Diagnostic accuracy of urine dipstick for proteinuria in older outpatients

Changes in urine dipstick proteinuria and its relation to the risk of diabetic retinopathy and neuropathy

BACKGROUND

Proteinuria is considered as a predictor for cardiovascular complications in diabetes mellitus (DM). However, no study has examined the association between changes in proteinuria and the risk of diabetic microvascular complications.

METHODS

Study participants were 71,825 DM patients who received urine dipstick test for proteinuria both in 2003-2004 and 2006-2007. They were categorized into four groups according to changes in proteinuria over 3 years (negative: negative → negative, resolved: proteinuria ≥ 1+ → negative, incident: negative → proteinuria ≥ 1+, persistent: proteinuria ≥ 1+ → proteinuria ≥ 1+). Cox-proportional hazard model was used in assessing the adjusted hazard ratios (HR) and 95% confidence interval (CI) for incidence of retinopathy, and neuropathy (adjusted HR [95% CI]).

RESULT

In all of DM patients, risk for comprehensive incidence of retinopathy and neuropathy increased in all types of proteinuria changes. In type 1 DM, HR for retinopathy and neuropathy generally increased in order of negative (reference), resolved (2.175 [1.150-4.114] and 1.335 [0.909-1.961]), incident (2.088 [1.185-3.680] and 1.753 [1.275-2.409]), and persistent proteinuria (1.314 [0.418-4.134] and 2.098 [1.274-3.455]). This pattern of relationship was similarly observed in type 2 DM for retinopathy and neuropathy: negative (reference), resolved (1.490 [1.082-2.051] and 1.164 [0.988-1.371]), incident (1.570 [1.161-2.123] and 1.291 [1.112-1.500]), and persistent proteinuria (2.309 [1.407-3.788] and 1.272 [0.945-1.712]).

CONCLUSION

Risk for diabetic retinopathy and neuropathy generally increased in order of negative, resolved, incident, and persistent proteinuria. Once manifested proteinuria was associated with the increased risk of diabetic retinopathy and neuropathy even after remission of proteinuria.

Persistent proteinuria is associated with the occurrence of cardiovascular disease: a nationwide population-based cohort study

Proteinuria is an important risk factor for cardiovascular disease (CVD) and acts as a surrogate marker of renal damage. This study aimed to determine the association between changes in proteinuria and the occurrence of CVD. In our study, 1,708,712 participants who consecutively underwent national health examinations from 2003-2004 (first period) to 2005-2006 (second period) were included. They were classified into four groups based on the presence of proteinuria at the two consecutive health examinations: (1) normal (0 → 0), (2) proteinuria-improved (participants who had improved proteinuria (+ 1 → 0, + 2 → ≤ +1 [0 or + 1], ≥ +3 → ≤ +2 [0, + 1 or + 2]), (3) proteinuria-progressed (0 → ≥ +1, + 1 → ≥ +2, + 2 → ≥ +3), and (4) proteinuria-persistent (+ 1 → +1, + 2 → +2, ≥ +3 → ≥ +3). We used a multivariate Cox proportional hazards model to assess the occurrence of CVD according to changes of presence and severity of proteinuria. During a median of 14.2 years of follow-up, 143,041 participants (event rate, 8.37%) with composite CVD were observed. Compared with the normal group, the risk of incident risk of CVD was increased according to the severity of proteinuria in each of the persistent, progressed, and improved groups (p for trend < 0.001). In a pairwise comparison, the risk of composite CVD in the improved (hazard ratio [HR]: 1.32, 95% confidence interval [CI]: 1.27-1.37), progressed (HR: 1.49, 95% CI: 1.44-1.54), and persistent groups (HR: 1.78, 95% CI: 1.64-1.94) were higher than that of the normal group. Furthermore, the improved group had a relatively lower risk of composite CVD compared to the persistent group (HR: 0.75, 95% CI: 0.69-0.83, p < 0.001). The incidence risk of composite CVD was associated with changes of presence and severity of proteinuria. Persistent proteinuria may be associated with increased risk of CVD, even compared with improved or progressed proteinuria status.

Specific Gravity Improves Identification of Clinically Significant Quantitative Proteinuria from the Dipstick Urinalysis

Key Points

Urine albumin-to-creatinine ratio and urine protein-to-creatinine ratio are frequently obtained and represent possible tools for screening for proteinuria and thus early CKD. Adding specific gravity to dipstick proteinuria improves the ability to screen patients with clinically significant proteinuria and can be used to identify patients with early CKD.

Background

CKD is often underdiagnosed during early stages when GFR is preserved because of underutilization of testing for quantitative urine albumin-to-creatinine ratio (UACR) or urine protein-to-creatinine ratio (UPCR). Semiquantitative dipstick proteinuria (DSP) on urinalysis is widely obtained but not accurate for identifying clinically significant proteinuria.

Methods

We identified all patients with a urinalysis and UACR or UPCR obtained on the same day at a tertiary referral center. The accuracy of DSP alone or in combination with specific gravity (SG) against a gold-standard UACR ≥30 mg/g or UPCR ≥0.15 g/g, characterizing clinically significant proteinuria, was evaluated using logistic regression. Models were internally validated using ten-fold cross-validation. The SG for each DSP above which significant proteinuria is unlikely was determined.

Results

Of 11,229 patients, clinically significant proteinuria was present in 4073 (36%). The area under the receiver-operating characteristic curve (95% confidence interval) was 0.77 (0.76 to 0.77) using DSP alone and 0.82 (0.82 to 0.83) in combination with SG (P < 0.001), yielding a specificity of 0.93 (SEM=0.02) and positive likelihood ratio of 9.52 (SEM=0.85). The optimal SG cutoffs to identify significant proteinuria were ≤1.0012, 1.0238, and 1.0442 for DSP of trace, 30, and 100 mg/dl, respectively. At any SG, a DSP ≥300 mg/dl was extremely likely to represent significant proteinuria.

Conclusions

Adding SG to DSP improves recognition of clinically significant proteinuria and can be easily used to identify patients with early stage CKD who may not have otherwise received a quantified proteinuria measurement for both clinical and research purposes.

Proteinuria and risk of ocular motor cranial nerve palsy: a nationwide population-based study

Understanding the association between dipstick-detected proteinuria and oculomotor cranial nerve palsy (CNP) could have significant implications for understanding the mechanism of CNP development and for developing preventive strategies against CNP development in patients with proteinuria. This study aimed to determine the relationship between dipstick-determined proteinuria and ocular motor CNP using National Sample Cohort (NSC) database from Korea's National Health Insurance Service (NHIS). A nationwide population-based cohort study was conducted using data from the NSC database of Korea's NHIS. These data were collected from 2009 to 2018. A one-year time lag was established to prevent a situation in which the causal link was inverted. Participants aged 20 years or more who were diagnosed with proteinuria in 2009 were included. Individuals with specific pre-existing CNP, missing data, and those who were newly diagnosed with CNP or who died within one year of being tested were excluded. The study population was classified into six groups according to the degree of proteinuria (negative, trace, or between 1 + and 4 +) based on the urine dipstick test. A Cox proportional hazard regression analysis was performed to determine the linkage between the degree of proteinuria and ocular motor CNP. A total of 5,807 (0.14% of subjects) with ocular motor CNP were assigned to the ocular motor CNP group and 4,047,205 subjects were assigned to the control group. After full adjustment of comorbidities, hazard ratios (HRs) for 1 + , 2 + , 3 + and 4 + proteinuria groups were 1.449 (95% confidence interval [CI] 1.244-1.687), 2.081 (1.707-2.538), 1.96 (1.322-2.904), and 3.011 (1.507-6.014), respectively, for developing ocular motor CNP compared to the proteinuria-negative group. In subgroup analysis, the HR of patients with proteinuria for the development of ocular motor CNP was higher in the younger age group (less than 40 years) (P = 0.0242) and the group with DM (P = 0.04). Our population-based cohort study demonstrated a significant association between proteinuria and the incidence of CNP, suggesting that urine protein level could be a new clinical marker for predicting the development of CNP.

The Relationship Between Sarcopenia And Proteinuria, What Do We Know?

Sarcopenia is one of the most common geriatric syndromes in the elderly. It is defined as a decrease in muscle mass and function, and it can lead to physical disability, falls, poor quality of life, impaired immune system, and death. It is known that, the frequency of sarcopenia increases in the kidney patient population compared to healthy individuals. Although it is known that kidney disease can lead to sarcopenia; our knowledge of whether sarcopenia causes kidney disease is limited. Prior studies have suggested that protein energy wasting may be a risk of de novo CKD. Proteinuria is an important manifestation of kidney disease and there is a relationship between sarcopenia and proteinuria in diabetes, geriatric population, kidney transplant, and nephrotic syndrome. Does proteinuria cause sarcopenia or vice versa? Are they both the results of common mechanisms? This issue is not clearly known. In this review, we examined the relationship between sarcopenia and proteinuria in the light of other studies.

Trace proteinuria detected via dipstick test is associated with kidney function decline and new-onset overt proteinuria: the Japan Specific Health Checkups (J-SHC) Study

BACKGROUND

Microalbuminuria is associated with mortality, cardiovascular disease, and end-stage kidney disease. The association between trace proteinuria (detected via dipstick test) and kidney outcomes is unclear.

METHODS

This nationwide longitudinal study used data from the Japan Specific Health Checkups Study conducted during 2008-2014. The frequency of trace proteinuria (detected via dipstick test) during first two visits was used as an exposure variable (TrUP 0/2, no trace proteinuria; TrUP 1/2, detected once; TrUP 2/2, detected twice), and kidney outcomes were evaluated. The association between the frequency of trace proteinuria and incidence of 1.5-fold increase in serum creatinine levels and overt proteinuria was analyzed using Cox regression analysis. Trajectories of estimated glomerular filtration rate (eGFR) were compared using a mixed-effect model.

RESULTS

Among 306,317 participants, 3188 and 17,461 developed a 1.5-fold increase in serum creatinine levels and new-onset overt proteinuria, respectively, during the median follow-up period of 36.2 months. The adjusted hazard ratio (HR) and 95% confidence interval (CI) for 1.5-fold increase in serum creatinine level in the TrUP 1/2 and TrUP 2/2 groups, compared to TrUP 0/2 group, were 1.23 (1.07-1.42) and 1.39 (1.01-1.92), respectively, and the adjusted HR (95% CI) for overt proteinuria were 2.94 (2.83-3.06) and 5.14 (4.80-5.51), respectively. The eGFR decline rates in the TrUP 1/2 and TrUP 2/2 groups were higher than that in the TrUP 0/2 group (p for interaction < 0.001).

CONCLUSIONS

Trace proteinuria (detected via dipstick test) was associated with subsequent kidney function decline and overt proteinuria in the general population.

Comparison of three spot proteinuria measurements for pediatric nephrotic syndrome: based on the International pediatric Nephrology Association 2022 Guidelines

BACKGROUND

Pediatric nephrotic syndrome (NS) requires routine proteinuria monitoring, which is costly and affects patients' quality of life. The gold-standard 24-h urine protein (UP) measurement is challenging in children, and first-morning urine collection requires specific conditions, making it difficult in outpatient settings. Studies have reported comparability of second or random morning urine sample to the first-morning specimen. This study aimed to compare outcomes of random morning proteinuria measurements to 24-h UP and the roles of the urinary protein creatinine ratio (UPCR) and dipstick tests in pediatric NS, based on International Pediatric Nephrology Association (IPNA) 2022 Guidelines.

METHOD

Twenty-four-hour and morning urine samples were collected from 92 pediatric NS patients. These were subjected to automated analyses for 24-h UP, UPCR, and semi-automated dipstick analysis. A blinded doctor performed manual dipstick analysis.

RESULTS

UPCR had a stronger correlation with 24-h UP than with automated and manual urine dipstick tests. UPCR had the highest sensitivity and specificity for predicting no remission/relapse and high sensitivity but low specificity for complete remission. The optimal UPCR cutoff for remission was 0.44 mg/mg and for no remission/relapse was 2.08 mg/mg. Automated and manual dipstick tests demonstrated limited sensitivity but high specificity and similar AUC values for remission/relapse.

CONCLUSION

UPCR was sensitive and specific for diagnosing no remission/relapse and sensitive but not specific for detecting remission. Manual and automated urine dipstick tests were comparable for remission and no remission/relapse detection. This study supports the IPNA 2022 Guidelines, as 2 mg/mg was the optimal UPCR cutoff for no remission/relapse, while for remission the optimal cutoff was 0.4 mg/mg.

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.

The risk of Parkinson's disease according to diabetic kidney disease status in a Korean population

INTRODUCTION

Type 2 diabetes is a risk factor for Parkinson's disease (PD). Recently, it has been reported that proteinuria without reduced estimated glomerular filtration rate (eGFR) can increase the risk of PD development. The objective of this study was to evaluate the risk of PD among Korean adults with type 2 diabetes stratified by proteinuria (PU) and eGFR levels.

METHODS

Using the Korean National Health Insurance Service database, a total of 2,217,326 patients with type 2 diabetes who underwent regular health check-ups from 2009 to 2012 were included. These patients were classified into four groups (no-diabetic kidney disease (DKD) (PU^-GFR^-), proteinuric DKD with normal eGFR (PU⁺GFR^-), nonproteinuric DKD (PU^-GFR⁺), and proteinuric DKD with reduced eGFR (PU⁺GFR⁺) and followed up until 2018. PD was defined using International Classification of Diseases, 10th revision.

RESULTS

The prevalence of PU^-GFR^-, PU⁺GFR^-, PU^-GFR⁺, or PU⁺GFR⁺ phenotype was 83.3%, 5.0%, 10.1%, or 1.6%, respectively. During a median follow-up of 7.2 years, 16,079 participants developed PD. Hazard ratios for PD were 1.10 (95% confidence interval [CI]: 1.01-1.21, p = 0.0091), 1.15 (95% CI: 1.09-1.21, p < 0.0001), and 1.23 (95% CI: 1.09-1.39, p < 0.0001) for participants in PU⁺GFR^-, PU^-GFR⁺, and PU⁺GFR⁺ groups relative to those in the PU^-GFR^- group, respectively. Effects of DKD on PD were more pronounced in those aged less than 65 years.

CONCLUSION

Reduced eGFR and/or proteinuria might be independent risk factors for boosting PD development among patients with type 2 diabetes. More attention should be paid to PD in patients with DKD, even in a younger aged population.

Association of Longitudinal Trajectories of Insulin Resistance With Adverse Renal Outcomes

OBJECTIVE

To analyze the relationship between time-serial changes in insulin resistance and renal outcomes.

RESEARCH DESIGN AND METHODS

A prospective cohort of subjects from the general population without chronic kidney disease (CKD) underwent a biennial checkup for 12 years (n = 5,347). The 12-year duration was divided into a 6-year exposure period, where distinct HOMA for insulin resistance (HOMA-IR) trajectories were identified using latent variable mixture modeling, followed by a 6-year event accrual period, from which the renal outcome data were analyzed. The primary end point was adverse renal outcomes, defined as a composite of estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 in two or more consecutive checkups or albumin ≥1+ on urine strip.

RESULTS

Two distinct groups of HOMA-IR trajectories were identified during the exposure period: stable (n = 4,770) and increasing (n = 577). During the event accrual period, 449 patients (8.4%) developed adverse renal outcomes, and the risk was higher in the increasing HOMA-IR trajectory group than in the stable group (hazard ratio 2.06, 95% CI 1.62-2.60, P < 0.001). The results were similar after adjustment for baseline clinical characteristics, comorbidities, anthropometric and laboratory findings, eGFR, and HOMA-IR. The clinical significance of increasing HOMA-IR trajectory was similar in three or four HOMA-IR trajectories. The increasing tendency of HOMA-IR was persistently associated with a higher incidence of adverse renal outcomes, irrespective of the prevalence of diabetes.

CONCLUSIONS

An increasing tendency of insulin resistance was associated with a higher risk of adverse renal outcomes. Time-serial tracking of insulin resistance may help identify patients at high risk for CKD.

Urinary Dipstick Is Not Reliable as a Screening Tool for Albuminuria in the Emergency Department—A Prospective Cohort Study

Albuminuria is a sensitive marker for renal dysfunction. Urinary dipstick tests are frequently used to screen for urinary abnormalities in the emergency department (ED). The aim of this prospective cohort study is to evaluate the usefulness of urinary dipstick testing as a screening tool for albuminuria in the ED setting and to determine the persistency of albuminuria identified in the acute setting. Urinary dipstick tests and spot urine samples were obtained simultaneously for analysis of the urinary albumin-creatinine ratio (ACR). Participants with positive dipsticks for protein were invited for a second urinalysis four to six weeks after admission. The study included 234 patients admitted to the ED. Urinalysis was performed on 178 patients of which 46% (n = 82) had positive urinary dipstick tests for proteinuria. The sensitivity and specificity of the dipstick test were low (72.7% and 55.7% respectively) when compared to the ACR. Of the 82 patients with positive dipsticks at admission, 35 were available for follow-up. We observed a significant reduction in ACR at follow-up when compared to ACR at admission (p = 0.004). This paper concludes that urinary dipstick tests are not a reliable means to screen for albuminuria in the ED setting.

Association of proteinuria and hypertension with incident atrial fibrillation in an elderly population: nationwide data from a community-based elderly cohort

OBJECTIVE

The excess risk of atrial fibrillation in relation to the presence of proteinuria associated with hypertension has not been well elucidated. We aimed to determine the effect of hypertension and/or proteinuria on the incidence of atrial fibrillation. Second, we evaluated whether the associations with temporal changes in proteinuria status on the incidence of atrial fibrillation.

METHODS AND RESULTS

A total of 85 434 participants with hypertension and 125 912 participants without hypertension with age at least 60 years from the Korea National Health Insurance Service-Senior cohort were included. Amongst controls (participants without proteinuria and hypertension), hypertension only, proteinuria only, and hypertension with proteinuria groups, the adjusted incidences of atrial fibrillation were 0.51, 0.69. 0.78 and 0.99 per 100 person-years, respectively after inverse probability of treatment weighting. Compared with controls, the weighted risks of atrial fibrillation in the hypertension only, proteinuria only and hypertension with proteinuria groups were increased by 37% (hazard ratio 1.37, 95% confidence interval, CI 1.30-1.44, P = 0.001), 55% (hazard ratio 1.55, 95% CI 1.28-1.88, P < 0.001), and 98% (hazard ratio 1.98, 95% CI 1.62-2.43, P < 0.001), respectively. Populations who had proteinuria in the first examination had an increased risk of atrial fibrillation even in the group whereby the proteinuria was resolved on the second examination (hazard ratio 1.36, 95% CI 1.12-2.31, P < 0.001). The presence of proteinuria in first and second analysis had the highest risk of incident atrial fibrillation (hazard ratio 1.61, 95% CI 1.12-2.31).

CONCLUSION

In conclusion, hypertension and/or proteinuria were associated with increased risk of atrial fibrillation, with the greatest risks when both are present. Proteinuria could be a useful factor for predicting atrial fibrillation development.

Relationship between chronic kidney disease and sarcopenia

Few studies have investigated the relationship between sarcopenia and mild to moderate renal decline. This study aimed to investigate the relationship between chronic kidney disease (CKD) and sarcopenia. In total, 123 patients hospitalized with CKD and 57 healthy volunteers who underwent physical examination during the same period (control group) were analyzed. Body compositions were measured by dual-energy X-ray absorptiometry, and the relative appendicular skeletal muscle index (RASMI) was calculated. Muscular strength was evaluated using hydraulic hand dynamometer. Walking speed within 6 m was measured for muscular function assessment. Single-photon emission computed tomography was performed to measure the glomerular filtration rate of CKD patients, who were then divided into CKD1 (55 patients in CKD stages 1 and 2) and CKD2 (68 patients in CKD stages 3-5). RASMI showed a downward trend with CKD progression (P = 0.001). Multivariate logistic regression analysis showed that age and CKD progression were independent risk factors for sarcopenia. The morbidity of sarcopenia was significantly greater in CKD patients than in healthy volunteers, and the degree of muscle loss was closely related to CKD progression.

Effect of Psychosocial Distress on the Rate of Kidney Function Decline

BACKGROUNDS

Chronic kidney disease is a growing global health problem. Psychosocial stress has been found to induce changes in biological processes and behavioral patterns that increase risks of cardiovascular and metabolic diseases. However, the association between psychosocial stress and kidney function is not well understood.

OBJECTIVE

To evaluate the association between psychosocial stress and kidney function decline.

DESIGN

In this prospective cohort study, psychosocial distress was assessed using the psychosocial well-being index short-form (PWI-SF).

PARTICIPANTS

Data of a total of 7246 participants were retrieved from a community-based cohort (Korean Genome and Epidemiology Study).

MAIN MEASURES

The rate of estimated glomerular filtration rate (eGFR) decline was calculated for each individual. Rapid eGFR decline was defined as a decrease of ≥ 3 mL/min/1.73 m² per year. The presence of kidney disease was defined as eGFR < 60 mL/min/1.73 m² at baseline or proteinuria of higher than trace levels from two consecutive urine test results.

KEY RESULTS

A total of 7246 participants were analyzed. The mean eGFR was 92.1 ± 14.0 mL/min/1.73 m². Rapid eGFR decline was observed in 941 (13.0%) participants during a median follow-up of 11.7 years. When the participants were categorized into tertiles according to PWI-SF score, rapid eGFR decline was more prevalent in the group with the highest PWI-SF score (15.8%) than in the group with the lowest score (12.2%). Multivariate logistic regression analysis revealed that the risk of rapid eGFR decline was significantly increased in the tertile group with the highest PWI-SF score compared to the lowest group (odds ratio, 1.35; 95% confidence interval, 1.15-1.59). This association was maintained even after adjusting for confounding variables and excluding participants with kidney disease.

CONCLUSIONS

Higher levels of psychosocial distress were closely associated with an increased risk of rapid kidney function decline.

Association of proteinuria and incident atrial fibrillation in patients with diabetes mellitus: a population-based senior cohort study

Diabetes mellitus (DM) is considered an independent risk factor for atrial fibrillation (AF). The excess risk in relation to the presence of proteinuria has not been well elucidated. Our aim was to determine the association between the incidence of AF and proteinuria in diabetic population. A total of 240,499 individuals aged ≥ 60 years from the Korea National Health Insurance Service-Senior cohort from 2004 to 2014 were included. 4.2% of individuals with DM and 3.7% of controls were diagnosed with AF during a median follow-up period of 7.2 years. Amongst controls (participants without proteinuria and DM), DM only, proteinuria only, and DM with proteinuria groups, the crude incidences of AF were 0.58, 0.70, 0.96, 1.24 per 100 person-years respectively. Compared with controls, the weighted risk of AF was increased by 11% (hazard ratio = 1.11, 95% confidence interval = 1.02-1.20, P = .001), 48% (hazard ratio = 1.48, 95% confidence interval = 1.30-1.69, P < .001), and 66% (hazard ratio = 1.66, 95% confidence interval = 1.26-2.18, P < .001) in the DM only, proteinuria only, and DM with proteinuria groups, respectively (P for trend < .001). Degree of proteinuria in diabetic patients was associated with a significantly higher rate of incident AF in dose dependent manner. Thus, assessing proteinuria by a simple urine dipstick test could provide a useful adjunct to risk assessment for AF in elderly population with DM.

Dipstick proteinuria and risk of type 2 diabetes mellitus: a nationwide population-based cohort study

Background

Proteinuria has been recognized as a marker of systemic inflammation and endothelial dysfunction associated with insulin resistance and β-cell impairment, which can contribute to the development of type 2 diabetes mellitus (T2DM). However, it is unknown whether the dipstick proteinuria test has a predictive value for new-onset T2DM.

Methods

This retrospective cohort study analyzed 239,287 non-diabetic participants who participated in the Korean nationwide health screening program in 2009–2010. Proteinuria was determined by the urine dipstick test at the baseline health screening. We performed multivariate Cox proportional regression analyses for the development of new-onset T2DM. Follow-up was performed until December 2015.

Results

During the mean follow-up period of 5.73 years, 22,215 participants were diagnosed with new-onset T2DM. The presence of proteinuria was significantly associated with an increased risk of T2DM (adjusted hazard ratio: 1.19, 95% confidence interval: 1.10, 1.29). There was a positive dose–response relationship between the degree of dipstick proteinuria and T2DM risk. This significant association between proteinuria and T2DM risk was consistent regardless of the fasting glucose level at baseline.

Conclusions

Dipstick proteinuria is a significant risk factor for new-onset T2DM. Therefore, proteinuria might be a useful biomarker to identify those at a high risk for developing T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02934-y.

Healthy lifestyle reduces incidence of trace/positive proteinuria and rapid kidney function decline after 2 years: from the Japan Ningen Dock study

BACKGROUND

Lifestyle modification is recommended for subjects with trace proteinuria during health checkups. However, whether overall healthy lifestyle reduces the incidence of trace/positive proteinuria or rapid decline in estimated glomerular filtration rate (eGFR) is not clarified.

METHODS

A total of 451 534 people (277 494 men and 174 040 women) ages 20-79 years with negative proteinuria were included. The number of three healthy lifestyle factors (LFs) was assessed: noncurrent smoking, healthy eating habits (late dinner, snacking and skipping breakfast <3 times/week) and body mass index <25. The incidence of trace (±) and positive (≥1+) proteinuria by the dipstick method and eGFR decline ≥20% over 2 years were compared with the number of healthy LFs.

RESULTS

The incidence of trace/positive proteinuria and rapid eGFR decline decreased with an increasing number of healthy LFs as follows: odds ratios (ORs) for trace proteinuria, 0.91 [95% confidence interval (CI) 0.86-0.96], 0.82 (0.78-0.87) and 0.72 (0.68-0.77); ORs for positive proteinuria, 0.76 (95% CI 0.67-0.86), 0.56 (0.50-0.63) and 0.46 (0.40-0.53); and ORs for an eGFR decline ≥20%, 0.93 (95% CI 0.82-1.05), 0.90 (0.79-1.02) and 0.81 (0.70-0.93) for those with one, two and three healthy LFs compared with those with none of the three healthy LFs, respectively. Overall, subjects with a healthy lifestyle showed 28, 54 and 19% reduced risk of developing trace proteinuria, positive proteinuria and eGFR decline ≥20%, respectively, compared with those with an unhealthy lifestyle after 2 years. This association was similarly observed even among subjects without hypertension (HT) or diabetes mellitus (DM).

CONCLUSIONS

Subjects with an overall healthy lifestyle showed a lower incidence of trace/positive proteinuria by dipstick test and rapid eGFR decline over 2 years in a nationwide general population. Thus lifestyle modification should be recommended for subjects with trace proteinuria during health checkups, even for subjects without HT or DM.

Impact of nutritional index on contrast-associated acute kidney injury and mortality after percutaneous coronary intervention

The risk of malnutrition in acute kidney injury and mortality in coronary artery disease patients has not been studied. This study aimed to evaluate whether nutritional status assessed by Onodera's prognostic nutritional index (PNI) was related to percutaneous coronary intervention (PCI) outcomes. A total of 3731 patients who received PCI between January 2010 and December 2018 were included. The relationship between PNI at the time of PCI and the occurrence of contrast-associated acute kidney injury (AKI) and all-cause death was evaluated using logistic regression and Cox proportional hazards models, respectively. AKI occurred in 271 patients (7.3%). A low PNI was independently associated with an increased risk of AKI on multivariate logistic regression analysis (OR 0.96, 95% CI 0.94-0.98, P = 0.001). During the median follow-up of 4.3 years, Kaplan-Meier analysis showed that patients with AKI/low PNI < 47.8 had a higher death rate. After adjusting for various risk factors, a low PNI was a significant risk factor for mortality (HR 0.98, CI 0.96-0.99, P = 0.003). A low level of PNI was associated with increased mortality, especially in the group aged over 70 years and female sex. PNI was closely associated with acute kidney outcomes and patient mortality after PCI.

Proteinuria Is Associated with the Development of Crohn's Disease: A Nationwide Population-Based Study

BACKGROUND AND AIMS

The impact of proteinuria and its severity on the incidence of inflammatory bowel disease (IBD) has not yet been studied. We aimed to determine the association between proteinuria measured by urine dipstick tests and the development of IBD.

METHODS

This nationwide population-based study was conducted using the Korean National Health Insurance Service (NHIS) database. A total of 9,917,400 people aged 20 years or older who had undergone a national health examination conducted by the NHIS in 2009 were followed up until 2017. The study population was classified into four groups-negative, trace, 1+, and ≥ 2+-according to the degree of proteinuria measured by the urine dipstick test. The primary endpoint was newly diagnosed IBD, Crohn's disease (CD), or ulcerative colitis (UC) during the follow-up period.

RESULTS

Compared with the dipstick-negative group, the incidence of CD significantly increased according to the degree of proteinuria (adjusted hazard ratio [aHR] with 95% confidence interval [CI], 1.01 [0.703-1.451], 1.515 [1.058-2.162], and 2.053 [1.301-3.24] in the trace, 1+, and ≥ 2+ dipstick groups, respectively; p for trend 0.007). However, there was no significant difference in the incidence of UC according to the degree of proteinuria (aHR with 95% CI, 1.12 [0.949-1.323], 0.947 [0.764-1.174], and 1.009 [0.741-1.373] in the trace, 1+, and ≥ 2+ dipstick groups, respectively; p for trend 0.722). In the subgroup analysis, dipstick-positive proteinuria independently increased the incidence of CD regardless of the subgroup. However, dipstick-positive proteinuria was associated with the risk of UC in those with diabetes mellitus and not in those without diabetes mellitus (aHR, 1.527 vs. 0.846; interaction p-value 0.004). The risk of CD was increased or decreased according to proteinuria changes but not associated with the risk of UC.

CONCLUSION

Proteinuria, measured by the dipstick test, is strongly associated with the development of CD.

Diagnostic accuracy of a urine dipstick for detecting albuminuria in hypertensive patients

Background: Screening for albuminuria is generally recommended among patients with hypertension. While the urine dipstick is commonly used for screening urine albumin, there is little evidence about its diagnostic accuracy among these patients in Thailand. This study aimed to assess the diagnostic accuracy of a dipstick in Thai hypertensive patients for detecting albuminuria. Methods: This study collected the data of 3,067 hypertensive patients, with the results of urine dipstick and urine albumin-to-creatinine ratio (ACR) from random single spot urine being examined in the same day at least once, at Lampang Hospital, Thailand, during 2018. For ACR, a reference standard of ≥ 30 mg/g was applied to indicate the presence of albuminuria. Results: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value of the trace result from dipsticks were 53.6%, 94.5%, 86.5%, and 75.5%, respectively. The area under the receiver operating characteristic curve of the dipstick was 0.748. Conclusion: Using the dipstick for screening albuminuria among hypertensive patients should not be recommended for mass screening due to its low sensitivity. In response to high PPV, a trace threshold of the dipstick may be used to indicate presence of albuminuria.

Diagnostic accuracy of a urine dipstick for detecting albuminuria in hypertensive patients

Background: Screening for albuminuria is generally recommended among patients with hypertension. While the urine dipstick is commonly used for screening urine albumin, there is little evidence about its diagnostic accuracy among these patients in Thailand. This study aimed to assess the diagnostic accuracy of a dipstick in Thai hypertensive patients for detecting albuminuria. Methods: This study collected the data of 3,067 hypertensive patients, with the results of urine dipstick and urine albumin-to-creatinine ratio (ACR) from random single spot urine being examined in the same day at least once, at Lampang Hospital, Thailand, during 2018. For ACR, a reference standard of ≥ 30 mg/g was applied to indicate the presence of albuminuria. Results: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value of the trace result from dipsticks were 53.6%, 94.5%, 86.5%, and 75.5%, respectively. The area under the receiver operating characteristic curve of the dipstick was 0.748. Conclusion: Using the dipstick for screening albuminuria among hypertensive patients should not be recommended for mass screening due to its low sensitivity. In response to high PPV, a trace threshold of the dipstick may be used to indicate presence of albuminuria.

Diagnostic accuracy of a urine dipstick for detecting albuminuria in hypertensive patients

Background: Screening for albuminuria is generally recommended among patients with hypertension. While the urine dipstick is commonly used for screening urine albumin, there is little evidence about its diagnostic accuracy among these patients. This study aimed to assess the diagnostic accuracy of a dipstick in Thai hypertensive patients for detecting albuminuria. Methods: This study collected the data of 3,067 hypertensive patients, with the results of urine dipstick and urine albumin-to-creatinine ratio (ACR) from random single spot urine being examined in the same day at least once, at Lampang Hospital, Thailand, during 2018. For ACR, a reference standard of ≥ 30 mg/g was applied to indicate the presence of albuminuria. Results: The sensitivity, specificity, positive predictive value (PPV), and negative predictive value of the trace result from dipsticks were 53.6%, 94.5%, 86.5%, and 75.5%, respectively. The area under the receiver operating characteristic curve of the dipstick was 0.748. Conclusion: Using the dipstick for screening albuminuria among hypertensive patients should not be recommended due to its low sensitivity. In response to high PPV, a trace threshold of the dipstick may be used to indicate presence of albuminuria.

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.

Association of proteinuria with incident atrial fibrillation in the general Japanese population

BACKGROUND

Although proteinuria has been associated with incident atrial fibrillation (AF) in Western countries, the association has not been investigated in the general Japanese population.

METHODS

Participants aged ≥40 years who underwent the Japanese specific health check-up in Kanazawa City in 2013 and who completed a urine dipstick test were included in this study. Exposure was considered as presence or absence of proteinuria (≥1+). The outcome was incident AF confirmed by 12-lead electrocardiography. The Cox proportional hazard model was used to compute hazard ratio (HR) of proteinuria (≥1+) for incident AF after adjustment for traditional risk factors. We also completed stratified analyses by baseline characteristics.

RESULTS

A total of 37,910 participants aged ≥40 years were included (mean age: 72.3 years, male sex: 37%). Proteinuria ≥1+ was observed in 2.765 (7.3%) participants. During a median follow-up period of 5 years, 708 incident AF cases were observed. Proteinuria ≥1+ was associated with incident AF (HR, 1.47: 95% confidence interval, 1.18-1.84) after covariate adjustment. Stratified analysis demonstrated that the association of proteinuria with AF was stronger in participants <75 years [HR 1.89 (95% CI 1.32-2.70)] compared with those ≥75 years [HR 1.27 (95% CI 0.95-1.69)] (interaction p-value=0.02).

CONCLUSIONS

Proteinuria was significantly associated with incident AF in the general Japanese population. The evaluation of proteinuria using urine dipstick test may be useful in the evaluation of incident AF, especially in younger general population.

Association of Single Measurement of dipstick proteinuria with physical performance of military males: the CHIEF study

BACKGROUND

Proteinuria, a marker of kidney injury, may be related to skeletal muscle loss. Whether the severity of proteinuria is associated with physical performance is unclear.

METHODS

We examined the association of proteinuria severity with physical performance cross-sectionally in 3357 military young males, free of chronic kidney disease, from the cardiorespiratory fitness and hospitalization events in armed Forces (CHIEF) study in Taiwan. The grades of proteinuria were classified according to one dipstick urinalysis which were collected at morning after an 8-h fast as unremarkable (0, +/-, and 1+), moderate (2+) and severe (3+ and 4+). Aerobic physical performance was evaluated by time for a 3000-m run and anaerobic physical performance was evaluated by numbers of 2-min sit-ups and 2-min push-ups, separately. Multiple linear regressions were used to determine the relationship.

RESULTS

As compared with unremarkable proteinuria, moderate and severe proteinuria were dose-dependently correlated with 3000-m running time (β: 4.74 (95% confidence intervals (CI): - 0.55, 10.02) and 7.63 (95% CI: 3.21, 12.05), respectively), and inversely with numbers of 2-min push-ups (β = - 1.13 (- 1.97, - 0.29), and - 1.00 (- 1.71, - 0.28), respectively) with adjustments for age, service specialty, body mass index, blood pressure, alcohol intake, smoking, fasting plasma glucose, blood urea nitrogen, serum creatinine and physical activity. However, there was no association between proteinuria severity and 2-min sit-ups.

CONCLUSIONS

Our findings show a relationship of dipstick proteinuria with aerobic physical performance and parts of anaerobic physical performance in military healthy males. This mechanism is not fully understood and requires further investigations.

Chronic Kidney Disease Increases the Risk of Hip Fracture: A Prospective Cohort Study in Korean Adults

This study was conducted to examine the association between renal function and hip fracture. We followed up 352,624 Korean adults, who participated in health examinations during 2009-2010 until 2013. Kidney function was assessed by creatinine-based estimated glomerular filtration rate (eGFR) and albuminuria using urine reagent strip results. The incidence of hip fracture was examined by hospital discharge records. Hazard ratios (HRs) for hip fracture were calculated using Cox proportional hazard models after adjusting for multiple confounders. During a mean follow-up of 4.0 years, 1177 participants suffered a hip fracture. Lower eGFR and more severe albuminuria were associated with a higher risk of hip fracture. The HRs for hip fracture were 1.89 (95% confidence interval [CI] 1.47-2.43) and 3.75 (95% CI 2.30-6.11) among participants with eGFRs of 30 to 44 and 15 to 29 mL/min/1.73m² relative to those with an eGFR ≥60 mL/min/1.73m² , respectively. The HRs were 1.30 (95% CI 1.02-1.65) for moderate albuminuria and 1.58 (95% CI 1.07-2.35) for severe albuminuria (p for trend = 0.002). Participants with albuminuria had a higher risk of hip fracture than those without albuminuria, even when they belonged to the same eGFR category (HR = 1.75 versus 3.30 for an eGFR of 30 to 44 mL/min/1.73m² ; HR = 2.72 versus 7.84 for an eGFR of 15 to 29 mL/min/1.73m² ). The effects of each 10 mL/min/1.73m² decrease in eGFR were stronger with advancing albuminuria severity (p_interaction = 0.016). In conclusion, both low eGFR and albuminuria were risk factors for incident hip fracture in Korean adults. Moreover, these factors exerted a synergistic effect on the risk of hip fracture. © 2020 American Society for Bone and Mineral Research.

Prevalence of kidney damage in Chinese elderly: a large-scale population-based study

BACKGROUND

In China, both population aging and kidney damage has become emerging public health challenges. Despite the number of elders is huge, data on kidney damage in this population are scarce. The present study aimed to describe the prevalence of kidney damage among older adults in Wuhan, China.

METHODS

To describe the prevalence of kidney damage among Chinese elderly, the health screening data of 350,881 adults older than 65 years in Wuhan, China were collected and analyzed. Kidney damage was defined as eGFR less than 60 mL/min per 1·73 m2 or the presence of proteinuria. Decreased renal function was defined as an eGFR < 60 mL/min/1.73 m2. Proteinuria was defined as urine protein ≥1+ and without urine WBC or nitrite positive. The associated risk factors of eGFR decline and kidney damage were analyzed by multivariate logistic regression.

RESULTS

The age-standardized prevalence of kidney damage, decreased renal function and proteinuria was 17.2, 13.5 and 5.3%. Among the patients, up to 74.4% was stage 3. The prevalence of kidney damage and eGFR decline were higher in suburbs than in urban (18.3% vs 16.0 and 14.6% vs 12.4%). Factors independently associated with kidney damage were age, female, BMI, abdominal circumference, hypertension, diabetes, stroke and coronary heart disease.

CONCLUSIONS

Kidney damage has become an important public health problem in Chinese elderly. More attention should be paid to elderly lived in suburbs or rural area in our further work.

Proteinuria impacts patient survival differentially based on clinical setting: A retrospective cross-sectional analysis of cohorts from a single health system: Retrospective cohort study

Background

Chronic kidney disease (CKD) staging is improved by adding proteinuria to glomerular filtration rate (GFR). While proteinuria independently predicts CKD progression and mortality, the clinical setting of proteinuria determination has not been well-studied previously. The objective of our study is to determine whether clinical setting differentially impacts survival outcomes.

Methods

Kaplan-Meier and Cox proportional hazards analyses of overall survival were performed retrospectively for cohorts of outpatients (n = 22,918), emergency patients (n = 16,861), and inpatients (n = 12,304) subjected to urinalysis (UA) at a single health system in 2010. GFR (G1-G5) and proteinuria (A1:<30 mg, A2:30–300 mg, A3:>300 mg) were classified under Kidney Disease: Improving Global Outcomes (KDIGO) guidelines.

Results

GFR and proteinuria levels varied more in inpatients than in emergency and outpatients. For each clinical population, survival significantly decreased with increasing proteinuria (A1>A2>A3, p < 0.05 for each comparison). The effect of proteinuria on survival differed by clinical setting, with statistical differences in all categories other than A3 in outpatients and emergency patients (p = 0.98). The strongest predictors of mortality were cancer diagnosis (HR: 3.07, p < 0.0001) and very-high KDIGO classification (HR: 2.01, p < 0.0001). Limitations include the retrospective observational study design and single health system analysis.

Conclusions

The value of UA to screen for proteinuria in each clinical setting is evident, but the impact of A2 and A3 level proteinuria on survival varies depending on the clinical scenario in which the determination was made. The clinical setting of proteinuria measurement should be factored into both patient care and clinical research activities.

•

Proteinuria and GFR independently predict survival in inpatients, ED and outpatients.

•

The effect of proteinuria on survival differs by clinical setting.

•

Hospitalized patients have lower survival rates than emergency and outpatients.

•

Clinical setting of proteinuria should be considered in patient care and research.

Chronic renal dysfunction, proteinuria, and risk of Parkinson's disease in the elderly

BACKGROUND

The roles of chronic kidney disease and proteinuria in the development of Parkinson's disease have not been widely studied. The objective of this study was to examine the associations of chronic renal dysfunction and proteinuria with the risk of PD in older adults using cohort data of the whole South Korean population.

METHODS

We included 3,580,435 individuals aged ≥65 years who had undergone health checkups provided by the National Health Insurance Service of South Korea between 2009 and 2012 and were followed until 2015. Multivariable Cox proportional hazards regression models were performed.

RESULTS

During a mean follow-up of 5.2 ± 1.3 years, 30,813 individuals (0.86% of the total population) developed PD. Lower estimated glomerular filtration rate and a higher degree of proteinuria on a dipstick test were associated with higher incidence probability of PD (log-rank P < 0.001). In Cox regression models, chronic renal dysfunction graded by estimated glomerular filtration rate (mL/min/1.73 m² ) was associated with increased risk of PD after adjusting for potential confounding variables; hazard ratio (95% confidence interval) was 1.13 (1.10-1.17) for estimated glomerular filtration rate 60-90, 1.36 (1.31-1.42) for estimated glomerular filtration rate 30-60, and 1.47 (1.32-1.63) for estimated glomerular filtration rate <30 (P for trend <0.001). Proteinuria ≥1+ was also associated with increased risk of PD development (hazard ratio, 1.12; 95% confidence interval, 1.06-1.18). Coexistence of chronic kidney disease and proteinuria showed an increased hazard ratio of 1.33 (95% confidence interval, 1.23-1.45) for PD occurrence.

CONCLUSIONS

Our findings suggest that chronic renal dysfunction and dipstick-positive proteinuria may be independent risk factors for the development of PD in older adults. © 2019 International Parkinson and Movement Disorder Society.

Low-normal hemoglobin levels and anemia are associated with increased risk of end-stage renal disease in general populations: A prospective cohort study

Background

The impact of low-normal hemoglobin (Hb) levels and anemia on the risk of end-stage renal disease (ESRD) in general populations has rarely been examined.

Methods

510,620 Korean adults aged 40–80 years without known chronic kidney disease (CKD) underwent health examinations during 2002–2003 and were followed-up until 2013. Incidence of ESRD was identified by hospital discharge and clinical visit records.

Results

During a mean follow-up of 10.5, 575 women and 1047 men were diagnosed with ESRD. Lower Hb levels were associated with an increased risk of ESRD at given severity of albuminuria and at given estimated glomerular filtration rate (eGFR). Hb 13–13.9 g/dL in men, Hb 11–11.9 g/dL in women, and trace albuminuria assessed by dipstick urinalysis were associated with more than doubled risk. The risk associated with lower Hb was stronger in older (≥60 years) than younger women. Among 349,993 participants with information on eGFR, the multivariable-adjusted HRs associated with 1 g/dL lower Hb in participants with eGFR values ≥60, 30–59, and <30 mL/min/1.73 m² were 1.34 (95% CI, 1.17–1.54), 1.55 (1.38–1.74), and 1.75 (1.47–2.09), respectively (Pinteraction between eGFR groups = .06).

Conclusions

Low-normal Hb levels and anemia are risk factors for ESRD incidence in person without CKD and for CKD progression to ESRD. Lower Hb increases the risk of ESRD through synergistic biological interactions with lower eGFR and albuminuria. The impacts of lower Hb may be stronger in older than younger women. Proper management and screening at earlier stage of Hb decline and anemia might reduce the burden of CKD.

Hepatitis B virus infection and development of chronic kidney disease: a cohort study

Background

The effect of chronic hepatitis B virus (HBV) infection on the risk of chronic kidney disease (CKD) is controversial. We examined the prospective association between hepatitis B surface antigen (HBsAg) serology status and incident CKD in a large cohort of men and women.

Methods

Cohort study of 299,913 adults free of CKD at baseline who underwent health screening exams between January 2002 and December 2016 in South Korea. Incident CKD was defined as the development of an estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73m² and/or proteinuria.

Results

Over 1,673,701 person-years of follow-up, we observed 13,924 incident cases of CKD (3225 cases of eGFR < 60 ml/min/1.73m² and 11,072 cases of proteinuria). In fully adjusted models comparing positive to negative HBsAg participants, the hazard ratio (HR, 95% confidence interval) for incident CKD was 1.11 (1.03–1.21; P = 0.01). The corresponding HR for incident proteinuria and for eGFR < 60 ml/min/1.73m² were 1.23 (1.12–1.35; P <  0.001) and 0.89 (0.73–1.07; P = 0.21), respectively. The associations were similar across categories of liver enzyme levels at baseline.

Conclusion

In this large cohort, HBsAg positive serology was associated with higher risk of incident CKD, and we provide novel evidence that this association was due to a higher incidence of proteinuria in HBsAg positive participants. Our study adds to the growing body of evidence suggesting that chronic HBV infection may be a contributor to the increasing incidence of CKD.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1154-4) contains supplementary material, which is available to authorized users.

A Passive Mixing Microfluidic Urinary Albumin Chip for Chronic Kidney Disease Assessment

Urinary albumin level is an important indicator of kidney damage in chronic kidney disease (CKD) but effective routine albumin detection tools are lacking. In this paper, we developed a low-cost and high accuracy microfluidic urinary albumin chip (UAL-Chip) to rapidly measure albumin in urine. The UAL-Chip offers three major features: (1) we incorporated a fluorescent reaction assay into the chip to improve the detection accuracy; (2) we constructed a passive and continuous mixing module in the chip that provides user-friendly operation and greater signal stability; (3) we applied a pressure-balancing strategy based on the immiscible oil coverage that achieves precise control of the sample-dye mixing ratio. We validated the UAL-Chip using both albumin standards and urine samples from 12 CKD patients and achieved an estimated limit of detection (LOD) of 5.2 μg/mL. The albumin levels in CKD patients' urine samples measured by UAL-Chip is consistent with the traditional well-plate measurements and clinical results. We foresee the potential of extending this passive and precise mixing platform to assess various disease biomarkers.

Proteinuria is an independent predictor of rapid progression of mild to moderate aortic stenosis in patients with preserved renal function

Although proteinuria is a well-known risk factor for cardiovascular disease, its relationship with the progression of aortic stenosis (AS) has not been established. Our aim was to investigate the relationship between proteinuria (detected by urine dipstick test) and AS progression (assessed by the annualized reduction rate of aortic valve area [AVA]). A total of 460 patients with mild to moderate AS (defined by a peak velocity of 2.0-4.0 m/s) without end-stage renal disease who underwent two echocardiograms at least 3 months apart were included. The progression of AS was significantly faster in patients with proteinuria than those without (108 patients vs. 352 patients; annualized reduction rate of AVA, - 7.7 ± 13.5% vs. - 4.5 ± 11.6%; p = 0.017). The relationship between the presence of proteinuria and the accelerated progression of AS was significant among patients with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² (- 11.0 ± 17.5% vs. - 4.2 ± 10.0%; p < 0.001), but not among those with eGFR 15-60 mL/min/1.73 m² (- 5.8 ± 10.3 vs. - 5.3 ± 14.8%; p = 0.822). When stratified by the presence of diabetes, the association of proteinuria with AS progression was only significant in patients without diabetes (- 8.1 ± 12.0% vs. - 8.1 ± 15.7%; p = 0.018). Multivariable logistic regression analysis identified that the presence of proteinuria was an independent predictor of AS progression. The progression of AS was accelerated in patients with mild to moderate AS and proteinuria, particularly among those with preserved renal function and no diabetes.

Association Between Preoperative Proteinuria and Postoperative Acute Kidney Injury and Readmission

Importance

Proteinuria indicates renal dysfunction and is a risk factor for morbidity among medical patients, but less is understood among surgical populations. There is a paucity of studies investigating how preoperative proteinuria is associated with surgical outcomes, including postoperative acute kidney injury (AKI) and readmission.

Objective

To assess preoperative urine protein levels as a biomarker for adverse surgical outcomes.

Design, Setting, and Participants

A retrospective, population-based study was conducted in a cohort of patients with and without known preoperative renal dysfunction undergoing elective inpatient surgery performed at 119 Veterans Affairs facilities from October 1, 2007, to September 30, 2014. Data analysis was conducted from April 4 to December 1, 2016. Preoperative dialysis, septic, cardiac, ophthalmology, transplantation, and urologic cases were excluded.

Exposures

Preoperative proteinuria as assessed by urinalysis using the closest value within 6 months of surgery: negative (0 mg/dL), trace (15-29 mg/dL), 1+ (30-100 mg/dL), 2+ (101-300 mg/dL), 3+ (301-1000 mg/dL), and 4+ (>1000 mg/dL).

Main Outcomes and Measures

Primary outcome was postoperative predischarge AKI and 30-day postdischarge unplanned readmission. Secondary outcomes included any 30-day postoperative outcome.

Results

Of 346 676 surgeries, 153 767 met inclusion criteria, with the majority including orthopedic (37%), general (29%), and vascular procedures (14%). Evidence of proteinuria was shown in 43.8% of the population (trace: 20.6%, 1+: 16.0%, 2+: 5.5%, 3+: 1.6%) with 20.4%, 14.9%, 4.3%, and 0.9%, respectively, of the patients having a normal preoperative estimated glomerular filtration rate (eGFR). In unadjusted analysis, preoperative proteinuria was significantly associated with postoperative AKI (negative: 8.6%, trace: 12%, 1+: 14.5%, 2+: 21.2%, 3+: 27.6%; P < .001) and readmission (9.3%, 11.3%, 13.3%, 15.8%, 17.5%, respectively, P < .001). After adjustment, preoperative proteinuria was associated with postoperative AKI in a dose-dependent relationship (trace: odds ratio [OR], 1.2; 95% CI, 1.1-1.3, to 3+: OR, 2.0; 95% CI, 1.8-2.2) and 30-day unplanned readmission (trace: OR, 1.0; 95% CI, 1.0-1.1, to 3+: OR, 1.3; 95% CI, 1.1-1.4). Preoperative proteinuria was associated with AKI independent of eGFR.

Conclusions and Relevance

Proteinuria was associated with postoperative AKI and 30-day unplanned readmission independent of preoperative eGFR. Simple urine assessment for proteinuria may identify patients at higher risk of AKI and readmission to guide perioperative management.

Trace proteinuria by dipstick screening is associated with metabolic syndrome, hypertension, and diabetes

BACKGROUND

The purpose of this study is to determine the association of dipstick-determined trace proteinuria with metabolic syndrome (MetS) and its components in each age, gender, and eGFR category among a large general population.

METHODS

A total of 270,190 people (102,223 men and 167,967 women) aged 40-74 years were included. Subjects were categorized as having negative, trace, and positive proteinuria by the dipstick method.

RESULTS

The prevalence of MetS increased with increasing levels of proteinuria in any estimated glomerular filtration rate (eGFR) category (odds ratios for MetS relative to negative proteinuria: 1.22, 1.23, and 1.25 for trace proteinuria, and 2.19, 1.81, and 1.80 for positive proteinuria among subjects with eGFR of ≥ 90, 60-89, and 45-59 ml/min/1.73 m², respectively). These associations were statistically significant in each age and sex category. Among MetS components, the prevalence of hypertension and diabetes increased with increasing levels of proteinuria (odds ratios for hypertension: 1.23 and 1.87, and odds ratios for diabetes: 1.28 and 2.18 for trace and positive proteinuria, respectively), which were similarly observed in any eGFR category. There were little or no differences in the prevalence of abdominal obesity and dyslipidemia (reduced HDL-cholesterol and/or elevated triglycerides) between the levels of proteinuria.

CONCLUSION

Subjects with dipstick-determined trace proteinuria showed intermediate risk of having MetS, hypertension, and diabetes between negative and positive proteinuria in any eGFR category in a large general population. Thus, MetS components should be checked for subjects with trace proteinuria even in those with normal eGFR for the early prevention of cardiovascular diseases.

Traffic-related air pollution associated with chronic kidney disease among elderly residents in Taipei City

The associations of air pollution with chronic kidney disease (CKD) have not yet been fully studied. We enrolled 8,497 Taipei City residents older than 65 years and calculated the estimated glomerular filtration rate (eGFR) using the Taiwanese Chronic Kidney Disease Epidemiology Collaboration equation. Proteinuria was assessed via dipstick on voided urine. CKD prevalence and risk of progression were defined according to the KDIGO 2012 guidelines. Land-use regression models were used to estimate the participants' one-year exposures to PM of different sizes and traffic-related exhaust, PM_2.5 absorbance, nitrogen dioxide (NO₂), and NO_x. Generalized linear regressions and logistic regressions were used to examine the associations of one-year air pollution exposures with eGFR, proteinuria, CKD prevalence and risk of progression. The results showed that the interquartile range (IQR) increments of PM_2.5 absorbance (0.4 × 10^-5/m) and NO₂ (7.0 μg/m³) were associated with a 1.07% [95% confidence interval (CI): 0.54-1.57] and 0.84% (95% CI: 0.37-1.32) lower eGFR, respectively; such relationships were magnified in subjects who had an eGFR >60 ml/min/1.73 m² or who were non-diabetic. Similar associations were also observed for PM₁₀ and PM_2.5-10. Two-pollutant models showed that PM₁₀ and PM_2.5 absorbance were associated with a lower eGFR. The odd ratios (ORs) of CKD prevalence and risk of progression also increased with exposures to PM_2.5 absorbance and NO_2. In summary, one-year exposures to traffic-related air pollution were associated with lower eGFR, higher CKD prevalence, and increased risk of CKD progression among the elderly population. Air pollution-related impaired renal function was stronger in non-CKD and non-diabetic subjects.

High and low sodium intakes are associated with incident chronic kidney disease in patients with normal renal function and hypertension

The association between salt intake and renal outcome in subjects with preserved kidney function remains unclear. Here we evaluated the effect of sodium intake on the development of chronic kidney disease (CKD) in a prospective cohort of people with normal renal function. Data were obtained from the Korean Genome and Epidemiology Study, a prospective community-based cohort study while sodium intake was estimated by a 24-hour dietary recall Food Frequency Questionnaire. A total of 3,106 individuals with and 4,871 patients without hypertension were analyzed with a primary end point of CKD development [a composite of estimated glomerular filtration rate (eGFR) under 60 mL/min/1.73 m² and/or development of proteinuria during follow-up]. The median ages were 55 and 47 years, the proportions of males 50.9% and 46.3%, and the median eGFR 92 and 96 mL/min/1.73 m² in individuals with and without hypertension, respectively. During a median follow-up of 123 months in individuals with hypertension and 140 months in those without hypertension, CKD developed in 27.8% and 16.5%, respectively. After adjusting for confounders, multiple Cox models indicated that the risk of CKD development was significantly higher in people with hypertension who consumed less than 2.08 g/day or over 4.03 g/day sodium than in those who consumed between 2.93-4.03 g/day sodium. However, there was no significant difference in the incident CKD risk among each quartile of people without hypertension. Thus, both high and low sodium intakes were associated with increased risk for CKD, but this relationship was only observed in people with hypertension.

Association between Sarcopenia and Dipstick Proteinuria in the Elderly Population: The Korea National Health and Nutrition Examination Surveys 2009-2011

Background

Sarcopenia and proteinuria are significant health difficulties in the elderly; however, few studies have investigated their relationship. In this study, we investigated the association between sarcopenia and proteinuria in Korean subjects over 60 years old.

Methods

We included data from the Korean National Health and Nutrition Examination Survey, a cross-sectional, nationally representative survey conducted from 2009 to 2011 (n=4,008). Sarcopenia was defined using appendicular skeletal muscle mass as a percentage of body weight. Proteinuria was defined by a urine dipstick test result above trace levels.

Results

The overall proteinuria prevalence was 7.2%. The incidence of sarcopenia was significantly higher in subjects with proteinuria. The prevalence of proteinuria was significantly higher in the sarcopenic group (5.5% vs. 14.5% in the non-chronic kidney disease (CKD) group; 17.2% vs. 23.2% in the CKD group) than in the non-sarcopenic group. Furthermore, sarcopenic participants had worse metabolic parameters, such as higher body mass indexes, waist circumferences, and fasting glucose levels, and lower high-density lipoprotein cholesterol levels than those in the non-CKD group. After adjustment for confounders, the odds ratios (95% confidence interval) for proteinuria were 2.84 (1.92–4.18) in the sarcopenic non-CKD group, 3.70 (2.59–5.30) in the non-sarcopenic CKD group, and 5.19 (2.64–10.18) in the sarcopenic CKD group, compared to the non-sarcopenic, non-CKD group. Sarcopenia increased the proteinuria risk in elderly participants without CKD, even after adjustment for obesity, hypertension, diabetes, and metabolic syndrome.

Conclusion

These findings showed that sarcopenia was associated with dipstick proteinuria, especially in elderly participants without CKD, regardless of comorbidities.

Proteinuria Detected by Urine Dipstick Test as a Risk Factor for Atrial Fibrillation: A Nationwide Population-Based Study

Proteinuria is one of the well-known risk factors for cardiovascular disease. However the impact of proteinuria on the incidence of atrial fibrillation (AF) is unclear. In this study, we investigated the association between proteinuria detected using urine dipstick test and the risk of AF. A total of 18,201,275 individuals were analyzed, who had no prior AF and had received biennial health checkups provided by the National Health Insurance Service between 2005 and 2008 in Korea. Incidences of AF were ascertained through the end of 2015. During a mean follow-up of 9.6 years, a total of 324,764 (1.8%) developed AF (1.86 per 1,000 person-years). In Cox regression models, proteinuria was associated with an increased risk of AF: adjusted HR and 95% CI of AF occurrence were 1.13 (1.10-1.16), 1.34 (1.31-1.38), 1.53 (1.48-1.58), 1.82 (1.71-1.94), and 1.86 (1.61-2.16) in individuals with trace, 1+, 2+, 3+, and 4+ proteinuria, respectively, compared with those without proteinuria. The result was consistent even after additional adjustment for estimated glomerular filtration rate. In addition, the risk of AF further increased or decreased according to the follow-up dipstick test results. Thus, proteinuria measured with a dipstick test might be considered a potent risk factor for AF development.

High dietary phosphorus density is a risk factor for incident chronic kidney disease development in diabetic subjects: a community-based prospective cohort study

Background: High serum phosphorus concentrations are associated with an increased risk of cardiovascular disease and progression of chronic kidney disease (CKD). However, the relation between dietary phosphorus intake and CKD development has not been well evaluated.Objective: In this study, we investigated the impact of dietary phosphorus density on the development of incident CKD in a cohort of subjects with normal renal function.Design: Data were retrieved from the Korean Genome and Epidemiology Study, a prospective community-based cohort study. The study cohort consisted of subjects aged 40-69 y, who were followed up biennially from 2001 to 2014. A total of 873 subjects with diabetes mellitus (DM) and 5846 subjects without DM (non-DM) were included in the final analysis. The primary endpoint was incident CKD, defined as a composite of estimated glomerular filtration rate <60 mL · min^-1 · 1.73 m^-2 and/or the development of proteinuria.Results: In the DM and non-DM groups, the mean ages of the participants were 55.6 ± 8.7 and 51.4 ± 8.6 y, the numbers of male subjects were 454 (52.0%) and 2784 (47.6%), and the mean estimated glomerular filtration rates were 91.6 ± 14.0 and 94.5 ± 14.0 mL · min^-1 · 1.73 m^-2, respectively. The mean values of dietary phosphorus density, defined as the ratio of a single-day dietary phosphorus amount to the total daily calorie intake, were 0.51 ± 0.08 mg/kcal in the DM group and 0.51 ± 0.07 mg/kcal in the non-DM group. During the follow-up, CKD newly developed in 283 (32.4%) and 792 subjects (13.5%) in the DM and non-DM groups, respectively. When the subjects were divided into quartiles according to the dietary phosphorus density in each group, the highest quartile was significantly associated with the development of incident CKD by multiple Cox proportional hazard analysis in the DM group (P = 0.02) but not in the non-DM group (P = 0.72).Conclusions: High dietary phosphorus density is associated with an increased risk of CKD development in DM patients with normal renal function. The causality in this association needs to be tested in a randomized controlled trial.

Prevalence of Proteinuria and Other Abnormalities in Urinalysis Performed in the Urology Clinic

OBJECTIVE

To compare the prevalence of proteinuria in the urology clinic with other outpatient settings. Chronic kidney disease is classified according to cause, glomerular filtration rate, and proteinuria. Proteinuria may be more prevalent in patients with known chronic kidney disease, renal disorders (benign or malignant), or after urologic surgery.

METHODS

A cross-sectional study of 3 populations undergoing urinalysis (UA) testing was carried out: general outpatients (n = 20,334), urology outpatients (n = 5023), and kidney cancer patients (n = 1016). Proteinuria was classified under Kidney Disease: Improving Global Outcomes guidelines: A1 (<30 mg), A2 (30-300 mg), and A3 (>300 mg).

RESULTS

Proteinuria was detected throughout a community-based health system in 8.6% of UA (8.2%: A2; 0.4%: A3). In comparison, 18.6% of urology office-performed UA had proteinuria (16.0%: A2, 2.5%: A3) (P < .0001 vs non-urology). Kidney cancer patients were more likely to have proteinuria (17.9%: A2, 3.8%: A3). The proportion with A3 was significantly higher in urology and kidney cancer patients when compared with other outpatients (each P < .0001), and in the kidney cancer subgroup compared with all urology patients (P < .0001). Additional abnormalities were frequently present on microscopic analysis of UA in the urology clinic, including hematuria (20.9%), pyuria (21.8%), and bacteriuria (3.1%).

CONCLUSION

The value of UA in the urology clinic as a screening test for proteinuria and other conditions appears high, with >56% having at least 1 abnormality. The population risk of proteinuria in the urology clinic is 18.5%, which is higher than that observed in non-urology clinics. Patients with kidney cancer appear more likely to have proteinuria than the average urology patient. We recommend evaluation of urology patients with UA to identify proteinuria.

Low Rice Intake Is Associated with Proteinuria in Participants of Korea National Health and Nutrition Examination Survey

Little is known about the risk factors of proteinuria in the Asian population. On the basis of the association between rice intake patterns and chronic diseases, we hypothesized that rice intake patterns are associated with proteinuria in the Asian population. Data, including data regarding rice intake frequency and dipstick urinalysis results, from the Korea National Health and Nutrition Examination Survey in 1998, 2001, 2005, and 2007 were analyzed. The study involved 19,824 participants who were older than 20 years of age. Low rice intake was defined as consumption of rice ≤ 1 time/day. Proteinuria was defined as dipstick urinalysis protein ≥ 1 positive. Among the 19,824 participants, the prevalence of low rice intake and proteinuria were 17.3% and 2.9%, respectively. The low rice intake group showed a higher rate of proteinuria than the non-low rice intake group did (3.8% vs. 2.7%, P < 0.001). In multivariate logistic regression analysis, the odds ratio (OR) of low rice intake for proteinuria was 1.54 (95% confidence interval (CI): 1.25-1.89; P < 0.001). Low rice intake was also independently associated with high blood pressure (OR: 1.43, 95% CI: 1.31-1.56; P < 0.001) and diabetes (OR: 1.43, 95% CI: 1.27-1.62; P < 0.001). In conclusion, low rice intake was found to be independently associated with proteinuria in the Asian population, which might have been affected by the associations of low rice intake with high blood pressure and diabetes. Future prospective studies are needed to confirm the results of this study.

Emergence of Dipstick Proteinuria Predicts Overt Nephropathy in Patients Following Stem Cell Transplantation

BACKGROUND

Stem cell transplantation (SCT) places a heavy burden on the kidneys, often resulting in renal dysfunction or nephrotic syndrome. This study attempted to show that early-onset proteinuria predicts the development of overt nephropathy.

METHODS

A total of 831 patients who received allogeneic SCT were surveyed. Excluding those with prior kidney disease and those lacking in an observation period ≥1 year after SCT, 251 patients were eligible for the study. Dipstick proteinuria ≥1+ within 1 year after SCT was defined as 'incident proteinuria', and subsequent persistence of an estimated glomerular filtration rate of <60 ml/min/1.73 m2 at 1 year or longer after SCT was defined as 'incident chronic kidney disease (CKD)'. Between-group differences were analyzed using the chi-square or Mann-Whitney U test. Factors associated with the incidence of CKD were investigated by multivariate Cox proportional regression analysis. Kidney-biopsied tissue was examined in all nephrotic syndrome patients.

RESULTS

The mean duration of follow-up was 4 years. Thirty-four (13.5%) and 66 (26.3%) patients developed incident proteinuria and incident CKD, respectively. Nine (3.6%) patients developed nephrotic syndrome mainly due to membranous nephropathy. The incidence of CKD was significantly greater in patients with incident proteinuria than those without (61.8 vs. 20.7%, p < 0.0001), and incident dipstick proteinuria was a significant risk for incident CKD (hazard ratio 4.39, 95% CI 2.44-7.73, p < 0.0001).

CONCLUSION

SCT patients who manifest dipstick proteinuria are predisposed to overt nephropathy. Routine monitoring of the urine dipstick test is strongly recommended, as it facilitates early nephrology care for post-SCT patients.

Neck circumference predicts renal function decline in overweight women: A community-based prospective cohort study

Chronic kidney disease (CKD) is characterized by increased risks of morbidity and mortality. Upper-body subcutaneous fat, which is commonly estimated from the neck circumference (NC), was revealed to be the main reservoir of circulating nonesterified fatty acids in overweight patients. Despite a close association between NC and metabolic complications, the relationship of NC with renal function has not been fully investigated. In this study, the impact of NC on the development of incident CKD was elucidated.The data were retrieved from the Korean Genome and Epidemiology Study cohort. The subjects were followed at 2-year intervals from 2003 to 2011. Overweight was defined as a body mass index of ≥23 kg/m. A total of 4298 cohort subjects were screened. After exclusion, 2268 overweight subjects were included for the final analysis. The primary end point was incident CKD, which was defined as a composite of estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m or the development of proteinuria.The mean patient age was 36.3 ± 3.0 years, and 1285 (56.7%) were men. They were divided into 2 groups according to the median NC in male and female subjects, separately. In both sexes, hypertension (men, P < 0.001; women, P = 0.009) and diabetes (men, P = 0.002; women, P < 0.001) were significantly more prevalent in the big NC group than in the small NC group. In contrast, eGFR was significantly lower only in male subjects of the big NC group (P < 0.001), whereas it was comparable between the small and big NC groups (P = 0.167). In multivariate Cox proportional hazards regression analysis, NC values were independently associated with incident CKD development in female subjects after adjusting for multiple confounding factors (per 1 cm increase, hazard ratio [95% confidence interval] = 1.159 [1.024-1.310], P = 0.019) but not in male subjects.NC is independently associated with the development of CKD in overweight female subjects, suggesting that it could be a practical risk factor for CKD.