Protein and albumin-to-creatinine ratios in random urines accurately predict 24 h protein and albumin loss in patients with kidney disease

Urine Dipstick Analysis on Automated Platforms: Is a Reliable Screening Tool for Proteinuria? An Experience from Umberto I Hospital in Rome

Urinalysis is commonly used as a screening tool for kidney disease. In many cases, the dipstick urine assay includes the assessment of albumin/protein and creatinine; consequently, the value of their ratio is available on the urine section report. Identification of albuminuria/proteinuria at early stages is an important issue to prevent or at least delay the onset of chronic kidney disease (CKD), kidney failure, and the progression of cardiovascular damage linked to the kidney's loss of function. Sensitive and specific diagnostic methods are required for the assessment of such an important biomarker: urine albumin, creatinine, and their ratio (ACR) measured with quantitative assays are considered the gold standard. Routine dipstick methods (more rapid and at a lower cost) are intended for wide population screening. The aim of our study was to verify the reliability of an automated urinalysis dipstick method by comparing the results with the quantitative test of creatinine and albumin performed on a clinical chemistry platform. The first-morning voids of 249 patients who arrived from different departments were analyzed in the Central Laboratory of the University Hospital Policlinico Umberto I in Rome. We found a good correlation between the two assays, even though we observed that the dipstick assessment tends to overestimate the ACR's value, disclosing a higher number of false positives if compared to the reference method. As an important novelty in this study, we analyzed our data considering age (starting from pediatric to geriatric patients) and sex as variables for a sub-stratification of the participants. Our results show that positive values need to be confirmed with quantitative methods, especially in women and younger people, and that from samples that resulted as diluted at the dipstick assay, the ACR's values can be obtained if they are reanalyzed with quantitative assays. Moreover, patients with microalbuminuria (ACR 30-300 mg/g) or severe albumin urinary excretion (ACR > 300 mg/g) should be reanalyzed using quantitative methods to obtain a more reliable calculation of the ACR.

Albumin-to-protein ratio in spot urine samples for analysis of proteinuria selectivity in chronic kidney disease

INTRODUCTION

The albumin-to-creatinine ratio and total protein-to-creatinine ratio in spot urine samples have already been validated as surrogates for 24-hour albuminuria and proteinuria measurements. Thus, we hypothesized that the type of proteinuria, detected by the electrophoretic pattern of 24-hour urine, could be predicted by the simple proportion of albumin in the total urine protein content, using the albumin-to-protein ratio (APR). Our study sought to validate the use of APR as a cheaper substitute for urinary protein electrophoresis (UPE).

METHODS

Using different mathematical models, we compared, the albumin fraction in 24-hour urine samples by electrophoresis and the APR ratio in spot samples from 42 outpatients with chronic kidney disease (CKD).

RESULTS

A strong log-order correlation r = 0.84 (0.75-0.92; 95% CI, p = 0.001) was observed between APR and the albumin fraction in the UPE.

CONCLUSION

The APR can substitute electrophoresis in CKD outpatients.

RISK FACTORS FOR DIABETIC NEPHROPATHY IN DIABETES MELLITUS TYPE 1

OBJECTIVE

The aim: To find the risk factors of microalbuminuria and estimated Glomerular Filtration Rate (eGFR) in patients with type 1 diabetes mellitus.

PATIENTS AND METHODS

Materials and methods: One hundred ten patients of type 1 diabetes mellitus in this cross-sectional study at diabetic and endocrinology center in Al-Najaf during the period from September 2021 to March 2022. All patients were asked about sociodemographic characteristics (age, gender, smoking, duration of DM type1, family history of DM type1), measured (body mass index BMI, blood pressure) and laboratory investigations done to all patients (G.U.E, s. creatinine, lipid profile, HBA1C, calculated estimated Glomerular Filtration Rate (eGFR) and Spot Urine Albumin-Creatinine Ratio (ACR).

RESULTS

Results: Out of 110 patients, 62 male and 48 female, the mean age was (22±12). The patients with microalbuminuria (ACR ≥ 30 mg/g) show statistically significant with increase HBA1C, duration of DM type 1, total cholesterol (T.C), low density lipoprotein (LDL), triglycerides (TG) and family history of DM type 1, while there were not statistically significant with age, gender, smoking, BMI, eGFR, high density lipoprotein (HDL) and hypertension. Patients with eGFR<90mL/min/1.73m2 show statistically significant with increase HBA1C, duration of DM type1, LDL, TG, T.C, while significantly decrease in HDL and there were not statistically significant with age, gender, smoking, family history of DM type 1, BMI and hypertension.

CONCLUSION

Conclusions: The degree of glycemic control, duration of type1 (DM) and dyslipidemia were associated with increased microalbuminuria and reduced eGFR (nephropathy). Family history of DM type1 was risk factor for microalbuminuria.

Razão albumina/proteína em amostras isoladas de urina para análise da seletividade de proteinúria na doença renal crônica

Resumo Introdução: A utilização da razão albumina/creatinina e da razão proteína total/creatinina em amostras isoladas de urina já foram validadas como substitutos para a albuminúria e proteinúria em 24 horas. Assim, nossa hipótese é que o tipo de proteinúria, dado pelo padrão eletroforético da urina de 24 horas, poderia ser previsto pela simples proporção de albumina no conteúdo total de proteínas na urina, utilizando a razão albumina/proteína (RAP). O presente estudo procurou validar o uso da RAP como um substituto mais prático e de menor custo da eletroforese de proteínas urinárias (EPU). Métodos: Foram utilizados diferentes modelos matemáticos a fim de comparar a fração de albumina pela eletroforese em amostras de urina de 24 horas e a RAP em amostras isoladas em 42 pacientes ambulatoriais com doença renal crônica. Resultados: Foi observada uma forte correlação logarítmica r = 0,84 (0,75–0,92; 95% CI, p = 0,001) entre a RAP e a fração de albumina pela EPU. Conclusão: A RAP pode substituir a eletroforese urinária em pacientes renais crônicos ambulatoriais.

Reference Intervals of Spot Urine Creatinine-to-Osmolality Ratio as a Surrogate of Urinary Creatinine Excretion Rate

A spot urine creatinine-to-osmolality ratio (sUCr/Osm) is proposed as a surrogate of the urinary excretion rate of creatinine (Cr) and convenient for forecasting serum Cr (SCr) trends. The lower the sUCr/Osm, the lower the excreted Cr amount accompanied by per unit of osmoles, the higher the risk of Cr accumulation. For exploring the reference intervals of sUCr/Osm in general adults, a cross-sectional analysis was performed on a subset of data from the National Health and Nutrition Examination Survey (NHANES) 2011–2012. Of the eligible 3,316 adults aged 18.0 to 79.9 years, the age (mean ± SD) was 45.2 ± 17.2 years old, women was 45.02%, body weight (BW) was 76.1 ± 14.5 kg, and African Americans was 23.6%. Blood urea nitrogen (BUN) was 12.6 ± 4.7 mg/dL; SCr was 0.89 ± 0.34 mg/dL. As spot urine Cr and osmolality were 127.1 ± 84.0 mg/dl and 649 ± 266 mOsm/kg, respectively, sUCr/Osm was 0.19 ± 0.08. With adjustment of factors related to personal urinary excretion of Cr and osmoles by multivariable regression analysis, the estimated sUCr/Osm (esUCr/Osm) for an individual was 0.153 × (age in year)^−0.070 × (BW in kg)^0.283 × 1.244 [if African American] × (BUN in mg/dL)^−0.310 × (SCr in mg/dL)^0.681. The index of sUCr/Osm to personalized esUCr/Osm was 1.05 ± 0.39. When only low urinary excretion of Cr is likely to be of clinical concern, further analysis showed 157 individuals (4.7%, outside the 5th percentile) had their original sUCr/Osm < 0.08; 157 had the sUCr/Osm indexed for personalized esUCr/Osm < 0.50.

Correlation between Random Urinary Protein-to-creatinine Ratio and 24-h Urinary Protein Excretion in Preeclampsia

This study aimed to determine the correlation between random urinary protein-to-creatinine ratio in single-voided urine samples and 24-h urinary protein excretion in pregnant women with preeclampsia. A cross-sectional study was conducted at the Department of Gynecology and Obstetrics, Abbasi Shaheed Hospital, Karachi, Pakistan, from July 2019 to June 2020. Fifty women with singleton pregnancy after 20 weeks of gestation with hypertension and 2+ proteinuria or more, according to a dipstick test, were included. Those with chronic hypertension; preexisting renal disease; gestational diabetes; eclampsia; hemolysis, elevated liver enzymes, a low platelet count syndrome; and coexisting urinary tract infections were excluded. Two random urine samples taken at 9:00 a.m. and 2:00 p.m. and 24-h urine samples were collected to evaluate the random urinary protein-to-creatinine and the 24-h protein excretion, respectively. The correlation coefficient (r) between them was calculated using Pearson's correlation test. The patients' mean age was 28.58 ± 5.09 years and their mean gestational age was 32.74 ± 4.44 weeks. Twenty-eight (56%) women were primigravidas, and 22 (44%) were multiparous. The average serum creatinine was 0.80 ± 0.16 mg/dL. The mean random urinary protein-to-creatinine ratio was 0.93 ± 0.7 mg/mg, and the mean 24-h urine was 481.08 ± 20.10 mL. A strong positive correlation was found between the protein-to-creatinine ratio and 24-h urinary protein excretion (r = 0.655; P = 0.01). We concluded that the protein-to-creatinine ratio in spot urine samples could be used as an alternative to in 24-h collection of urine to determine protein excretion in preeclamptic pregnant women.

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.

Association of urinary C-megalin with albuminuria and renal function in diabetes: a cross-sectional study (Diabetes Distress and Care Registry at Tenri [DDCRT 21])

BACKGROUND

A urinary biomarker sensitive to glomerular functional or structural changes in diabetic kidney disease is required. This study examined whether urinary C-megalin reflects renal function or albuminuria in diabetes.

METHODS

This was a cross-sectional study involving 1576 patients with type 1 or 2 diabetes. The exposure variables were estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR), and the outcomes were urinary C-megalin excretion and concentration. Two-part models were used to examine the associations between eGFR and UACR with urinary C-megalin excretion or concentration.

RESULTS

The UACR was linearly associated with urinary C-megalin excretion (per 100 mg/gCr of UACR; 11.8 fM/gCr [95% CI 8.9-14.7]). There was no association between decreasing eGFR and increasing urinary C-megalin excretion. The UACR was also linearly associated with the urinary C-megalin concentration (per 100 mg/gCr of UACR, 7.7 fM/L [95% CI 5.8-9.6]). At eGFR values > 60 mL/min/1.73 m², the eGFR and urinary C-megalin concentration were inversely linearly related (per 10 mL/min/1.73 m² decline, 7.7 fM/L [95% CI 0.2-15.1]).

CONCLUSION

Urinary C-megalin excretion as well as concentration levels are potentially useful biomarkers to detect early changes in diabetic kidney disease.

Effect of Conventional Medical Therapy or Laparoscopic Sleeve Gastrectomy on Urinary Albumin in Japanese Subjects with Severe Obesity: An Observational Study

INTRODUCTION

In patients with severe obesity, albuminuria can be improved by both conventional medical therapy and bariatric surgery. The purpose of this study was to compare the impact of weight loss achieved through conventional medical therapy or laparoscopic sleeve gastrectomy (LSG) on albuminuria in Japanese subjects with severe obesity and identify the factors involved.

METHODS

We retrospectively evaluated the clinical characteristics including the urinary albumin/creatinine ratio (UACR) of 340 consecutive subjects with a body mass index ≥35 who received LSG (n = 242) or medical therapy (n = 98) between 2010 and 2018 and were followed for at least 12 months.

RESULTS

The baseline of the UACR was not different between the 2 groups. At the 12-month follow-up, total weight loss (TWL) and decreases in glycosylated hemoglobin (HbA1c) and loge UACR were greater in the LSG group than in the medical therapy group (body weight; -35.7 kg vs. -8.0 kg, p < 0.001, HbA1c; -1.4% vs. -0.7%, p < 0.001, loge UACR; -0.3 vs. 0.9, p < 0.001). The rate of complete remission of diabetes was significantly higher in the LSG group than in the medical therapy group. At 12 and 36 months (n = 111 in the medical therapy group, n = 56 in the LSG group at 36 months), loge UACR increased in the medical therapy group, while it remained unchanged or decreased in the LSG group. In subjects with microalbuminuria and macroalbuminuria, changes in the loge UACR correlated with percent total body weight loss (%TWL) in both groups at 12 months. Percent TWL contributed independently to the change in the loge UACR, irrespective of whether LSG was performed. In receiver-operating characteristic analysis, a weight loss of 7.8% predicted a decrease in the UACR (∆UACR <0 at 12 months).

CONCLUSION

Our analysis suggests that albuminuria may increase over time if only medical therapy is continued. To improve albuminuria, weight loss may be more important than whether LSG is performed.

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.

24-h Urine Collection: A Relevant Tool in CKD Nutrition Evaluation

Dietary management is a cornerstone of Chronic Kidney Disease (CKD) monitoring, and dietary surveys often difficult to perform. We studied in a CKD patient cohort with two years follow-up, whether validated 24-h urine ionogram would be a relevant tool for diet evaluation and compliance. We included 404 non-dialysis CKD patients, with three evaluations, including repeated measurements of fractional renal creatinine clearance and 24-h urine collection. Completeness of the 24-h urine collection, assessed by daily urine creatinine excretion extrapolated from fractional creatinine clearance, was 64.6%, 75.5%, and 78.2% at the first, second, and third visits, respectively. One hundred sixty-eight patients (41.6%) had three complete collections, with a measured glomerular filtration of 42.3 mL/min/1.73 m² at baseline and prevalence of anemia and secondary hyperparathyroidism of 13.9% and 26.2%, respectively, increasing during follow-up to 15% and 31.5% (p < 0.001 and p < 0.001). The urine analysis showed at baseline a urine volume of above 2 L/day, and estimated sodium and protein intake within targets in 51.6% and 40.3% of cases, which improved during follow-up only for protein (to 45.9%, p < 0.0001). Our data suggest that a 24-h urine ionogram is an interesting, reliable tool in CKD patients for dietary monitoring to achieve target recommendation noteworthy salt and protein intake.

Diagnostic utility of protein to creatinine ratio (P/C ratio) in spot urine sample within routine clinical practice

The spot (random) urine protein to creatinine ratio (P/C ratio) is an alternative, fast and simple method of detecting and estimating the quantitative assessment of proteinuria. The aim of the work was to review the literature concerning the usefulness of spot urine P/C ratio evaluation in the diagnosis of proteinuria in the course of kidney disease, hypertension, gestational hypertension, preeclampsia, immunological diseases, diabetes mellitus, and multiple myeloma, and in the diagnosis of proteinuria in children. We searched the PubMed and Google Scholar databases using the following keywords: proteinuria, spot urine protein to creatinine ratio, spot urine P/C ratio, protein creatinine index, PCR (protein to creatinine ratio), P/C ratio and methods, Jaffe versus enzymatic creatinine methods, urine protein methods, spot urine protein to creatinine ratio versus ACR (albumin to creatinine ratio), proteinuria versus albuminuria, limitations of the P/C ratio. More weight was given to the articles published in the last 10-20 years. A spot urine P/C ratio >20 mg/mmol (0.2 mg/mg) is the most commonly reported cutoff value for detecting proteinuria, while a P/C ratio value >350 mg/mmol (3.5 mg/mg) confirms nephrotic proteinuria. The International Society for the Study of Hypertension in Pregnancy recommends a P/C ratio of 30 mg/mmol (0.3 mg/mg) for the classification of proteinuria in pregnant women at risk of preeclampsia. A high degree of correlation was observed between P/C ratio values and the protein concentration in 24-h urine collections. The spot urine P/C ratio is a quick and reliable test that can eliminate the need for a daily 24-h urine collection. However, in doubtful situations, it is still recommended to assess proteinuria in a 24-h urine collection. The literature review indicates the usefulness of the spot P/C ratio in various disease states; therefore, this test should be available in every laboratory. However, the challenge for the primary care physician is to know the limitations of the methods used to determine the protein and creatinine concentrations that are used to calculate the P/C ratio. Moreover, the P/C ratio cutoff used should be determined in individual laboratories because it depends on the patient population and the laboratory methodologies.

Proteinuria-take a closer look!

Proteinuria is a hallmark of kidney disease. Therefore, measurement of urine protein content plays a central role in any diagnostic work-up for kidney disease. In many cases, proteinuria analysis is restricted to the measurement of total protein content knowing that very high levels of proteinuria (nephrotic proteinuria) are characteristic of glomerular disease. Still, proteinuria can also be a manifestation of impaired tubular protein reabsorption or even be physiological. This review will discuss the physiology of renal protein handling and give guidance on a more sophisticated analysis of proteinuria differentiating albumin, low-molecular weight proteins and immunoglobulins. These non-invasive tests are available in most routine clinical laboratories and may guide the clinician in the diagnostic process before ordering far more expensive (molecular genetic testing) and/or invasive (kidney biopsy) diagnostics.

A New Artificial Urine Protocol to Better Imitate Human Urine

Artificial urine has many advantages over human urine for research and educational purposes. By closely mimicking healthy individuals’ urine, it may also be important in discovering novel biomarkers. However, up until now, there has not been any specific protocol to prove the similarity in terms of the chemical composition at the molecular level. In this study, a new artificial urine protocol is established to mimics the urine of healthy individuals. The multi-purpose artificial urine (MP-AU) presented here is compared with two other protocols most cited in literature. Furthermore, these three protocols are also compared with samples from 28 healthy young individuals. To do so, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) is used, according to which MP-AU shows a significantly close similarity with human urine. In formulating MP-AU, the infrared spectra of nine compounds is provided, making possible the band assignment of some absorption bands to certain compounds. Given its properties, the MP-AU protocol introduced here is both economical and practical, making it useful when designing comparative-controlled experiments.

Management of Hypertension in Chronic Kidney Disease

Chronic kidney disease (CKD) is an increasingly prevalent condition globally and is strongly associated with incident cardiovascular disease (CVD). Hypertension is both a cause and effect of CKD and affects the vast majority of CKD patients. Control of hypertension is important in those with CKD as it leads to slowing of disease progression as well as reduced CVD risk. Existing guidelines do not offer a consensus on optimal blood pressure (BP) targets. Therefore, an understanding of the evidence used to create these guidelines is vital when considering how best to manage individual patients. Non-pharmacological interventions are useful in reducing BP in CKD but are rarely sufficient to control BP adequately. Patients with CKD and hypertension will often require a combination of antihypertensive medications to achieve target BP. Certain pharmacological therapies provide additional BP-independent renoprotective and/or cardioprotective action and this must be considered when instituting therapy. Managing hypertension in the context of haemodialysis and following kidney transplantation presents further challenges. Novel therapies may enhance treatment in the near future. Importantly, a personalised and evidence-based management plan remains key to achieving BP targets, reducing CVD risk and slowing progression of CKD.

Prevalence of isolated non-albumin proteinuria in the US population tested for both, urine total protein and urine albumin: An unexpected discovery

BACKGROUND

Isolated non-albumin proteinuria (NAP) is a condition when urine total protein concentrations are elevated without elevation of urine albumin. The prevalence of NAP in the US population tested for both, urine total protein and albumin was assessed in this study.

METHODS

The database of a US nationwide laboratory network was queried for test results when random urine albumin was ordered together with urine total protein and also when timed 24-hour urine albumin was ordered together with urine total protein. The total prevalence of NAP in the US population tested for both, urine total protein and albumin was calculated for patient groups having normal and low-normal urine albumin (random and timed) with elevated and severely increased urine total protein (random and timed). Also, the prevalence of NAP was calculated for patients with normal urine albumin to assess the probability of missing proteinuria if only urine albumin is measured.

RESULTS

The prevalence of NAP in the random samples group was 10.1% (15.2% for females and 4.7% for males). Among patients with normal random albumin, there were 20.0% (27.3% of females and 10.7% of males) patients with NAP. The prevalence of NAP in the timed samples group was 24.6% (29.8% for females and 18.5% for males). Among patients with normal timed urine albumin, there were 36.2% (40.0% of females and 30.8% of males) patients with NAP. There was a strong positive association with female gender and NAP in most patients groups.

CONCLUSIONS

Testing for only urine (micro)albumin can miss up to 40% of females and 30.8% of males with gross proteinuria.

Association between Urine Albumin-to-Creatinine Ratio within the Normal Range and Incident Hypertension in Men and Women

PURPOSE

There have been few studies on gender difference in the impact of a urine albumin-to-creatinine ratio (UACR) within the normal range on the risk of hypertension. We evaluated whether the association between the UACR below the microalbuminuria range and the incident risk of hypertension is different between men and women.

MATERIALS AND METHODS

A total of 1173 individuals (442 men and 731 women) aged 40 to 70 years without hypertension was examined at baseline (2005-2008) and followed (2008-2011). We defined the UACR as the amount of albumin (mg/dL) divided by creatinine (g/dL) in randomly voided urine. The subjects were classified according to UACR tertile.

RESULTS

During an average of 2.6 years of follow-up, 57 men (12.9%) and 66 women (9.0%) developed hypertension. In multivariable-adjusted models, the odds ratio for new-onset hypertension comparing the highest and lowest tertiles of UACR was 1.83 [95% confidence interval (CI) 0.85-3.94] in men and 2.69 (95% CI 1.27-5.73) in women. In stratified analyses by menopausal status, higher tertiles of UACR were associated with an increased risk of incident hypertension in postmenopausal women.

CONCLUSION

Higher normal UACR levels were associated with an increased risk of incident hypertension in women. The UACR could have a clinical role in predicting the development of hypertension.

Measures of Urinary Protein and Albumin in the Prediction of Progression of IgA Nephropathy

BACKGROUND AND OBJECTIVES

Proteinuria is an independent predictor for IgA nephropathy (IgAN) progression. Urine albumin-to-creatinine ratio (ACR), protein-to-creatinine ratio, and 24-hour urine protein excretion (UPE) are widely used for proteinuria evaluation in clinical practice. Here, we evaluated the association of these measurements with clinical and histologic findings of IgAN and explored which was the best predictor of IgAN prognosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with IgAN were followed up for ≥12 months, were diagnosed between 2003 and 2012, and had urine samples available (438 patients). Spot urine ACR, protein-to-creatinine ratio, and 24-hour UPE at the time of renal biopsy were measured on a Hitachi Automatic Biochemical Analyzer 7180 (Hitachi, Yokohama, Japan).

RESULTS

In our patients, ACR, protein-to-creatinine ratio, and 24-hour UPE were highly correlated (correlation coefficients: 0.71-0.87). They showed good relationships with acknowledged markers reflecting IgAN severity, including eGFR, hypertension, and the biopsy parameter (Oxford severity of tubular atrophy/interstitial fibrosis parameter). However, only ACR presented with positive association with the Oxford segmental glomerulosclerosis/adhesion parameter and extracapillary proliferation lesions. The follow-up time was 37.0 (22.0-58.0) months, with the last follow-up on April 18, 2014. In total, 124 patients reached the composite end point (30% eGFR decline, ESRD, or death). In univariate survival analysis, ACR consistently had better performance than protein-to-creatinine ratio and 24-hour UPE as represented by higher area under the curve using time-dependent survival analysis. When adjusted for well known risk factors for IgAN progression, ACR was most significantly associated with the composite end point (hazard ratio, 1.56 per 1-SD change of standard normalized square root-transformed ACR; 95% confidence interval, 1.29 to 1.89; P<0.001). Compared with protein-to-creatinine ratio and 24-hour UPE, addition of ACR to traditional risk factors resulted in more improvement in the predictive ability of IgAN progression (c statistic: ACR=0.70; protein-to-creatinine ratio =0.68; 24-hour UPE =0.69; Akaike information criterion: ACR=1217.85; protein-to-creatinine ratio =1229.28; 24-hour UPE =1234.96; P<0.001).

CONCLUSIONS

In IgAN, ACR, protein-to-creatinine ratio, and 24-hour UPE had comparable association with severe clinical and histologic findings. Compared with protein-to-creatinine ratio and 24-hour UPE, ACR showed slightly better performance in predicting IgAN progression.

The urine albumin-to-creatinine ratio is a reliable indicator for evaluating complications of chronic kidney disease and progression in IgA nephropathy in China

OBJECTIVE

This study investigated the correlation between the albumin-to-creatinine ratio in the urine and 24-hour urine proteinuria and whether the ratio can predict chronic kidney disease progression even more reliably than 24-hour proteinuria can, particularly in primary IgA nephropathy.

METHODS

A total of 182 patients with primary IgA nephropathy were evaluated. Their mean urine albumin-to-creatinine ratio and 24-hour proteinuria were determined during hospitalization. Blood samples were also analyzed. Follow-up data were recorded for 44 patients. A cross-sectional study was then conducted to test the correlation between these parameters and their associations with chronic kidney disease complications. Subsequently, a canonical correlation analysis was employed to assess the correlation between baseline proteinuria and parameters of the Oxford classification. Finally, a prospective observational study was performed to evaluate the association between proteinuria and clinical outcomes. Our study is registered in the Chinese Clinical Trial Registry, and the registration number is ChiCTR-OCH-14005137.

RESULTS

A strong correlation (r=0.81, p<0.001) was found between the ratio and 24-hour proteinuria except in chronic kidney disease stage 5. First-morning urine albumin-to-creatinine ratios of ≥125.15, 154.44 and 760.31 mg/g reliably predicted equivalent 24-hour proteinuria 'thresholds' of ≥0.15, 0.3 and 1.0 g/24 h, respectively. In continuous analyses, the albumin-to-creatinine ratio was significantly associated with anemia, acidosis, hypoalbuminemia, hyperphosphatemia, hyperkalemia, hypercholesterolemia and higher serum cystatin C. However, higher 24-hour proteinuria was only associated with hypoalbuminemia and hypercholesterolemia. Higher tubular atrophy and interstitial fibrosis scores were also associated with a greater albumin-to-creatinine ratio, as observed in the canonical correlation analysis. Finally, the albumin-to-creatinine ratio and 24-hour proteinuria were associated with renal outcomes in univariate analyses.

CONCLUSION

This study supports the recommendation of using the albumin-to-creatinine ratio, rather than 24-hour proteinuria, to monitor proteinuria and prognosis in primary IgA nephropathy.

Urinary albumin excretion in healthy adults: a cross sectional study of 24-hour versus timed overnight samples and impact of GFR and other personal characteristics

Background

Urinary albumin can be measured in 24 h or spot samples. The 24 h urinary albumin excretion rate is considered the gold standard, but is cumbersome to collect. Instead, often an overnight sample is collected, and adjusted for dilution. Proxies for 24 h excretion rate have been studied in diabetics, but seldom in healthy individuals. Our aims were to compare 24 h and overnight albumin excretion, to assess the impact of personal characteristics, and to examine correlations between the 24 h excretion rate and proxies such as the albumin to creatinine ratio (ACR).

Methods

Separate 24 h and overnight urine samples were collected from 152 healthy kidney donors. Urinary creatinine, specific gravity, collection time, and sample volume determined. Differences between 24 h and overnight samples were examined, and the effects of age, sex, smoking, body mass, glomerular filtration rate, and urinary flow rate were assessed.

Results

The 24 h albumin excretion rate and ACR were both significantly higher than their overnight counterparts. Unadjusted albumin was unsurprisingly higher in the more concentrated overnight samples, while concentrations adjusted for specific gravity were similar. In multivariate analysis, the 24 h excretion rate and proxies were positively associated with glomerular filtration rate, as was ACR in overnight samples. There were positive associations between urinary albumin and body mass.

Conclusions

Proxies for the 24 h albumin excretion rate showed relatively high correlations with this gold standard, but differences due to sampling period, adjustment method, and personal characteristics were large enough to be worth considering in studies of albumin excretion in healthy individuals.

Spot protein/creatinine ratio in preeclampsia as an alternative for 24-hour urine protein

BACKGROUND

Proteinuria is a major component of preeclampsia. Urine protein measurement after 24-hour urine collection is the traditional standard method for the detection of proteinuria. It is time-consuming. As an alternative, random spot sampling for a urine protein to creatinine (P/C) ratio has been investigated.

AIMS

The aim of the study was to determine the diagnostic accuracy of the protein to creatinine ratio (P/C) compared with 24-hour urine collection for the detection of remarkable proteinuria and to evaluate the P/C ratio for different proteinuria ranges in patients with preeclampsia.

STUDY DESIGN

Case-control study.

METHODS

Two hundred and eleven pregnant women who met the criteria of preeclampsia comprised the study group and fifty three pregnant women were taken as the control group. Spot urine specimens for measuring P/C ratio were obtained taken immediately before 24-hour urine collection. The correlation between the P/C ratio in the spot urine samples and urinary protein excretion in the 24-hour collections was examined using the Spearman correlation test.

RESULTS

It was found a good positive correlation between the P/C ratio and 24-hour protein excretion, with a correlation coefficient (r) of 0.758. The best cut-off which gave the maximum area under the curve was 0.45 for 300 mg, 0.9 for 1000 mg, 1.16 for 2000 mg, 1.49 for 3000 mg, 2.28 for 4000 mg and 2.63 for 5000 mg per 24h. A P/C ratio above 0.9 strongly predicts significant proteinuria for more than 1 gram (AUC 0.97, 95% CI: 0.94-0.99 and sensitivity, specificity, positive and negative predictive value of 91%, 95.4%, 95.2%, and 91.2%, respectively).

CONCLUSION

The P/C ratio can be used as a screening test as a good predictor for remarkable proteinuria. The P/C ratio seems to be highly predictive for diagnosis to detect proteinuria over one gram and it could be used as a rapid alternative test in preeclamptic patients not to delay implementation treatment.

Preanalytical requirements of urinalysis

Urine may be a waste product, but it contains an enormous amount of information. Well-standardized procedures for collection, transport, sample preparation and analysis should become the basis of an effective diagnostic strategy for urinalysis. As reproducibility of urinalysis has been greatly improved due to recent technological progress, preanalytical requirements of urinalysis have gained importance and have become stricter. Since the patients themselves often sample urine specimens, urinalysis is very susceptible to preanalytical issues. Various sampling methods and inappropriate specimen transport can cause important preanalytical errors. The use of preservatives may be helpful for particular analytes. Unfortunately, a universal preservative that allows a complete urinalysis does not (yet) exist. The preanalytical aspects are also of major importance for newer applications (e.g. metabolomics). The present review deals with the current preanalytical problems and requirements for the most common urinary analytes.

Comparison of associations of urine protein-creatinine ratio versus albumin-creatinine ratio with complications of CKD: a cross-sectional analysis

BACKGROUND

Urine albumin-creatinine ratio (ACR) and protein-creatinine ratio (PCR) are important markers of kidney damage and are used for prognosis in persons with chronic kidney disease (CKD). Despite how commonly these measurements are done in clinical practice, relatively few studies have directly compared the performance of these 2 measures with regard to associations with clinical outcomes, which may inform clinicians about which measure of urinary protein excretion is best. We studied the association of ACR and PCR with common complications of CKD.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

3,481 participants with CKD in the Chronic Renal Insufficiency Cohort (CRIC) Study.

PREDICTORS

ACR and PCR.

OUTCOMES

We examined the association between ACR and PCR with measures of common CKD complications: serum hemoglobin, bicarbonate, parathyroid hormone, phosphorus, potassium, and albumin.

MEASUREMENTS

Restricted cubic spline analyses adjusted for estimated glomerular filtration rate (eGFR; calculated by the MDRD [Modification of Diet in Renal Disease] Study equation) were performed to study the continuous association with our predictors with each outcome.

RESULTS

Mean eGFR was 43±13 (SD)mL/min/1.73 m2 and median values for PCR and ACR were 140 and 46 mg/g, respectively. In continuous analyses adjusted for eGFR, higher ACRs and PCRs were similar and both were associated with lower serum hemoglobin, bicarbonate, and albumin levels and higher parathyroid hormone, phosphorus, and potassium levels. Across all outcomes, the associations of ACR and PCR were similar, with only small absolute differences in the outcome measure. Similar associations were seen in patients with diabetes mellitus.

LIMITATIONS

Participants largely had moderate CKD with low values for ACR and PCR, so results may not be generalizable to all CKD populations.

CONCLUSIONS

In persons with CKD, ACR and PCR are relatively similar in their associations with common complications of CKD. Thus, routine measurement of PCR may provide similar information as ACR in managing immediate complications of CKD.

Measurement of renal function in patients with chronic kidney disease

Chronic kidney disease affects millions of people worldwide and is associated with an increased morbidity and mortality as a result of kidney failure and cardiovascular disease. Accurate assessment of kidney function is important in the clinical setting as a screening tool and for monitoring disease progression and guiding prognosis. In clinical research, the development of new methods to measure kidney function accurately is important in the search for new therapeutic targets and the discovery of novel biomarkers to aid early identification of kidney injury. This review considers different methods for measuring kidney function and their contribution to the improvement of detection, monitoring and treatment of chronic kidney disease.

Random spot urine protein/creatinine ratio: a reliable method for monitoring lupus nephritis?

Background

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus (SLE) that can lead to end-stage renal disease. According to the Kidney Disease Outcomes Global Improving clinical Guidelines for Glomerulonephritis, spot urine protein/creatinine (P/C) ratio should be used for monitoring LN. However, some reports write that the random spot urine P/C ratio is unreliable in monitoring proteinuria in SLE glomerulonephritis patients. The aim of this study was to evaluate the agreement of these two assay methods.

Methods

The prospective observational study was performed. Fifty-three paired (total 106) spot and 24-h urine collections were evaluated. Statistical analysis: SPSS 20.0.

Results

Paired samples t-test did not reveal significant differences between the two-paired assay methods (spot P/C ratio versus 24-h proteinuria and 24-h P/C ratio) and a statistically significant correlation was observed between them: Pearson's coefficient of 0.847 (P < 0.001) and 0.863 (P < 0.001), respectively. However, after stratifying by degrees of proteinuria, a poor correlation was found in the range of <500 mg/day and only 26.6% of 24-h P/C ratio was explained by the spot P/C ratio. Adding to this, for proteinuria range between 500 and 1000 mg/day, there was no correlation (Pearson's −0.098; P > 0.05). In fact, only 1% of 24-h measurements could be explained by the spot P/C ratio.

Conclusions

Our study demonstrated a good correlation between 24-h proteinuria and random P/C ratio among patients with LN. However, this correlation was poor for proteinuria under 500 mg/day and did not exist in a range between 500 and 1000 mg/day. This finding is of greater importance because this range is quite common in patients with LN remission. Until further clarification, to the best of our knowledge, we maintain reluctant to completely substitute the 24-h collection by the P/C ratio especially when a renal flare is suspected, or before any change in therapy.

Chronic kidney disease in adolescent and adult patients with phenylketonuria

OBJECTIVES

A lifelong phenylalanine-restricted diet with supplementation of a phenylalanine-free amino acid formula is recommended in patients with phenylketonuria (PKU). The effect of a long-term PKU diet on renal function and blood pressure has not been investigated yet.

DESIGN

We analyzed renal function in 67 patients with PKU, aged 15-43 years, by measuring glomerular filtration rate (GFR) and effective renal plasma flow by isotope clearance ((51)Cr-EDTA, (123)J-Hippuran), estimated GFR, blood retention parameters, urinary protein and electrolyte excretion. Renal ultrasound and 24 h ambulatory blood pressure monitoring were performed additionally. Patients were divided into three groups according to their: 1) current diet (CD), i.e., daily protein intake: ICD <0.8 g/kg, IICD 0.8-1.04 g/kg, IIICD >1.04 g/kg; 2) life-long diet time (LDT), i.e., cumulative years of life in which daily protein intake exceeded dietary recommendations: ILDT <15 years, IILDT 15-19 years, IIILDT >19 years.

RESULTS

GFR was decreased in 19 % of the patients. With increasing protein intake, GFR decreased significantly (ICD 111 ml/min; IICD 105 ml/min; IIICD 99 ml/min. ILDT 112 ml/min; IILDT 103 ml/min; IIILDT 99 ml/min). Proteinuria was detected in 31 %, microalbuminuria in 7 %, and hypercalciuria in 23 % of the patients. 23 % of the patients had arterial hypertension, and 41 % revealed a nocturnal non-dipping status.

CONCLUSIONS

In patients with PKU on a lifelong diet we could detect impaired renal function in 19 %, proteinuria in 31 %, and arterial hypertension in 23 %. Thus, chronic kidney disease may develop in PKU patients, and routine renal function tests should be performed during long-term follow-up.

Characteristics of urinary and serum soluble Klotho protein in patients with different degrees of chronic kidney disease

Background

Klotho is a single-pass transmembrane protein, which appears to be implicated in aging. The purpose of the present study was to characterize the relationship between the soluble Klotho level and renal function in patients with various degrees of chronic kidney disease (CKD).

Methods

The levels of soluble Klotho in the serum and urine obtained from one hundred thirty-one CKD patients were determined by a sandwich enzyme-linked immunosorbent assay system.

Results

The amount of urinary excreted Klotho during the 24 hr period ranged from 1.6 to 5178 ng/day (median 427 ng/day; interquartile range [IR] 56.8-1293.1), and the serum Klotho concentration ranged from 163.9 to 2123.7 pg/ml (median 759.7 pg/ml; IR 579.5-1069.1). The estimated glomerular filtration rate (eGFR) was significantly correlated with the log-transformed values of the amount of 24 hr urinary excreted Klotho (r = 0.407, p < 0.01) and the serum Klotho levels (r = 0.232, p < 0.01). However, a stepwise multiple regression analysis identified eGFR to be a variable independently associated only with the log-transformed value of the amount of 24-hr urinary excreted Klotho but not with the log-transformed serum Klotho concentration. Despite the strong correlation between random urine protein-to-creatinine ratio and the 24 hr urinary protein excretion (r = 0.834, p < 0.01), a moderate linear association was observed between the log-transformed value of the amount of 24 hr urinary excreted Klotho and that of the urinary Klotho-to-creatinine ratio (Klotho/Cr) in random urine specimens (r = 0.726, p < 0.01).

Conclusions

The amount of urinary Klotho, rather than the serum Klotho levels, should be linked to the magnitude of the functioning nephrons in CKD patients. The use of random urine Klotho/Cr as a surrogate for the amount of 24-hr urinary excreted Klotho needs to be evaluated more carefully.

What is the best method of proteinuria measurement in clinical trials of endothelin receptor antagonists?

AIMS

To determine whether protein-creatinine ratio (PCR) and albumin-creatinine ratio (ACR) are comparable to 24h urine protein in terms of agreement and repeatability, and therefore whether they are suitable for monitoring and comparing reduction in proteinuria in clinical trials of endothelin receptor antagonists.

MAIN METHODS

Using data from a recent study of sitaxentan in 27 patients with proteinuric chronic kidney disease, the assays were compared with reference to their agreement, repeatability, the number of measurements required to obtain accurate results and correlation with reduction in proteinuria at baseline.

KEY FINDINGS

The median coefficient of variation was lower for PCR than 24h urine protein (25 vs. 28%) but the range was higher (70 vs. 47%). When converted into the same units, mean difference between 24h urine protein and both PCR (0.03 g/day), and ACR (0.10 g/day), was small. However, scatter increased with mean level of proteinuria, such that agreement fell substantially above 1.5 g/day. According to 2-factor within-subjects ANOVA, the assay used was not a significant source of variation (PCR p=0.63, ACR p=0.38). With 3 measurements at each time point, baseline proteinuria correlated equally well with change in proteinuria, and percentage change was detected accurately by all 3 methods.

SIGNIFICANCE

PCR and ACR may well be suitable replacements for 24h urine protein in the clinical trial context due to their similar accuracy and repeatability, greater convenience and lower cost. However, a randomised control trial comparing all 3 assays in a larger and more diverse population is necessary before 24h urine protein can be replaced.

Independent association of TG/HDL-C with urinary albumin excretion in normotensive subjects in a rural Korean population

BACKGROUND

The ratio of triglycerides (TG, mg/dl) to high-density lipoprotein cholesterol (HDL-C, mg/dl) is a reliable indicator of insulin resistance and atherosclerotic diseases in some ethnic groups. This study is performed to examine the association between TG/HDL-C and albuminuria.

METHODS

This cross-sectional study included 9094 adult subjects (4091 men, 5003 women) who were enrolled in the Korean Genomic Rural Cohort (KGRC) and aged 40 years or more. Albuminuria was defined as a urine albumin/creatinine ratio ≥ 30 mg/g. Participants were categorized into TG/HDL-C quartile.

RESULTS

Compared to the lowest TG/HDL-C quartile (<1.94 in men, <1.71 in women), the odds ratios (ORs) for albuminuria in participants who were categorized in the highest TG/HDL-C quartile (≥ 4.98 in men, ≥ 4.20 in women) were 1.30 (95% CI: 0.97-1.75) and 1.36 (1.03-1.79) in men and women, respectively, when adjusted for blood pressure and other covariates. In normotensive men and women, the ORs for albuminuria in the highest TG/HDL-C quartile were 1.58 (1.04-2.39) and 1.68 (1.15-2.45), respectively, even after fully adjusted. In contrast, TG/HDL-C was not associated with albuminuria in hypertensive subjects.

CONCLUSIONS

TG/HDL-C was independently associated with increased prevalence of albuminuria in normotensive rural Korean subjects aged 40 years or more in KGRC.

Assessment of proteinuria

Proteinuria is a strong predictor of adverse cardiovascular and kidney events, and an accurate assessment of proteinuria is important for the evaluation and management of CKD. Total urinary protein can be assessed using dipstick, precipitation, and electrophoresis methods. Urinary albumin, the predominant urinary protein in most proteinuric kidney diseases, can be assessed using an albumin-specific dipstick, immunochemical techniques, and size-exclusion high-performance liquid chromatography. Urine albumin may be immune-reactive, immune-unreactive, fragmented, and biochemically modified, and laboratory techniques have variable abilities to detect different types of albumin. Urine specimen for proteinuria assessment can either be obtained from a timed-collection or a spot urine sample. Spot urine protein- or albumin-to-creatinine ratios are preferred to a 24-hour urine sample in routine practice. Assessment of albuminuria rather than proteinuria is more clinically meaningful in patients with diabetic kidney disease, and proteinuria and albuminuria assessments both have a role in nondiabetic kidney disease and in general population screening. As measurement and sampling procedures for proteinuria assessment have yet not been standardized, it is important for physicians to be aware of different types of urinary proteins, albumins, laboratory techniques, and urine sampling methods.

Defective response of CD4(+) T cells to retinoic acid and TGFβ in systemic lupus erythematosus

Introduction

CD25⁺ FOXP3⁺ CD4⁺ regulatory T cells (Tregs) are induced by transforming growth factor β (TGFβ) and further expanded by retinoic acid (RA). We have previously shown that this process was defective in T cells from lupus-prone mice expressing the novel isoform of the Pbx1 gene, Pbx1-d. This study tested the hypothesis that CD4⁺ T cells from systemic lupus erythematosus (SLE) patients exhibited similar defects in Treg induction in response to TGFβ and RA, and that PBX1-d expression is associated with this defect.

Methods

Peripheral blood mononuclear cells (PBMCs) were collected from 142 SLE patients and 83 healthy controls (HCs). The frequency of total, memory and naïve CD4⁺ T cells was measured by flow cytometry on fresh cells. PBX1 isoform expression in purified CD4⁺ T cells was determined by reverse transcription polymerase chain reaction (RT-PCR). PBMCs were stimulated for three days with anti-CD3 and anti-CD28 in the presence or absence of TGFβ and RA. The expression of CD25 and FOXP3 on CD4⁺ T cells was then determined by flow cytometry. In vitro suppression assays were performed with sorted CD25⁺ and CD25^- FOXP3⁺ T cells. CD4⁺ T cell subsets or their expansion were compared between patients and HCs with two-tailed Mann-Whitney tests and correlations between the frequencies of two subsets were tested with Spearman tests.

Results

The percentage of CD25^- FOXP3⁺ CD4⁺ (CD25^- Tregs) T cells was greater in SLE patients than in HCs, but these cells, contrary to their matched CD25⁺ counterparts, did not show a suppressive activity. RA-expansion of TGFβ-induced CD25⁺ Tregs was significantly lower in SLE patients than in HCs, although SLE Tregs expanded significantly more than HCs in response to either RA or TGFβ alone. Defective responses were also observed for the SLE CD25^- Tregs and CD25⁺ FOXP3^- activated CD4⁺ T cells as compared to controls. PBX1-d expression did not affect Treg induction, but it significantly reduced the expansion of CD25^- Tregs and prevented the reduction of the activated CD25⁺ FOXP3^- CD4⁺ T cell subset by the combination of TGFβ and RA.

Conclusions

We demonstrated that the induction of Tregs by TGFβ and RA was defective in SLE patients and that PBX1-d expression in CD4⁺ T cells is associated with an impaired regulation of FOXP3 and CD25 by TGFβ and RA on these cells. These results suggest an impaired integration of the TGFβ and RA signals in SLE T cells and implicate the PBX1 gene in this process.

Comparison of estimated protein output and urine protein: creatinine ratio in first and second voids with 24-hour urine protein

BACKGROUND

Current UK guidelines for the identification, management and referral of chronic kidney disease advise an early-morning urine sample for the albumin:creatinine ratio or the protein:creatinine ratio (PCR) in order to quantify proteinuria. Estimated protein output (EPO) is an alternative and possibly better method of quantifying proteinuria which takes lean weight into consideration.

METHODS

We carried out a single-centre study of 36 adult patients with proteinuric nephropathy over a period of 18 months. Urinary PCR and EPO estimates of 24-hour urine protein were compared with 24-hour urine collections by Bland-Altman analysis.

RESULTS

Average 24-hour urine protein was 1.6 g (range 0.2-5.1 g). Best agreement with 24-hour protein was for first-void EPO (limits of agreement 0.33-1.59) followed by a second-void EPO (0.40-1.76), then second-void PCR (0.40-2.08) and lastly first-void PCR (0.28-2.03). None of the differences between estimates of urine protein excretion and 24-hour urine protein were statistically significant. All estimates of protein output had wide confidence intervals confirming that spot urine samples, while simple and convenient to do, are imprecise measures of 24-hour urine protein excretion.

CONCLUSION

When estimating 24-hour urine protein from a spot urine sample, EPO may be marginally more accurate than PCR, and first-void urine samples slightly better than second-void urine samples, but a first- or second-void PCR will suffice in most instances.

C1q deposition in the renal allograft: a report of 24 cases

C1q nephropathy is an uncommon glomerular disease characterized by dominant or codominant mesangial staining for C1q in the absence of systemic lupus erythematosus. There are no series in the literature addressing the significance of C1q deposition in the renal allograft. We retrospectively analyzed 24 patients, most of whom were white (83%) and male (63%), with a mean age at transplant of 31 years. None of the patients were diagnosed with C1q nephropathy in the native kidney or had any features of systemic lupus erythematosus. The mean time from transplant to detection of mesangial C1q deposits was 37 months (>12 months in 71% of cases). Half of the patients had a preceding infection. The indication for biopsy was surveillance (63%) or graft dysfunction (37%). At biopsy, 52% had proteinuria (>1g/day in only 17%). The mean creatinine was 1.8 mg per 100 ml. Only 9% developed hematuria and none had hypoalbuminemia. The glomerular pattern on light microscopy was mesangial hypercellularity (46%), focal segmental glomerulosclerosis (21%), or no lesions (33%). All cases showed intense (>or=2+) dominant (67%) or codominant (33%) mesangial staining for C1q on immunofluorescence. Mesangial electron-dense deposits were seen in 82% of cases. On follow-up (mean 1 year) of the 10 patients without rejection, most had stable creatinine with no or stable proteinuria, and none lost their graft. We conclude that C1q-dominant mesangial deposition in the renal allograft is a morphological pattern with no apparent clinical significance in the majority of patients. It is usually detected after the first year. The rate of preceding infection and the prevalence of proteinuria seem to be similar to the renal transplant recipients in general. Most cases show mesangial hypercellularity or no glomerular changes on light microscopy.

Comparison of different measures of urinary protein excretion for prediction of renal events

There are many methods to screen for abnormal amounts of proteinuria to identify patients at risk for progression of renal disease, but which method best predicts renal risk is unknown. Here, we analyzed a subset of 701 patients with type 2 diabetes and nephropathy participating in the Reduction of Endpoints in Non Insulin Dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan (RENAAL) trial to compare the ability of urinary protein excretion (UPE) and urinary albumin excretion (UAE) from a 24-hour urine collection and urinary albumin concentration (UAC) and the albumin:creatinine ratio (ACR) from a first-morning void in predicting renal events. The primary outcome measure was the time to a doubling of serum creatinine or end-stage renal disease. During follow-up, 202 events occurred. The hazard ratios for the risk of a renal outcome (95% CIs) associated with 1-SD increment in the log-transformed measures were 3.16 (2.60 to 3.86) for UAE, 3.02 (2.53 to 3.62) for UPE, 3.23 (2.67 to 3.91) for UAC, and 4.36 (3.50 to 5.45) for ACR. The area under the ROC curve was significantly higher for ACR compared with the other measures. In conclusion, measurement of the albumin:creatinine ratio in a first-morning void is the superior method to predict renal events in patients with type 2 diabetes and nephropathy.