urinary biomarkers in relapsing antineutrophil cytoplasmic antibody-associated vasculitis

Urinary Kim-1 Correlates with Interstitial Nephritis Activity in Patients with Microscopic Polyangiitis

BACKGROUND

Microscopic polyangiitis (MPA) is a type of necrotizing vasculitis that primarily affects small vessels and belongs to the spectrum of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs). While previous studies have identified potential prognostic biomarkers, further research is needed to validate a reliable marker for risk stratification in clinical practice. Kidney injury molecule-1 (Kim-1), a transmembrane protein expressed on proximal tubular epithelial cells, has been implicated in tubular damage. This study investigated the potential of Kim-1 as a biomarker in MPA.

METHODS

Kidney biopsy tissues, along with urine and blood samples, were retrospectively analyzed from 52 MPA patients and compared to urine samples from 7 healthy controls. Global disease activity was assessed using the Birmingham vasculitis activity score (BVAS) and vasculitis damage index, while renal disease activity was evaluated using renal BVAS (BVAS-R).

RESULTS

Urinary Kim-1 levels were significantly elevated in MPA patients compared to healthy controls. Urinary Kim-1 was positively correlated with the Mayo Clinic Chronicity Score (MCCS) but not with the ANCA Kidney Risk Score (AKRiS), whereas tubular Kim-1 was associated with AKRiS but not with MCCS, indicating their distinct pathological significance. Higher tubular Kim-1 expression was observed in patients with elevated BVAS-R. Urinary Kim-1 levels correlated with proteinuria and were associated with the Mayo Clinic Chronicity Score (MCCS) and ANCA Kidney Risk Score (AKRiS) but not with glomerular lesion severity. Unlike C-reactive protein (CRP), neither urinary nor tubular Kim-1 predicted MPA recurrence.

CONCLUSIONS

Urinary Kim-1 reflects histopathologic findings and renal impairment but does not predict systemic disease activity or recurrence in MPA, demonstrating its potential clinical utility as a biomarker for assessing chronic renal damage.

SERPINA3, FGA, AGP1, ITIH3 and SAA1 as novel biomarkers for eosinophilic granulomatosis with polyangiitis diagnosis and activity assessment

OBJECTIVE

The objective of this study was to identify novel biomarkers for diagnosis and prediction of active eosinophilic granulomatosis with polyangiitis (EGPA) through data-independent acquisition (DIA) analysis.

METHODS

Plasma samples from 11 EGPA patients and 10 healthy controls (HCs) were analysed through DIA to identify potential biomarkers. The results were validated in 32 EGPA patients, 24 disease controls (DCs), and 20 HCs using ELISA. The receiver operating characteristic (ROC) curve was used to assess the diagnostic value of candidate biomarkers.

RESULTS

Thirty-five differentially expressed proteins (DEPs) (24 upregulated and 11 downregulated) were screened between the EGPA and HC groups. Five proteins, including serine proteinase inhibitor A3 (SERPINA3), alpha-fibrinogen (FGA), alpha-1 acid glycoprotein 1(AGP1), inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3), and serum amyloid A1 (SAA1), were significantly upregulated in EGPA compared with HCs. Apart from SAA1, all proteins were also higher in EGPA patients compared with DCs. Furthermore, a panel of SERPINA3 and SAA1 exhibited potential diagnostic value for EGPA, with an area under the curve (AUC) of 0.953, while a panel of SERPINA3, FGA, AGP1 and ITIH3 showed good discriminative power for differentiating EGPA from DCs, with an AUC of 0.926. Moreover, SERPINA3, FGA and AGP levels were significantly higher in active EGPA and correlated well with disease activity. A combination of SERPINA3 and AGP1 exhibited an excellent AUC of 0.918 for disease activity assessment.

CONCLUSION

SERPINA3, FGA, AGP1, ITIH3 and SAA1 were identified as potential biomarkers for EGPA diagnosis and disease activity assessment. Among them, as a single biomarker, SERPINA3 had the best diagnostic performance.

ANCA-Associated Glomerulonephritis: Diagnosis and Therapy Proceedings of the Henry Shavelle Lectureship

Background

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) frequently affects the kidney. Glomerulonephritis (GN) in AAV, ANCA-GN, not only dictates therapeutic decisions but is also of relevance for overall survival influencing the risk of cardiovascular disease and serious infections.

Summary

A diagnosis of ANCA-GN includes laboratory investigations including urinalysis and a thorough assessment of potential organ involvement. A kidney biopsy can be performed to ascertain the diagnosis but has an additional prognostic relevance and tools have been established to predict long-term kidney survival. Experimental biomarkers indicating kidney inflammation include urinary soluble CD163 and the presence of urinary T cells. Therapeutic options are refined and some of these therapies, such as the added value of performing plasma exchange, are the matter of controversial discussions. Safe reduction of cumulative exposure to glucocorticoids and eventually the use of avacopan to substantially reduce glucocorticoid exposure has been implemented in most centers. In the remission of maintenance, the optimal duration of therapy is still unclear, but extended use of rituximab as maintenance agent has shown long-term remission rates, thus limiting the damage accrued by relapsing disease and thus also reducing the risk of end-stage kidney disease (ESKD). Avacopan has been the first agent with a glomerular filtration rate-sparing effect, likely due to more rapid control of kidney inflammation. Those reaching ESKD should be evaluated for kidney transplantation and the risk of remaining on dialysis must be balanced against the risk of recurrence of disease following transplantation.

Key Messages

The advent of a magnitude of landmark studies in ANCA-GN has refined diagnostic approaches, implemented tools to predict kidney outcome, and eventually led to the approval of newer therapies with avacopan, the latest addition to the armamentarium. Once ESKD is present, patients should be considered for kidney transplantation as remaining on dialysis portends poor overall prognosis.

New Biomarkers for Systemic Necrotizing Vasculitides

Systemic necrotising vasculitides (SNVs) pose significant challenges due to their diverse clinical manifestations and variable outcomes. Therefore, identifying reliable biomarkers holds promise for improving precision medicine in SNVs. This review explores emerging biomarkers aiming to enhance diagnostic accuracy, prognostic assessment, and disease monitoring. We discuss recent advances in immunological biomarkers, inflammatory indicators, and other parameters that exhibit potential diagnostic and prognostic utility. A comprehensive understanding of these biomarkers may facilitate earlier and more accurate SNV detection, aiding in timely intervention and personalized treatment strategies. Furthermore, we highlight the evolving landscape of disease monitoring through innovative biomarkers, shedding light on their dynamic roles in reflecting disease activity and treatment response. Integrating these novel biomarkers into clinical practice can revolutionize the management of SNVs, ultimately improving patient outcomes and quality of life.

Non-Invasive Biomarkers for Diagnosis, Risk Prediction, and Therapy Guidance of Glomerular Kidney Diseases: A Comprehensive Review

Effective management of glomerular kidney disease, one of the main categories of chronic kidney disease (CKD), requires accurate diagnosis, prognosis of progression, assessment of therapeutic efficacy, and, ideally, prediction of drug response. Multiple biomarkers and algorithms for the assessment of specific aspects of glomerular diseases have been reported in the literature. Though, the vast majority of these have not been implemented in clinical practice or are not available on a global scale due to limited access, missing medical infrastructure, or economical as well as political reasons. The aim of this review is to compile all currently available information on the diagnostic, prognostic, and predictive biomarkers currently available for the management of glomerular diseases, and provide guidance on the application of these biomarkers. As a result of the compiled evidence for the different biomarkers available, we present a decision tree for a non-invasive, biomarker-guided diagnostic path. The data currently available demonstrate that for the large majority of patients with glomerular diseases, valid biomarkers are available. However, despite the obvious disadvantages of kidney biopsy, being invasive and not applicable for monitoring, especially in the context of rare CKD etiologies, kidney biopsy still cannot be replaced by non-invasive strategies.

Serum Complement C4 Levels Are a Useful Biomarker for Predicting End-Stage Renal Disease in Microscopic Polyangiitis

This study aimed to evaluate the risk factors for end-stage renal disease (ESRD) in microscopic polyangiitis (MPA). In total, 74 patients with MPA were enrolled, and we compared the baseline clinical characteristics and disease activity between MPA patients who have progressed to ESRD and those without ESRD to select predictive factors for ESRD. Out of 74 patients, 12 patients (16.2%) had ESRD during follow-up. Serum C4 levels were significantly higher in MPA patients who have progressed to ESRD than in those without ESRD (p = 0.009). Multivariate analyses revealed that high serum creatinine levels (odds ratio (OR) 4.4, 95% confidence interval (CI) 1.25-15.5) and high serum C4 levels (OR 1.24, 95% CI 1.03-1.49) were risk factors for ESRD. Using receiver operating characteristic analysis, the cut-off value for initial serum C4 levels and serum creatinine levels were 29.6 mg/dL and 3.54 mg/dL, respectively. Patients with MPA with a greater number of risk factors (serum C4 levels > 29.6 mg/dL and serum creatinine levels > 3.54 mg/dL) had a higher ESRD progression rate. Serum C4 levels were significantly positively correlated with serum creatinine levels and kidney Birmingham vasculitis activity score (p = 0.02 and 0.04, respectively). These results suggest that serum C4 levels are useful tools for assessing renal disease activity and prognosis in MPA.

Kidney injury molecule 1 (KIM-1): a potential biomarker of acute kidney injury and tubulointerstitial injury in patients with ANCA-glomerulonephritis

Background

Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein expressed by proximal tubular cells, recognized as an early, sensitive and specific urinary biomarker for kidney injury. Blood KIM-1 was recently associated with the severity of acute and chronic kidney damage but its value in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis with glomerulonephritis (ANCA-GN) has not been studied. Thus, we analyzed its expression at ANCA-GN diagnosis and its relationship with clinical presentation, kidney histopathology and early outcomes.

Methods

We assessed KIM-1 levels and other pro-inflammatory molecules (C-reactive protein, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1 and pentraxin 3) at ANCA-GN diagnosis and after 6 months in patients included in the Maine-Anjou registry, which gathers data patients from four French Nephrology Centers diagnosed since January 2000.

Results

Blood KIM-1 levels were assessed in 54 patients. Levels were elevated at diagnosis and decreased after induction remission therapy. KIM-1 was associated with the severity of renal injury at diagnosis and the need for kidney replacement therapy. In opposition to other pro-inflammatory molecules, KIM-1 correlated with the amount of acute tubular necrosis and interstitial fibrosis/tubular atrophy (IF/TA) on kidney biopsy, but not with interstitial infiltrate or with glomerular involvement. In multivariable analysis, elevated KIM-1 predicted initial estimated glomerular filtration rate (β = -19, 95% CI -31, -7.6, P = .002).

Conclusion

KIM-1 appears as a potential biomarker for acute kidney injury and for tubulointerstitial injury in ANCA-GN. Whether KIM-1 is only a surrogate marker or is a key immune player in ANCA-GN pathogenesis remain to be determined.

Old known and possible new biomarkers of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of multisystem disorders involving severe, systemic, small-vessel vasculitis with short- and long term serious and life-threating complications. Despite the simplification of treatment, fundamental aspects concerning assessment of its efficacy and its adaptation to encountered complications or to the relapsing/remitting/subclinical disease course remain still unknown. The pathogenesis of AAV is complex and unique, and despite the progress achieved in the last years, much has not to be learnt. Foremost, there is still no accurate marker enabling us to monitoring disease and guide therapy. Therefore, the disease management relays often on clinical judgment and follows a" trial and error approach". In the recent years, an increasing number of new molecules s have been explored and used for this purpose including genomics, B- and T-cell subpopulations, complement system factors, cytokines, metabolomics, biospectroscopy and components of our microbiome. The aim of this review is to discuss both the role of known historical and clinically established biomarkers of AAV, as well as to highlight potential new ones, which could be used for timely diagnosis and monitoring of this devastating disease, with the goal to improve the effectiveness and ameliorate the complications of its demanding therapy.

The Potential Applications of Raman Spectroscopy in Kidney Diseases

Raman spectroscopy (RS) is a spectroscopic technique based on the inelastic interaction of incident electromagnetic radiation (from a laser beam) with a polarizable molecule, which, when scattered, carries information from molecular vibrational energy (the Raman effect). RS detects biochemical changes in biological samples at the molecular level, making it an effective analytical technique for disease diagnosis and prognosis. It outperforms conventional sample preservation techniques by requiring no chemical reagents, reducing analysis time even at low concentrations, and working in the presence of interfering agents or solvents. Because routinely utilized biomarkers for kidney disease have limitations, there is considerable interest in the potential use of RS. RS may identify and quantify urinary and blood biochemical components, with results comparable to reference methods in nephrology.

Automated Computational Detection of Disease Activity in ANCA-Associated Glomerulonephritis Using Raman Spectroscopy: A Pilot Study

Biospectroscopy offers the ability to simultaneously identify key biochemical changes in tissue associated with a given pathological state to facilitate biomarker extraction and automated detection of key lesions. Herein, we evaluated the application of machine learning in conjunction with Raman spectroscopy as an innovative low-cost technique for the automated computational detection of disease activity in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated glomerulonephritis (AAGN). Consecutive patients with active AAGN and those in disease remission were recruited from a single UK centre. In those with active disease, renal biopsy samples were collected together with a paired urine sample. Urine samples were collected immediately prior to biopsy. Amongst those in remission at the time of recruitment, archived renal tissue samples representative of biopsies taken during an active disease period were obtained. In total, twenty-eight tissue samples were included in the analysis. Following supervised classification according to recorded histological data, spectral data from unstained tissue samples were able to discriminate disease activity with a high degree of accuracy on blind predictive modelling: F-score 95% for >25% interstitial fibrosis and tubular atrophy (sensitivity 100%, specificity 90%, area under ROC 0.98), 100% for necrotising glomerular lesions (sensitivity 100%, specificity 100%, area under ROC 1) and 100% for interstitial infiltrate (sensitivity 100%, specificity 100%, area under ROC 0.97). Corresponding spectrochemical changes in paired urine samples were limited. Future larger study is required, inclusive of assigned variables according to novel non-invasive biomarkers as well as the application of forward feature extraction algorithms to predict clinical outcomes based on spectral features.

Serum Biomarkers of Disease Activity in Longitudinal Assessment of Patients with ANCA-Associated Vasculitis

OBJECTIVE

Improved biomarkers of current disease activity and prediction of relapse are needed in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). For clinical relevance, biomarkers must perform well longitudinally in patients on treatment and in patients with nonsevere flares.

METHODS

Twenty-two proteins were measured in 347 serum samples from 74 patients with AAV enrolled in a clinical trial. Samples were collected at Month 6 after remission induction, then every 3 months until Month 18, or at the time of flare. Associations of protein concentrations with concurrent disease activity and with future flare were analyzed using mixed-effects models, Cox proportional hazards models, and conditional logistic regression.

RESULTS

Forty-two patients had flares during the 12-month follow-up period, and 32 remained in remission. Twenty-two patients had severe flares. Six experimental markers (CXCL13, IL-6, IL-8, IL-15, IL-18BP, and matrix metalloproteinase-3 [MMP-3]) and ESR were associated with disease activity using all three methods (P < 0.05, with P < 0.01 in at least one method). A rise in IL-8, IL-15, or IL-18BP was associated temporally with flare. Combining C-reactive protein (CRP), IL-18BP, neutrophil gelatinase-associated lipocalin (NGAL), and sIL-2Rα improved association with active AAV. CXCL13 and MMP-3 were increased during treatment with prednisone, independent of disease activity. Marker concentrations during remission were not predictive of future flare.

CONCLUSION

Serum biomarkers of inflammation and tissue damage and repair have been previously shown to be strongly associated with severe active AAV were less strongly associated with active AAV in a longitudinal study that included mild flares and varying treatment. Markers rising contemporaneously with flare or with an improved association in combination merit further study.

ANCA status and renal parameters at month 12 post-diagnosis can help predict subsequent relapses in patients with granulomatosis with polyangiitis

OBJECTIVE

To determine the predictive value of disease characteristics at 12-month follow-up after the diagnosis of GPA for subsequent relapses in a cohort of patients followed at a tertiary vasculitis clinic.

METHODS

Demographic, clinical, and biological data at diagnosis and during follow-up from patients with GPA followed for at least 24 months at the Mount Sinai Hospital Vasculitis Clinic in Toronto, Canada were extracted from the Canadian Vasculitis Research Network (CanVasc) database and analyzed. The association between ANCA status and type (PR3- or MPO-ANCA), presence of microscopic hematuria, or serum creatinine level at follow-up month 12 ± 3 (M12) and relapses after M12 were assessed using Cox proportional hazard models.

RESULTS

A total of 113 GPA patients were included in this study (50 ANCA positive, 63 ANCA negative at M12). Patient demographics and disease characteristics were similar at diagnosis, including the treatments used for induction and at M12. The global 5-year relapse rate was 55.8%, without any difference in the relapse rates after M12 between those ANCA-positive or negative at M12. However, in multivariate analyses, MPO-ANCA positivity at M12 was predictive of increased relapses after M12 (hazard ratio [HR] 3.54, P=0.01), as was the presence of microhematuria at M12 (HR 1.91, P=0.04). In contrast, higher serum creatinine levels at M12 were associated with a decreased risk of subsequent relapse (HR 0.99, P=0.04).

CONCLUSION

In this cohort of patients with GPA, MPO-ANCA positivity and persistent microscopic hematuria at M12 were associated with increased risk of subsequent relapse, and could thus have value to predict disease outcome during follow-up.

Distinguishing active from quiescent disease in ANCA-associated vasculitis using attenuated total reflection Fourier-transform infrared spectroscopy

The current lack of a reliable biomarker of disease activity in anti-neutrophil cytoplasmic autoantibody (ANCA) associated vasculitis poses a significant clinical unmet need when determining relapsing or persisting disease. In this study, we demonstrate for the first time that attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy offers a novel and functional candidate biomarker, distinguishing active from quiescent disease with a high degree of accuracy. Paired blood and urine samples were collected within a single UK centre from patients with active disease, disease remission, disease controls and healthy controls. Three key biofluids were evaluated; plasma, serum and urine, with subsequent chemometric analysis and blind predictive model validation. Spectrochemical interrogation proved plasma to be the most conducive biofluid, with excellent separation between the two categories on PC2 direction (AUC 0.901) and 100% sensitivity (F-score 92.3%) for disease remission and 85.7% specificity (F-score 92.3%) for active disease on blind predictive modelling. This was independent of organ system involvement and current ANCA status, with similar findings observed on comparative analysis following successful remission-induction therapy (AUC > 0.9, 100% sensitivity for disease remission, F-score 75%). This promising technique is clinically translatable and warrants future larger study with longitudinal data, potentially aiding earlier intervention and individualisation of treatment.

Biomarkers in ANCA-Associated Vasculitis: Potential Pitfalls and Future Prospects

Over the past 3 decades, significant advancements in the understanding of the pathophysiology of ANCA-associated vasculitis has led to the development of a multitude of potential candidate biomarkers. Accompanied by the advent of increasingly effective therapeutic strategies, the need for a dependable biomarker to help determine the extent of disease activity and risk of relapse is ever present. Implementation of such a biomarker would enable tailored therapy, optimizing disease control while helping to mitigate unnecessary exposure to therapy and potential treatment-related damage. Although far from perfect, ANCA serology and B-cell population are the two main staple biomarker tools widely used in practice to help supplement clinical assessment. Over recent years, the application and progress of more novel biomarker tools have arisen in both organ-limited and multisystem disease, including genomics, urinary proteins, degradation products of the alternative complement system, cytokines, metabolomics, and biospectroscopy. Validation studies and clinical translation of these tools are required, with serial assessment of disease activity and determination of therapy according to biomarker status correlated with patient outcomes.

Clinical Use of Complement, Inflammation, and Fibrosis Biomarkers in Autoimmune Glomerulonephritis

Introduction

Complement activation, inflammation, and fibrosis play central roles in the mechanisms of injury in autoimmune glomerulonephritis (GN) but they are seldom assessed in epidemiologic studies. The measurement of urinary biomarkers of these pathways of injury could parallel disease activity and add clinical value beyond proteinuria.

Methods

We performed a prospective cohort study of 100 patients with focal and segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), IgA nephropathy (IgAN), lupus nephritis (LN), anti-neutrophil cytoplasmic autoantibody-associated vasculitis (AAV), and membranoproliferative GN (MPGN) followed for 33 (18-54) months. Repeated urinary samples were collected throughout their follow-up to determine proteinuria, urinary sC5b-9, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta 1 (TGF-β1), expressed as creatinine ratios. We identified 177 periods of active and inactive disease based on current remission definitions for each disease.

Results

Urinary sC5b-9, MCP-1, and TGF-β1 were present in each disease. In periods leading to a remission, the reduction of urinary sC5b-9 was 91%, greater than for proteinuria with 76%. During inactive periods, those who did not experience a relapse maintained lower levels of biomarkers compared with those who relapsed. At that time, the increase in urinary sC5b-9 was significantly greater than the rise in proteinuria (8.5-fold increase compared with 3.2-fold) and urinary MCP-1 and TGF-β1. Using current remission definitions for each disease, thresholds for each biomarker were determined using receiver operating characteristic curves. Individuals who averaged levels below these cutoffs during their follow-up had better renal outcomes.

Conclusion

In autoimmune glomerular diseases, urinary sC5b-9, MCP-1, and TGF-β1 are present and parallel disease activity and outcomes. Urinary sC5b-9 appears to be a more discerning marker of immunologic remissions and relapses.

Hyperuricemia is associated with decreased renal function and occurrence of end-stage renal disease in patients with microscopic polyangiitis and granulomatosis with polyangiitis: a retrospective study

Current evidence suggests that high uric acid levels are associated with accelerated renal damage. However, the clinical impact of serum uric acid level on patients with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) is unknown. We aimed to evaluate the impact of hyperuricemia on such patients. A retrospective study was performed to obtain patients' demographic, clinical, and laboratory data from when they were diagnosed with MPA and GPA. Multivariable logistic regression and Cox hazard model analyses were performed to evaluate factors associated with hyperuricemia at diagnosis and predictive factors of end-stage renal disease (ESRD) development. Among 156 patients, 35 (22.4%) had hyperuricemia at baseline. Hyperuricemic patients had renal manifestation and impaired renal function more frequently than non-hyperuricemic patients. Logistic regression analysis revealed that serum creatinine was significantly associated with hyperuricemia at diagnosis [odds ratio 1.995; 95% confidence interval (CI), 1.503-2.648; P < 0.001]. Cox hazard model analysis revealed that body mass index and serum creatinine were significantly associated with ESRD when all variables were included, but hyperuricemia was independently associated with ESRD [hazard ratio (HR), 3.799; 95% CI 1.719-8.222; P < 0.001) when serum creatinine was excluded. Additionally, in a subgroup analysis of patients with decreased glomerular filtration rates (GFRs), serum uric acid was the sole predictor of ESRD (HR, 1.243; 95% CI 1.048-1.475; P = 0.013). Hyperuricemia is associated with renal damage and ESRD occurrence in MPA and GPA patients. Serum uric acid level is associated with ESRD occurrence in patients with decreased GFRs.

Management of ANCA associated vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is a small to medium vessel vasculitis associated with excess morbidity and mortality. This review explores how management of AAV has evolved over the past two decades with pivotal randomized controlled trials shaping the management of induction and maintenance of remission. Contemporary AAV care is characterized by approaches that minimize the cumulative exposure to cyclophosphamide and glucocorticoids, increasingly use rituximab for remission induction and maintenance, and consider therapies with less toxicity (for example, methotrexate, mycophenolate mofetil) for manifestations of AAV that do not threaten organ function or survival. Simultaneously, improvements in outcomes, such as renal and overall survival, have been observed. Additional trials and observational studies evaluating the comparative effectiveness of agents for AAV in various patient subgroups are needed. Prospective studies are necessary to assess the effect of psychosocial interventions on patient reported outcomes in AAV. Despite the expanding array of treatments for AAV, little guidance on how to personalize AAV care is available to physicians.

Urinary soluble CD163 and monocyte chemoattractant protein-1 in the identification of subtle renal flare in anti-neutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

Prior work has shown that urinary soluble CD163 (usCD163) displays excellent biomarker characteristics for detection of active renal vasculitis using samples that included new diagnoses with highly active renal disease. This study focused on the use of usCD163 in the detection of the more clinically relevant state of mild renal flare and compared results of usCD163 testing directly to testing of urinary monocyte chemoattractant protein-1 (uMCP-1).

METHODS

Patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV, n = 88) were identified within a serially sampled, longitudinal and multicentre cohort. Creatinine-normalized usCD163 and uMCP-1 levels were measured by enzyme-linked immunosorbent assay and, both alone and in combination, were compared between times of active renal AAV and during remission and/or active non-renal AAV.

RESULTS

Samples from 320 study visits included times of active renal vasculitis (n = 39), remission (n = 233) and active extrarenal vasculitis (n = 48). Median creatinine levels were 0.9 mg/dL [interquartile range (IQR) 0.8-1.2] in remission and 1.4 mg/dL (IQR 1.0-1.8) during renal flare. usCD163 levels were higher in patients with active renal vasculitis compared with patients in remission and those with active extrarenal vasculitis, with median values of 162 ng/mmol (IQR 79-337), 44 (17-104) and 38 (7-76), respectively (P < 0.001). uMCP-1 levels were also higher in patients with active renal vasculitis compared with patients in remission and those with active extrarenal vasculitis, with median values of 10.6 pg/mmol (IQR 4.6-23.5), 4.1 (2.5-8.4) and 4.1 (1.9-6.8), respectively (P < 0.001). The proposed diagnostic cut-points for usCD163 and uMCP-1 were 72.9 ng/mmol and 10.0 pg/mmol, respectively. usCD163 and uMCP-1 levels were marginally correlated (r2 = 0.11, P < 0.001). Combining novel and existing biomarkers using recursive tree partitioning indicated that elevated usCD163 plus either elevated uMCP-1 or new/worse proteinuria improved the positive likelihood ratio (PLR) of active renal vasculitis to 19.2.

CONCLUSION

A combination of usCD163 and uMCP-1 measurements appears to be useful in identifying the diagnosis of subtle renal vasculitis flare.

Serum uromodulin is associated with the severity of clinicopathological findings in ANCA-associated glomerulonephritis

Background

Uromodulin (UMOD), also known as Tamm-Horsfall protein, is a kidney-specific protein expressed by epithelial cells lining the thick ascending limb of the loop of Henle. In the current study, we aimed to clarify the clinical significance of UMOD in ANCA-associated glomerulonephritis (AAG).

Materials and methods

Sixty-one biopsy-proven AAG patients were included in this study. UMOD was measured using ELISA. The relationships between serum UMOD (sUMOD) levels and various clinicopathological findings were evaluated.

Results

AAG was classified into four categories (focal, crescentic, mixed, and sclerotic). In addition, tubulointerstitial lesions were classified as mild, moderate, and severe. The levels of sUMOD and urinary UMOD (uUMOD) were correlated with each other. A negative correlation between sUMOD levels and serum Cr levels, and positive correlation between sUMOD levels and eGFR were found. Patients in the high sUMOD group were associated with low serum Cr levels, focal classification, and mild tubulointerstitial injury compared to the low sUMOD group. Comparing the characteristics among histopathological classes, patients in the focal class had the best renal function and the highest levels of uUMOD/Cr and sUMOD. The focal class had significantly better renal survival compared with the severe histopathological classes (crescentic, mixed, and sclerotic). In univariate logistic regression analyses, prognostic factors for severe histopathological classes were low uUMOD/Cr, high serum Cr, and low sUMOD. Multivariate analyses revealed that low sUMOD predicted severe histopathological classes independent of serum Cr. The mean levels of sUMOD were significantly different between the focal class and severe histopathological classes, with a sensitivity of 70.6% and specificity of 90.0% (cut-off 143 ng/ml, AUC 0.80) by ROC curves.

Conclusion

Low sUMOD levels were associated with severe clinicopathological findings and might be considered as a risk factor for end stage renal disease in AAG.

Urinary Activin A is a novel biomarker reflecting renal inflammation and tubular damage in ANCA-associated vasculitis

Activin A, a member of the transforming growth factor-beta superfamily, is a critical modulator of inflammation and plays a key role in controlling the cytokine cascade that drives the inflammatory response. However, the role of activin A in inflammatory kidney diseases remains unknown. To address this issue, we examined here whether activin A can be detected in the kidney and/or urine from patients with antineutrophil cytoplasmic antibody (ANCA) -associated vasculitis (AAV). Fifty-one patients who had been diagnosed with AAV and were treated in our department between November 2011 to March 2018 were included in this study. Forty-one patients had renal complications (renal AAV). Serum and urinary activin A levels were measured by enzyme-linked immunosorbent assay. Correlation of urinary activin A concentration with clinical parameters was analyzed. Urinary activin A was undetectable in healthy volunteers. In contrast, urinary activin A concentration was significantly increased in patients with renal AAV but not in those with non-renal AAV. Urinary activin A concentration decreased rapidly after immunosuppressive treatment. There was a significant correlation of urinary activin A level with urinary protein, L-FABP, and NAG. Histologic evaluation revealed that urinary activin A levels were significantly higher in patients with cellular crescentic glomeruli than in those lacking this damage. In situ hybridization demonstrated that the mRNA encoding the activin A βA subunit was undetectable in normal kidneys but accumulated in the proximal tubules and crescentic glomeruli of the kidneys of patients with renal AAV. Immunostaining showed that activin A protein also was present in the proximal tubules, crescentic glomeruli, and macrophages infiltrating into the interstitium in the kidneys of patients with renal AAV. These data suggested that urinary activin A concentration reflects renal inflammation and tubular damage in AAV and may be a useful biomarker for monitoring renal AAV.

Evaluation of Potential Serum Biomarkers of Disease Activity in Diverse Forms of Vasculitis

OBJECTIVE

We evaluated potential circulating biomarkers of disease activity in giant cell arteritis (GCA), Takayasu arteritis (TA), polyarteritis nodosa (PAN), and eosinophilic granulomatosis with polyangiitis (EGPA).

METHODS

A panel of 22 serum proteins was tested in patients enrolled in the Vasculitis Clinical Research Consortium Longitudinal Studies of GCA, TA, PAN, or EGPA. Mixed models were used for most analyses. A J48 classification tree method was used to find the most relevant markers to differentiate between active and inactive GCA.

RESULTS

Tests were done on 418 samples from 152 patients (60 GCA, 29 TA, 26 PAN, 37 EGPA), during both active vasculitis and remission. In GCA, these showed significant (p < 0.05) differences between disease states: B cell-attracting chemokine 1 (BCA)-1/CXC motif ligand 13 (CXCL13), erythrocyte sedimentation rate (ESR), interferon-γ-induced protein 10/CXC motif chemokine 10, soluble interleukin 2 receptor α (sIL-2Rα), and tissue inhibitor of metalloproteinase-1 (TIMP-1). In EGPA, these showed significant increases during active disease: granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage-CSF, interleukin (IL)-6, IL-15, and sIL-2Rα. BCA-1/CXCL13 also showed such increases, but only after adjustment for treatment. In PAN, ESR and matrix metalloprotease (MMP)-3 showed significant differences between disease states. Differences in biomarker levels between diseases were significant for 11 markers and were more striking (all p < 0.01) than differences related to disease activity. A combination of lower values of TIMP-1, IL-6, interferon-γ, and MMP-3 correctly classified 87% of samples with inactive GCA.

CONCLUSION

We identified novel biomarkers of disease activity in GCA and EGPA. Differences of biomarker levels between diseases, independent of disease activity, were more apparent than differences related to disease activity. Further studies are needed to determine whether these serum proteins have potential for clinical use in distinguishing active disease from remission or in predicting longer-term outcomes.

From Renal Biomarkers to Therapeutic Targets: The Use of Monocyte Chemoattractant Protein 1, Transforming Growth Factor-Beta, and Connective Tissue Growth Factor in Diabetic Nephropathy and Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

In an ideal world, every condition would have a sensitive and specific marker that could be measured in a noninvasive or minimally invasive way. Instead, the medical community depends on invasive biomarkers, which carry inherent risks, to make a diagnosis and plan treatment. In this review article, the current state of research into biomarkers for a range of kidney diseases is discussed, beginning with those biomarkers that are already in clinical use and then moving to conditions for which no validated biomarker yet exists. This review focusses on diabetic nephropathy at the proteinuric end of the spectrum and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis at the nephritic end. An interesting feature is that the same biomarker, monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), has been identified as a potential target in both conditions, which suggests a shared pathogenic process that results in two very distinct clinical presentations. One of the major limiting features of research into this area, particularly for ANCA-associated vasculitis, is the recruitment of a sufficient number of patients to generate strong enough evidence to justify the biomarker’s routine use; this overlap in biomarkers may enable research in one condition to be applied more generally. In addition to their role as biomarkers, these molecules are also therapeutic targets, and some early research has been carried out to investigate this. Overall, this review brings together research from diverse fields to focus attention on the outstanding areas and the future areas that warrant further investigation.

Chemokine Receptor 8 Can Distinguish Antineutrophil Cytoplasmic Antibody-Associated Vasculitis From Infectious Complications

Introduction

Diagnosing vasculitis is frequently difficult because its clinical symptoms are similar to those of common infectious diseases and other inflammatory disorders. This study focused on chemokine receptor 8 (CCR8) in peripheral blood mononuclear cells to find a new biomarker that distinguishes vasculitis from infectious complications.

Methods

A cross-sectional study was conducted among 113 patients with systemic vasculitis who were referred to Japan Health Care Organization Sendai Hospital from 2014 to 2016, including those with antineutrophil cytoplasmic antibody (ANCA)−associated vasculitis, anti−glomerular basement membrane disease, lupus nephritis, and Henoch-Schonlein purpura. Peripheral blood mononuclear cells were extracted from blood, and CCR8 expression was examined by real time polymerase chain reaction and flow cytometry.

Results

CCR8 gene expression was significantly higher in patients with ANCA-associated vasculitis, which was confirmed by upregulated CCR8 protein expression in flow cytometry (P < 0.001 and P = 0.01, respectively). Neither lupus nephritis nor Henoch-Schonlein purpura showed upregulated CCR8. Elevated CCR8 in the active phase decreased significantly in remission (P = 0.002), which was correlated with decreased serum inflammatory markers. Despite elevated serological inflammatory markers, the CCR8 levels at the time of infection, including bacterial, viral, and fungal, did not increase, indicating that infectious complications did not affect CCR8 expression (P = 0.02).

Conclusion

CCR8 in peripheral blood mononuclear cells may be a useful diagnostic marker for ANCA-associated vasculitis to differentiate between active vasculitis and infectious inflammation.

[Kidney injury molecules (KIM-1, MCP-1) and type IV collagen in the assessment of activity of antineutrophil cytoplasmic antibody-associated glomerulonephritis]

AIM

To assess the significance of determining the serum and urinary concentrations of monocyte chemotactic protein-1 (MCP-1), kidney injury molecule-1 (KIM-1), and type IV collagen in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) to estimate the activity of renal involvement in AAV.

SUBJECTS AND METHODS

78 patients (32 men and 46 women) (median age 55 (45; 61) years) with AAV were examined. The patients were divided into 3 groups according to the AAV activity estimated using the Birmingham vasculitis activity Score (BVAS): 1) 25 patients with active ANCA-associated glomerulonephritis (GN); 2) 26 patients with active AAV without renal involvement; 3) 27 patients in sustained AAV remission. The serum and urinary concentrations of the markers were measured by enzyme immunoassay.

RESULTS

The urinary concentration of all 3 biomarkers was higher in patients with renal involvement (Group 1); the differences in the levels of MCP-1 and type IV collagen were statistically significant as compared to Groups 2 and 3 (p<0.01), while that in KIM-1 level was only in Group 2. There were statistically significant correlations between the urinary concentration of these biomarkers and the traditional GN activity indices (erythrocyturia, daily proteinuria (DPU), total BVAS scores that reflect renal involvement, as well as serum creatinine levels and estimated glomerular filtration rate (p<0.05). ROC curve analysis showed that the urinary MCP-1 excretion of ≥159 pg/ml had the highest (92%) sensitivity and urinary type IV collagen excretion of ≥3.09 µg/l had the highest (86%) specificity in assessing the activity of ANCA-associated GN. At the same time, their diagnostic value increased in terms of a combination of DPU and ESR (96% sensitivity, 84.9% specificity).

CONCLUSION

The urinary excretion of MCP-1, KIM-1, and type IV collagen reflects the severity of local renal inflammation in AAV patients and a study of these indicators is a promising diagnostic tool for assessing the activity of ANCA-associated GN.

ANCA-positive vasculitis: Clinical implications of ANCA types and titers

INTRODUCTION

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is an autoimmune disease that can affect multiple organs, the kidney being one of the most affected. Apart from the diagnostics value of ANCA, they have also been advocated as biomarkers of the disease activity. Recently, the genetic changes found in polyangiitis associated with serine-protease proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA raised the possibility of immune-pathogenic and therapeutic differences.

OBJECTIVE

To identify differences in the number of relapses, inflammatory markers, outcomes and renal histology related to the types of ANCA. To analyze the implications of ANCA titers in prognosis.

METHOD

A retrospective observational study in a Portuguese tertiary hospital.

RESULTS

There were no differences in the progression of renal function, histological pattern and initial treatment with regard to ANCA subtypes. As for the evaluated parameters, there were no significant differences according to the types of ANCA, except for mean CRP values within the normal range, which was 6.3±1.3 mg/L for MPO-ANCA and 12.4±10.14 mg/L for PR3-ANCA (p=0.04). We found that 66.7% of the MPO-ANCA-positive showed no relapses versus 40% in the case of PR3-ANCA-positive. There was no correlation between the ANCA titers at presentation, during remission, and in the last evaluation, and the number of relapses.

CONCLUSION

PR3-ANCA patients have a mean CRP value within the normal range significantly higher than that of MPO-ANCA patients (p=0.04), which seems to reveal greater inflammatory activity in the first.

The prognostic significance of the Birmingham Vasculitis Activity Score (BVAS) with systemic vasculitis patients transferred to the intensive care unit (ICU)

Systemic vasculitides represent a heterogeneous group of diseases that share clinical features including respiratory distress, renal dysfunction, and neurologic disorders. These diseases may often cause life-threatening complications requiring admission to an intensive care unit (ICU). The aim of the study was to evaluate the validity and responsiveness of Birmingham Vasculitis Activity Score (BVAS) score to predict survival in patients with systemic vasculitides admitted to ICU.A retrospective study was carried out from 2004 to 2014 in 18 patients with systemic vasculitis admitted to 2 different Rheumatology divisions and transferred to ICU due to clinical worsening, with a length of stay beyond 24 hours. We found that ICU mortality was significantly associated with higher BVAS scores performed in the ward (P = 0.01) and at the admission in ICU (P = 0.01), regardless of the value of Acute Physiology And Chronic Health Evaluation (APACHE II) scores (P = 0.50). We used receiver-operator characteristic (ROC) curve analysis to evaluate the possible cutoff value for the BVAS in the ward and in ICU and we found that a BVAS > 8 in the ward and that a BVAS > 10 in ICU might be a useful tool to predict in-ICU mortality.BVAS appears to be an excellent tool for assessing ICU mortality risk of systemic vasculitides patients admitted to specialty departments. Our experience has shown that performing the assessment at admission to the ward is more important than determining the evaluation before the clinical aggravation causing the transfer to ICU.

Current and novel biomarkers in anti-neutrophil cytoplasm-associated vasculitis

Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) is characterized by a variable disease course, with up to 50% of patients having one relapse within 5 years and many progressing to end-stage organ damage despite modern treatment strategies. Moreover, complications arising from treatment dominate the causes of mortality and morbidity both early and late during disease, especially in the elderly and those with severe renal involvement, and there is additional uncertainty as to how long treatment should be continued. There is, therefore, an urgent clinical need to identify robust biomarkers to better predict treatment responses, risk of disease relapse and eventual complete clinical and immunological quiescence. To date, no such biomarkers exist, but better understanding of disease pathogenesis and the underlying immune dysfunction has provided some potential candidates linked to the discovery of new antibodies, different leukocyte activation states, the role of the alternative complement pathway and markers of vascular activation. With all promising new biomarkers, there is the need to rapidly replicate and validate early findings using large biobanks of samples that could be brought together by leaders in the field.

Urinary Soluble CD163 in Active Renal Vasculitis

A specific biomarker that can separate active renal vasculitis from other causes of renal dysfunction is lacking, with a kidney biopsy often being required. Soluble CD163 (sCD163), shed by monocytes and macrophages, has been reported as a potential biomarker in diseases associated with excessive macrophage activation. Thus, we hypothesized that urinary sCD163 shed by crescent macrophages correlates with active glomerular inflammation. We detected sCD163 in rat urine early in the disease course of experimental vasculitis. Moreover, microdissected glomeruli from patients with small vessel vasculitis (SVV) had markedly higher levels of CD163 mRNA than did those from patients with lupus nephritis, diabetic nephropathy, or nephrotic syndrome. Both glomeruli and interstitium of patients with SVV strongly expressed CD163 protein. In 479 individuals, including patients with SVV, disease controls, and healthy controls, serum levels of sCD163 did not differ between the groups. However, in an inception cohort, including 177 patients with SVV, patients with active renal vasculitis had markedly higher urinary sCD163 levels than did patients in remission, disease controls, or healthy controls. Analyses in both internal and external validation cohorts confirmed these results. Setting a derived optimum cutoff for urinary sCD163 of 0.3 ng/mmol creatinine for detection of active renal vasculitis resulted in a sensitivity of 83%, specificity of 96%, and a positive likelihood ratio of 20.8. These data indicate that urinary sCD163 level associates very tightly with active renal vasculitis, and assessing this level may be a noninvasive method for diagnosing renal flare in the setting of a known diagnosis of SVV.

Significance of CD163-Positive Macrophages in Proliferative Glomerulonephritis

BACKGROUND

CD163, a marker of M2 macrophages, possesses anti-inflammatory properties. This study aims to investigate the clinicopathological significance of CD163-positive macrophages in proliferative glomerulonephritis.

METHODS

Renal tissue samples from patients with lupus nephritis (LN, n = 22), antineutrophil cytoplasmic autoantibody (ANCA)-associated pauci-immune necrotizing glomerulonephritis (PNGN, n = 10), type 1 membranoproliferative glomerulonephritis (n = 5), minimal change disease (n = 8) and normal control kidneys (n = 3) were included in this study. The expression of CD163, CD68, CD20 and CD3 in renal tissues was detected by immunohistochemistry or immunofluorescence. The level of urinary neutrophil gelatinase-associated lipocalin (NGAL) was determined by enzyme-linked immunosorbent assay.

RESULTS

CD163 was mainly expressed in active crescentic glomerulonephritis, proliferative glomerular lesions and areas of tubulointerstitial injury. Patients with LN-IV and PNGN had numerous CD163-positive cells in glomerular and acute tubulointerstitial lesions. CD163-positive cells in glomeruli positively correlated to proteinuria yet negatively correlated to estimated glomerular filtration rate. There was a positive correlation between the number of CD163 cells in acute tubulointerstitial lesions and NGAL levels, whereas a negative correlation between CD163 numbers and estimated glomerular filtration rate. The number of CD163-positive cells in crescentic glomerulonephritis was more than other groups. In LN, the number of CD163 cells in the tubulointerstitial and glomerular lesions had a positive correlation with activity index. Dual staining showed that CD163-positive cells also expressed CD68, although they did not show any staining for CD20 or CD3.

CONCLUSIONS

CD163-positive macrophages were involved in the pathogenesis of proliferative glomerular lesions, active crescentic glomerulonephritis and acute tubular injury of patients with PNGN and active LN.

Evaluation and validation of biomarkers in granulomatosis with polyangiitis and microscopic polyangiitis

BACKGROUND

Studies in anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) have revealed promising biomarkers. The aim of our study was to validate the most encouraging markers of granulomatosis with polyangiitis and microscopic polyangiitis identified by literature search and to create biomarker panels.

METHODS

A systematic literature review was performed and we identified 161 marker molecules that were ranked by their quantitative differential expression between active and inactive disease. Enzyme-linked immunosorbent assays were used to validate the results in a cross-sectional cohort of patients with renal involvement. Active vasculitis as assessed by the Birmingham Vasculitis Score version 3 (BVAS v3) was defined as BVAS v3 ≥1 and inactive disease as BVAS v3 = 0. Statistical analysis was performed with SPSS version 21 and the Salford Predictive Modeler 7.0 was used to generate a predictive biomarker panel.

RESULTS

The review indicated abundant expression of sC5bC9, C3a, C5a and monocyte chemotactic protein (MCP)-1 in urine, whereas granulocyte macrophage colony-stimulating factor, C-reactive protein (CRP), soluble fms-like tyrosine kinase-1, interleukin-17A (IL-17A), C5a, hyaluronan, C3a and interleukin-18 binding protein (IL-18BP) were identified to be highly diverse in active and inactive disease in blood samples. Our cross-sectional analysis revealed significant up-regulation of CRP, C5a, C3a, IL-18BP in blood and C5a and MCP-1 in urine samples during active AAV (all P < 0.05). Creation of a biomarker panel comprising CRP and urinary MCP-1 yielded a sensitivity and specificity of 76% (area under the curve 0.89).

CONCLUSIONS

We identified promising biomarkers in a literature-based review that were in part corroborated as has been shown for CRP, C3a, C5a, IL-18BP in blood and MCP-1 and C5a in urine samples. Moreover, we propose a biomarker panel comprising CRP and urinary MCP-1 in patients with AAV and renal involvement. Further investigations to confirm our preliminary results are clearly warranted, including the reliability to predict disease relapses.

Are urinary levels of high mobility group box 1 markers of active nephritis in anti-neutrophil cytoplasmic antibody-associated vasculitis?

The objective of this study is to evaluate urinary high mobility group box 1 (HMGB1) levels as markers for active nephritis in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) in comparison with urinary CD4(+) effector memory T cells and urinary monocyte chemoattractant protein-1 (MCP-1). Twenty-four AAV patients with active nephritis and 12 healthy controls (HC) were evaluated. In nine patients, samples were also obtained during remission. Urinary levels of HMGB1 were measured by Western blot. CD4(+) T cells and CD4(+) effector memory T cells (CD4(+) CD45RO(+) CCR7(-) ) were determined in urine and whole blood by flow cytometry. Measurement of urinary levels of MCP-1 and serum HMGB1 levels were performed by enzyme-linked immunosorbent assay (ELISA). AAV patients with active nephritis had higher median intensity of HMGB1 in urine than HC [10·3 (7·05-18·50) versus 5·8 (4·48-7·01); P = 0·004]. Both urinary HMGB1 and MCP-1 levels decreased significantly from active nephritis to remission. The urinary MCP-1/creatinine ratio correlated with Birmingham Vasculitis Activity Score (BVAS) (P = 0·042). No correlation was found between the HMGB1/creatinine ratio and 24-h proteinuria, estimated glomerular filtration rate (eGFR), MCP-1/creatinine ratio, BVAS and serum HMGB1. A positive correlation was found between urinary HMGB1/creatinine ratio and CD4(+) T cells/creatinine ratio (P = 0·028) and effector memory T cells/creatinine ratio (P = 0·039) in urine. Urinary HMGB1 levels are increased in AAV patients with active nephritis when compared with HC and patients in remission, and urinary HMGB1 levels are associated with CD4(+) T cells and CD4(+) effector memory T cells in urine. Measurement of urinary HMGB1 may be of additional value in identifying active glomerulonephritis in AAV patients.

Renal redox dysregulation in AKI: application for oxidative stress marker of AKI

Oxidative stress is a major determinant of acute kidney injury (AKI); however, the effects of an AKI on renal redox system are unclear, and few existing AKI markers are suitable for evaluating oxidative stress. We measured urinary levels of the redox-regulatory protein thioredoxin 1 (TRX1) in patients with various kinds of kidney disease and in mice with renal ischemia-reperfusion injury. Urinary TRX1 levels were markedly higher in patients with AKI than in those with chronic kidney disease or in healthy subjects. In a receiver operating characteristic curve analysis to differentiate between AKI and other renal diseases, the area under the curve for urinary TRX1 was 0.94 (95% confidence interval, 0.90-0.98), and the sensitivity and specificity were 0.88 and 0.88, respectively, at the optimal cutoff value of 43.0 μg/g creatinine. Immunostaining revealed TRX1 to be diffusely distributed in the tubules of normal kidneys, but to be shifted to the brush borders or urinary lumen in injured tubules in both mice and humans with AKI. Urinary TRX1 in AKI was predominantly in the oxidized form. In cultured human proximal tubular epithelial cells, hydrogen peroxide specifically and dose dependently increased TRX1 levels in the culture supernatant, while reducing intracellular levels. These findings suggest that urinary TRX1 is an oxidative stress-specific biomarker useful for distinguishing AKI from chronic kidney disease and healthy kidneys.

Biomarkers in vasculitis

PURPOSE OF REVIEW

Better biomarkers are needed for guiding management of patients with vasculitis. Large cohorts and technological advances had led to an increase in preclinical studies of potential biomarkers.

RECENT FINDINGS

The most interesting markers described recently include a gene expression signature in CD8+ T cells that predicts tendency to relapse or remain relapse-free in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and a pair of urinary proteins that are elevated in Kawasaki disease but not other febrile illnesses. Both of these studies used 'omics' technologies to generate and then test hypotheses. More conventional hypothesis-based studies have indicated that the following circulating proteins have potential to improve upon clinically available tests: pentraxin-3 in giant cell arteritis and Takayasu's arteritis; von Willebrand factor antigen in childhood central nervous system vasculitis; eotaxin-3 and other markers related to eosinophils or Th2 immune responses in eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome); and matrix metalloproteinase-3, tissue inhibitor of metalloproteinase-1, and CXCL13 in ANCA-associated vasculitis.

SUMMARY

New markers testable in blood and urine have the potential to assist with diagnosis, staging, assessment of current disease activity, and prognosis. However, the standards for clinical usefulness, in particular, the demonstration of either very high sensitivity or very high specificity have yet to be met for clinically relevant outcomes.

Urinary concentration of monocyte chemoattractant protein-1 in idiopathic glomerulonephritis: a long-term follow-up study

Background

Monocyte chemoattractant protein-1 (MCP-1), which is up regulated in kidney diseases, is considered a marker of kidney inflammation. We examined the value of urine MCP-1 in predicting the outcome in idiopathic glomerulonephritis.

Methods

Between 1993 and 2004, 165 patients (68 females) diagnosed with idiopathic proteinuric glomerulopathy and with serum creatinine <150 µmol/L at diagnosis were selected for the study. Urine concentrations of MCP-1 were analyzed by ELISA in early morning spot urine samples collected on the day of the diagnostic kidney biopsy. The patients were followed until 2009. The progression rate to end-stage kidney disease was calculated using Kaplan–Meier survival analysis. End-stage kidney disease (ESKD) was defined as the start of kidney replacement therapy during the study follow-up time.

Results

Patients with proliferative glomerulonephritis had significantly higher urinary MCP-1 excretion levels than those with non-proliferative glomerulonephritis (p<0.001). The percentage of patients whose kidney function deteriorated significantly was 39.0% in the high MCP-1 excretion group and 29.9% in the low MCP-1 excretion group. However, after adjustment for confounding variables such as glomerular filtration rate (GFR) and proteinuria, there was no significant association between urine MCP-1 concentration and progression to ESKD, (HR = 1.75, 95% CI = 0.64–4.75, p = 0.27).

Conclusion

Our findings indicate that progression to end-stage kidney disease in patients with idiopathic glomerulopathies is not associated with urine MCP-1 concentrations at the time of diagnosis.