR) levels (<300 mg/g and ≥300 mg/g). The CKD group received dapagliflozin (10 mg/day). Urine samples were collected before treatment and after 3 and 6 months of dapagliflozin. Urinary kidney injury molecule-1 (KIM-1), interleukin-1ß (IL-1ß), and mitochondrial DNA nicotinamide adenine dinucleotide dehydrogenase subunit-1 (mtND1) copy number were measured. The estimated glomerular filtration rate (eGFR) of patients with CKD was lower than that of HVs (P < 0.001). During the study period, eGFR decreased and uACR did not change in the CKD group. Kidney injury markers were significantly elevated in patients with CKD compared with those in HVs. Dapagliflozin reduced urinary KIM-1, IL-1ß, and mtDNA copy number in patients with CKD after 6 months of treatment. In further, the levels of urinary KIM-1 and IL-1ß, patients with CKD decreased after 6 months of dapagliflozin treatment regardless of albuminuria level. Dapagliflozin reduced urinary kidney injury biomarkers in patients with CKD, regardless of albuminuria level. These findings suggest that SGLT2 inhibitors may also attenuate the progression of low albuminuric CKD.

Study of Neutrophil Gelatinase Associated Lipocalin and Kidney Injury Molecule-1 in Patients with Type 2 Diabetes Mellitus Nephropathy.

BACKGROUND: There is a need for accurate and rapid biomarkers for the early diagnosis of diabetic nephropathy (DN). We aimed to study the accuracy of urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary kidney injury molecule-1 (uKIM-1), and blood NGAL (bNGAL) in type 2 diabetics as biomarkers for diagnosis of DN. METHODS: The study was a retrospective case-control study that included 30 control subjects, 40 diabetics with normo-albuminuria < 30 mg/g and eGFR > 60 mL/minute/1.73 m2, and 30 diabetics with albuminuria > 30mg/g and eGFR < 60mL/minute/1.73 m2. Blood and urine samples were obtained to determine levels of bNGAL, uNAGAL, and uKIM1. RESULTS: There was a significant increase in bNGAL, uNGAL, uKIM 1, uNGAL/creatinine and uKIM 1/creatinine among diabetics with albuminuria compared to diabetics with normoalbuminuria and normal control (p < 0.001 for all markers). For diagnosis of early DN, both bNGAL and uKIM 1 had sensitivity and specificity of 100% for each at cutoff values of 322.5 pg/mL and 74.25 ng/mL, respectively. uNGAL had a sensitivity of 97.5% and a spec-ificity of 100% at a cutoff point of 565 ng/mL. uKIM1/creatinine at a cutoff of 51.2 had a sensitivity of 100% and specificity of 100%. CONCLUSIONS: The present study highlights the accuracy of urinary KIM1 and NGAL and blood NGAL as biomarkers for the diagnosis of nephropathy in the early stage of diabetic nephropathy. There were positive correlations with kidney function tests creatinine, blood urea nitrogen, and the presence of albuminuria.

Urinary Prostaglandin E2 Excretion and the Risk of Cardiovascular and Kidney Disease.

BACKGROUND: Inhibition of prostaglandin synthesis by nonsteroidal anti-inflammatory drugs is associated with cardiovascular mortality and kidney disease. This study hypothesizes that urinary prostaglandin E2 (PGE2) and PGE2 metabolite (PGEM) excretions are markers of cardiovascular and kidney health, because they reflect both systemic and kidney-derived PGE2 production. METHODS AND RESULTS: PGE2 and PGEM were measured in spot urine samples from 2291 participants (≥55 years old) of the population-based Rotterdam Study. Urinary PGE2 and PGEM excretions were analyzed using linear regression analyses to identify cross-sectional associations with cardiovascular risk factors and baseline estimated glomerular filtration rate (eGFR). Longitudinal associations with cardiovascular mortality and kidney outcomes (eGFR <60 or <45 mL/min per 1.73 m2 and the composite outcome 40% eGFR loss or kidney failure) were assessed with Cox regression. Urinary PGE2 and PGEM excretions were higher with increasing age, lower eGFR, smoking, diabetes, and albuminuria. A 2-fold higher urinary PGE2 and PGEM excretion was associated with a higher risk of cardiovascular mortality (28 825 patient-years; 160 events; PGE2 hazard ratio [HR], 1.27, [95% CI, 1.06-1.54]; PGEM HR, 1.36 [95% CI, 1.10-1.67]). Higher PGE2 excretions were also associated with a higher risk of incident eGFR <60 mL/min per 1.73 m2 (31 530 person-years; 691 events; HR, 1.13 [95% CI, 1.02-1.25]) with similar HRs for the other kidney outcomes. CONCLUSIONS: Urinary PGE2 and PGEM excretions are novel markers for the presence and progression of cardiovascular and kidney disease. Future studies should address whether these associations are causal and can be targeted to improve cardiovascular and kidney outcomes.

A comprehensive analysis of albuminuria in canine chronic kidney disease.

BACKGROUND: Albuminuria, an important marker of decreased kidney function in chronic kidney disease (CKD), is not routinely used for CKD detection or proteinuria appearance. Its relationships with biochemical parameters and blood pressure in dogs are poorly understood. OBJECTIVES: This study aimed to evaluate the relationship of albuminuria with various CKD markers, its correlation with the urinary protein to creatinine ratio (UPC), and hypertension in dogs with early stages of CKD. It also sought to determine the usability of the urinary albumin to creatinine ratio (UAC) for CKD screening. METHODS: The study reviewed records of 102 dogs, categorising them into four groups based on disease status. UAC and UPC ratio, biochemistry and haematology variables, age, and systolic blood pressure were determined. RESULTS: The Pearson's correlation coefficient between log-transformed values of UPC and UAC was r = 0.902 (95% CI: 0.87 to 0.93). Median UAC ratio values were 2.1 mg/g for the Healthy control group (n = 17), 54.2 mg/g for early stages CKD (n = 42), 5.8 mg/g for Acute sick control (n = 30), and 104 mg/g for Chronic sick control (n = 13). Thresholding UAC ratio as an indicator for impaired kidney function with the threshold of 10 mg/g (established based on the receiver operating characteristic curve) had a sensitivity 81.8%, specificity of 89.4%, positive predictive value (PPV) 90%, and negative predictive value (NPV) 80.1%. The correlation of UAC with biochemistry and haematology variables was statistically significant; for SDMA (µg/L), it was r = 0.566 and for other variables, it was weak to moderate. UAC was markedly elevated in cases of severe hypertension. CONCLUSIONS: UAC ratio was significantly different among dogs with impaired and not impaired kidney function. The correlation strength for the UAC and UPC ratios was high. UAC ratio may be a promising marker for proteinuria analysis in dogs with CKD or other kidney function alterations.

The impact of urinary albumin-creatinine ratio and glomerular filtration rate on long-term mortality in patients with heart failure: The National Health and Nutrition Examination Survey 1999-2018.

BACKGROUND AND AIMS: The urinary albumin‒creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) are important markers of renal dysfunction, but few studies have simultaneously examined their impact on long-term mortality in patients with heart failure (HF). METHODS AND RESULTS: This study included patients with HF from the National Health and Nutrition Survey from 1999 to 2018. The fully adjusted Cox proportional risk model was adopted, and propensity score matching (PSM) was also used for risk adjustment. Among 988 patients, a median follow-up of 7.75 years was recorded. A higher UACR corresponded to a higher risk of cardiovascular death (P < 0.001 for trend). No statistically significant difference was found in the trend of eGFR risk stratification on the risk of cardiovascular death (P = 0.09 for trend). After PSM, the results showed that when grouped by UACR, the high-risk group had a higher risk of cardiovascular death regardless of a cutoff value of 30 or 300 mg/g (all P < 0.05). When grouped by eGFR, regardless of a cutoff value of 45 or 30 mL/min/1.73 m2, compared to the low-risk group, the high-risk group did not have a statistically significant increase in cardiovascular death (P = 0.086 and P = 0.093, respectively). The subgroup analysis of the main outcome showed an interaction between the UACR and eGFR (P = 0.044). CONCLUSIONS: Both the UACR and eGFR are markers for predicting the progression of HF, but the UACR may be a more important indicator than the eGFR, and they synergistically and complementarily reflect the long-term cardiovascular risk of HF patients.

Urine Albumin Measurements in Clinical Diagnostics.

BACKGROUND: Measurement of urine albumin is critical for diagnosis, risk classification, and monitoring of chronic kidney disease (CKD). Guidelines recommend clinical decision cutoffs for the urine albumin-to-creatinine ratio (ACR) of 30 and 300 mg/g (3 and 30 mg/mmol). However, differences among manufacturers' routine urine albumin measurement procedures have been found to exceed 40%, suggesting CKD diagnosis and risk classification may vary depending upon the specific measurement procedure implemented in the laboratory. CONTENT: This review discusses urine albumin pathophysiology and clinical practice guideline recommendations for CKD. The review also provides recommendations for urine specimen collection and storage, and results reporting for the ACR. Recent advances in measurement techniques and development of reference systems intended to facilitate standardization of urine albumin measurements are reviewed. SUMMARY: Urine albumin is an important measurement procedure used for diagnosis, risk classification, and management of CKD. Urine albumin results should be reported as the ACR using quantitative measurement procedures. Random urine collections used for albuminuria screening should be followed by confirmation with first morning void collections to reduce variation and increase diagnostic accuracy for urine albumin measurement. Most measurement procedures utilize immunoturbidimetric or immunonephelometric techniques. However, results vary significantly among measurement procedures, potentially resulting in differences in classification or risk assessment for CKD. The National Institute for Standards and Technology (NIST) and other laboratories are developing reference systems, including liquid chromatography-tandem mass spectrometry candidate reference measurement procedures and reference materials, to enable standardization of routine measurement procedures.

Development of a reference interval for urinary ammonia-to-creatinine ratio in feline patients.

BACKGROUND: Disruption of acid-base homeostasis can lead to many clinical problems. Ammonia excretion by the kidneys is critical to maintaining acid-base homeostasis through bicarbonate production. Measurement of ammonia excretion may help determine if the kidneys are properly functioning in maintaining acid-base balance. Reference intervals are essential tools for clinical decision-making but do not currently exist for urinary ammonia-to-creatinine ratio (UACR) in feline patients. OBJECTIVE: This study aimed to generate a reference interval (RI) for UACR in healthy adult cats. METHODS: The study used samples from client-owned adult healthy cats that presented to the University of Florida Primary Care and Dentistry service (n = 92). Physical examination, serum biochemistry, urinalysis, urine ammonia, and creatinine concentrations were measured. Cats were excluded if there were significant abnormalities in their urinalysis or biochemistry panel. The RI for UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. The UACR was evaluated for correlation with serum bicarbonate, weight, age, and sex. RESULTS: The RI for UACR was 3.4-20.7 with 90% confidence intervals for the lower and upper limits of (3.0-3.7) and (16.0-23.7), respectively. No significant correlation with age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR. CONCLUSIONS: Establishing an RI for UACR in healthy adult cats will allow further studies to determine if changes in UACR are observed during specific disease states.

Urine albumin-to-creatinine ratio diurnal variation rate predicts outcomes in idiopathic membranous nephropathy.

BACKGROUND: Idiopathic membranous nephropathy (IMN) is a leading cause of end-stage renal disease (ESRD). The purpose of this study was to evaluate whether urinary albumin-to-creatinine ratio (UACR) diurnal variation rate calculated by spot urinary protein test predicts 1-year nephrotic outcomes as a biomarker of proteinuria severity in patients with IMN. METHODS: Patients' baseline demographics, blood and urinary biomarkers, and clinical and pathological characteristics were collected retrospectively. Urine samples were collected at 7:00 (before breakfast) and 19:00 (after dinner) to calculate the UACR diurnal variation rate. A prediction model for no remission (NR) was developed statistically based on differences between prognosis groups. Receiver operating characteristic curve (ROC) analysis was performed to evaluate prediction abilities and determine optimal cut-off points of the model and UACR diurnal variation rate alone. RESULTS: The formula for calculating the probability of NR was exp(L)/(1 + exp(L)), where the linear predictor L = - 22.038 + 0.134 × Age (years) + 0.457 × 24-h urinary protein + 0.511 × blood urea nitrogen (BUN) + 0.014 × serum uric acid (SUA) + 2.411 if glomerular sclerosis + 0.816 × fasting blood glucose (FBG)-0.039 × UACR diurnal variation rate (%). Optimal cut-off points for NR prediction by the final model and UACR diurnal variation rate alone were 0.331 and 58.5%, respectively. Sensitivity and specificity were 0.889 and 0.859 for the final model, and 0.926 and 0.676 for UACR diurnal variation rate alone. CONCLUSION: UACR diurnal variation using spot urinary protein is a simpler way to predict nephrotic outcomes and is a highly sensitive screening tool for identifying patients who should undergo further comprehensive risk assessment.

Trajectory of Urine Albumin-Creatinine Ratio in Patients with Acute Heart Failure.

INTRODUCTION: Albuminuria is prevalent in patients with chronic heart failure and is a risk factor for disease progression. However, its clinical meaning in acute heart failure remains elusive. This study analyzed the trajectory of urine albumin to creatinine ratio (UACR) between admission and discharge and its association with decongestion. METHODS: In this prospective observational study, 63 patients were enrolled. UACR, B-type natriuretic peptide (BNP), and clinical congestion score (CCS) were obtained at admission and discharge. We used linear mixed regression analysis to compare changes in the natural logarithm of UACR (logUACR) and its association with changes in markers of decongestion. Estimates were reported as least squares mean with their respective 95% CIs. RESULTS: The median age of the study population was 87 years, 68.5% were women, and 69.8% had a left ventricular ejection fraction >50%. LogUACR at discharge significantly decreased in the overall population compared to admission (Δ -0.47, 95% CI: -0.78 to -0.15, p value = 0.003). The magnitude of UACR drop at discharge was associated with changes in surrogate markers of decongestion. Patients who showed a greater reduction in BNP at discharge exhibited a greater reduction in UACR (p = 0.016). The same trend was also found with clinical decongestion, as assessed by changes in CCS, however, without achieving statistical significance (p = 0.171). UACR change at discharge was not associated with changes in serum creatinine (p value = 0.923). CONCLUSION: In elderly patients with AHF and volume overload, the level of UACR significantly decreased upon discharge compared to admission. This reduction in UACR was closely linked to decreases in BNP.

Determination of pentoxifylline efficacy on microalbuminuria in patients with type-2 diabetes.

BACKGROUND: Diabetic nephropathy is a clinical syndrome characterized by persistent albuminuria and progressive impairment in renal function. Pentoxifylline is a non-specific inhibitor of phosphodiesterase with anti-inflammatory properties which may have therapeutic potency in patients with diabetic kidney disease. OBJECTIVE: The present study is aimed at evaluating the efficacy of pentoxifylline as a treatment strategy for alleviating the microalbuminuria in type-2 diabetic patients with nephropathy. METHODS: This double-blind randomized clinical trial was performed on outpatients with type 2 diabetic nephropathy who presented urine albumin excretion of 30-300 mg per 24 hours on at least three consecutive occasions. A total of 58 patients were randomly assigned to the treatment and control groups. The treatment group (n=29) received pentoxifylline (400 mg/day) for 3 months in addition to the standard drugs for diabetic nephropathy (Raas blockers), while the control group (n=29) received placebo as add-on therapy. Finally, urine albumin test was measured before and after 3 months of treatment and compared between the two groups. RESULTS: Before the intervention, no significant difference in the levels of albuminuria was observed between the two groups (153.21±130.80 mg/day vs. 159.93 ±130.45; p=0.845); but after 12 weeks of treatment, albuminuria in the treatment group was significantly reduced compared to the placebo group (29.59 ±27.88 mg/day vs. 160.48±129.53 mg/day; p<0.0001). At the end of the study, the response rate to treatment (more than 50% reduction in albuminuria) was 89.7% in the pentoxifylline group, while no response to treatment was observed in the placebo group (p<0.0001). CONCLUSIONS: Pentoxifylline as add-on therapy to the conventional treatment (Raas blockers) may reduce the microalbuminuria in patients with diabetic nephropathy without any side effects.