Repeat renal biopsy improves the Oxford classification-based prediction of immunoglobulin A nephropathy outcome.

BACKGROUND: The prognosis of IgA nephropathy (IgAN) is very heterogeneous. Predicting the nature and the rate of the disease progression is crucial for refining patient treatment. The aim of this study was to evaluate the prognostic impact of an Oxford classification-based repeat kidney tissue evaluation to predict end-stage renal disease (ESRD). METHODS: Patients with biopsy-proven primary IgAN who underwent two renal biopsies at our centre were analyzed retrospectively. Renal biopsies were scored by two pathologists blinded to the clinical data and according to the updated Oxford classification. Cox models were generated to evaluate the prognostic impact considering the Oxford classification elementary lesions from the first (Model 1) or the second (Model 2) biopsy, adjusted on clinical data at time of reevaluation. The prognostic impacts of the dynamic evolution of each elementary lesion between biopsies were also assessed through univariate and multivariate evaluation. RESULTS: A total of 168 adult patients were included, with a median follow-up duration of 18 (range 11-24) years. The second biopsy was performed either systematically (n = 112) of for-cause (n = 56), after a median time of 5.4 years. The prognostic performances of Model 2 (second biopsy) were significantly better than Model 1 (first biopsy, analysis of deviance P < 0.0001). The dynamic changes of C and T lesions were significantly associated with the progression toward ESRD after adjustment on variables from Model 2. CONCLUSION: Both static and dynamic Oxford-based histological evaluation offered by a repeat biopsy improves the prediction of ESRD in patients with IgAN.

GWAS for serum galactose-deficient IgA1 implicates critical genes of the O-glycosylation pathway.

Aberrant O-glycosylation of serum immunoglobulin A1 (IgA1) represents a heritable pathogenic defect in IgA nephropathy, the most common form of glomerulonephritis worldwide, but specific genetic factors involved in its determination are not known. We performed a quantitative GWAS for serum levels of galactose-deficient IgA1 (Gd-IgA1) in 2,633 subjects of European and East Asian ancestry and discovered two genome-wide significant loci, in C1GALT1 (rs13226913, P = 3.2 x 10-11) and C1GALT1C1 (rs5910940, P = 2.7 x 10-8). These genes encode molecular partners essential for enzymatic O-glycosylation of IgA1. We demonstrated that these two loci explain approximately 7% of variability in circulating Gd-IgA1 in Europeans, but only 2% in East Asians. Notably, the Gd-IgA1-increasing allele of rs13226913 is common in Europeans, but rare in East Asians. Moreover, rs13226913 represents a strong cis-eQTL for C1GALT1 that encodes the key enzyme responsible for the transfer of galactose to O-linked glycans on IgA1. By in vitro siRNA knock-down studies, we confirmed that mRNA levels of both C1GALT1 and C1GALT1C1 determine the rate of secretion of Gd-IgA1 in IgA1-producing cells. Our findings provide novel insights into the genetic regulation of O-glycosylation and are relevant not only to IgA nephropathy, but also to other complex traits associated with O-glycosylation defects, including inflammatory bowel disease, hematologic disease, and cancer.

Deletion Variants of CFHR1 and CFHR3 Associate with Mesangial Immune Deposits but Not with Progression of IgA Nephropathy.

Activation of complement through the alternative pathway has a key role in the pathogenesis of IgA nephropathy (IgAN). Large, international, genome-wide association studies have shown that deletion of complement factor H-related genes 1 and 3 (CFHR3,1Δ) is associated with a reduced risk of developing IgAN, although the prognostic value of these deletions in IgAN remains unknown. Here, we compared the renal outcomes of patients with IgAN according to their CFHR3,1Δ genotype. This retrospective, monocentric cohort study included 639 white patients with biopsy-proven IgAN since 1979 (mean age at diagnosis, 40.1 years; median follow-up, 132 months). We determined the number of CFHR3 and CFHR1 gene copies by quantitative PCR and collected clinical and biologic data by reviewing the patients' medical records. In all, 30.5% of the patients were heterozygous and 4% were homozygous for CFHR3,1Δ We did not detect an association between CFHR3,1Δ and age, eGFR, urinary protein excretion rate, or the presence of hypertension or hematuria at the time of diagnosis. The mean intensities of immune IgA, IgG, and C3 deposits were lower in the group with heterozygous or homozygous gene deletions than in those with no deletion. However, CFHR3,1Δ did not associate with progression to stage 3 CKD or renal death. In conclusion, the CFHR3,1Δ genotype did not associate with progression toward CKD stages 3 and 5 in our white population of patients with IgAN, although it did associate with a reduced level of glomerular immune deposits.

Prognostic Value of Serum Biomarkers of Autoimmunity for Recurrence of IgA Nephropathy after Kidney Transplantation.

A prognostic biomarker for IgA nephropathy (IgAN) recurrence after renal transplant is lacking. We followed 96 consecutive first renal transplant recipients with native kidney IgAN (79 men; 92 deceased donors; mean age =48.1 years) on calcineurin inhibitor-based immunosuppression over 10 years for death, allograft failure, and clinicopathologic recurrence (CPR; clinically evident and biopsy-proven). Using time-dependent Cox regression analysis and receiver operating characteristic curves, we assessed prognostic significance of levels of galactose-deficient IgA1 (Gd-IgA1; autoantigen) and Gd-IgA1-specific IgG and IgA autoantibodies in serum obtained at time of transplant or native-kidney IgAN diagnosis (30 patients only). Overall, 13 patients died, 34 kidneys failed (17 due to CPR), and 34 patients developed CPR after a mean interval of 5.8 years. Compared with healthy controls (n=30), patients had significantly elevated serum Gd-IgA1 levels at diagnosis and transplant, but levels did not associate with any outcome. Patients also had significantly elevated levels of normalized (but not total) serum Gd-IgA1-specific IgG autoantibodies at diagnosis and transplant, and the level at transplant associated with higher risk of CPR (relative risk, 2.68; 95% confidence interval, 1.26 to 5.71; P=0.01; area under the receiver operating characteristic curve, 0.62; 95% confidence interval, 0.51 to 0.74; P=0.05). Normalized Gd-IgA1-specific IgG autoantibody level remained an independent risk factor for CPR in multivariate analysis. Serum Gd-IgA1-specific IgA autoantibody level did not change between diagnosis and transplant or predict outcome. This study emphasizes post-transplant prognostic value of normalized serum IgG antiglycan autoantibody level in patients with IgAN.

Geographic differences in genetic susceptibility to IgA nephropathy: GWAS replication study and geospatial risk analysis.

IgA nephropathy (IgAN), major cause of kidney failure worldwide, is common in Asians, moderately prevalent in Europeans, and rare in Africans. It is not known if these differences represent variation in genes, environment, or ascertainment. In a recent GWAS, we localized five IgAN susceptibility loci on Chr.6p21 (HLA-DQB1/DRB1, PSMB9/TAP1, and DPA1/DPB2 loci), Chr.1q32 (CFHR3/R1 locus), and Chr.22q12 (HORMAD2 locus). These IgAN loci are associated with risk of other immune-mediated disorders such as type I diabetes, multiple sclerosis, or inflammatory bowel disease. We tested association of these loci in eight new independent cohorts of Asian, European, and African-American ancestry (N = 4,789), followed by meta-analysis with risk-score modeling in 12 cohorts (N = 10,755) and geospatial analysis in 85 world populations. Four susceptibility loci robustly replicated and all five loci were genome-wide significant in the combined cohort (P = 5×10⁻³²-3×10⁻¹°), with heterogeneity detected only at the PSMB9/TAP1 locus (I²â€Š= 0.60). Conditional analyses identified two new independent risk alleles within the HLA-DQB1/DRB1 locus, defining multiple risk and protective haplotypes within this interval. We also detected a significant genetic interaction, whereby the odds ratio for the HORMAD2 protective allele was reversed in homozygotes for a CFHR3/R1 deletion (P = 2.5×10⁻4). A seven-SNP genetic risk score, which explained 4.7% of overall IgAN risk, increased sharply with Eastward and Northward distance from Africa (r = 0.30, P = 3×10⁻¹²8). This model paralleled the known East-West gradient in disease risk. Moreover, the prediction of a South-North axis was confirmed by registry data showing that the prevalence of IgAN-attributable kidney failure is increased in Northern Europe, similar to multiple sclerosis and type I diabetes. Variation at IgAN susceptibility loci correlates with differences in disease prevalence among world populations. These findings inform genetic, biological, and epidemiological investigations of IgAN and permit cross-comparison with other complex traits that share genetic risk loci and geographic patterns with IgAN.

Overweight/obesity revisited as a predictive risk factor in primary IgA nephropathy.

BACKGROUND: The absolute renal risk (ARR) of dialysis/death in IgA nephropathy (IgAN) was based on three major, independent equipotent risk factors: hypertension, proteinuria ≥1 g/day and severe pathological score at diagnosis. We studied, in our prospective regional cohort of IgAN, the impact of body mass index (BMI) on the ultimate outcome in light of this ARR concept. METHODS: We had information on 331 IgAN patients (233 men). At diagnosis, the BMI was normal (<25 kg/m(2)) in 195 and elevated (≥25) in 136 (44.1%) with 102 overweight (25-29.9) and 34 obese (≥35) defining two groups, normal BMI and elevated BMI, subsequently compared. RESULTS: At diagnosis, in the overweight/obese group, hypertension and proteinuria ≥1 g/day were more frequent (respectively, P < 0.0001 and P = 0.0006) and the mean global optical score was increased (P = 0.002). This resulted in a worse ARR scoring distribution (P < 0.0001). In addition, these patients with an elevated BMI were ∼10 years older (P < 0.0001), including more obese women and with an eGFR already lower (P = 0.0003). At last follow-up, in the overweight/obese group, progression remained worse with greater prevalence of CKD-3+ (43.4 versus 21.0%; P < 0.0001) and dialysis/death events (21.3 versus 13.9%). Kaplan-Meier survival and Cox regression analyses demonstrated that ARR remained a powerful independent risk factor for prediction of events, but not BMI. CONCLUSIONS: IgAN patients with an elevated BMI at diagnosis had a significantly worse presentation and worse final outcome. Overweight/obesity increased hypertension frequency, proteinuria level and some renal lesions all of which translate into a worse ARR for prediction of CKD-3+ or dialysis alone or dialysis/death, with no apparent direct effect of BMI per se.

Validation of the absolute renal risk of dialysis/death in adults with IgA nephropathy secondary to Henoch-Schönlein purpura: a monocentric cohort study.

BACKGROUND: We established earlier the absolute renal risk (ARR) of dialysis/death (D/D) in primary IgA nephropathy (IgAN) which permitted accurate prospective prediction of final prognosis. This ARR was based on the potential presence at initial diagnosis of three major, independent, and equipotent risk factors such as hypertension, quantitative proteinuria≥1 g per day, and severe pathological lesions appreciated by our local classification scoring≥8 (range 0-20). We studied the validity of this ARR concept in secondary IgAN to predict future outcome and focused on Henoch-Schönlein purpura (HSP) nephritis. METHODS: Our cohort of adults IgAN concerned 1064 patients with 101 secondary IgAN and was focused on 74 HSP (59 men) with a mean age of 38.6 at initial diagnosis and a mean follow-up of 11.8 years. Three major risk factors: hypertension, proteinuria≥1 g/d, and severe pathological lesions appreciated by our global optical score≥8 (GOS integrated all elementary histological lesions), were studied at biopsy-proven diagnosis and their presence defined the ARR scoring: 0 for none present, 3 for all present, 1 or 2 for the presence of any 1 or 2 risk factors. The primary end-point was composite with occurrence of dialysis or death before (D/D). We used classical statistics and both time-dependent Cox regression and Kaplan-Meier survival curve methods. RESULTS: The cumulative rate of D/D at 10 and 20 years post-onset was respectively 0 and 14% for ARR=0 (23 patients); 10 and 23% for ARR=1 (N=19); 27 and 33% for ARR=2 (N=24); and 81 and 100% (before 20 y) in the 8 patients with ARR=3 (P=0.0007). Prediction at time of diagnosis (time zero) of 10y cumulative rate of D/D event was 0% for ARR=0, 10% for ARR=1, 33% for ARR=2, and 100% by 8.5y for ARR=3 (P=0.0003) in this adequately treated cohort. CONCLUSION: This study clearly validates the Absolute Renal Risk of Dialysis/Death concept in a new cohort of HSP-IgAN with utility to individual management and in future clinical trials.

Autoantibodies targeting galactose-deficient IgA1 associate with progression of IgA nephropathy.

Mesangial and circulating IgA1 with aberrantly glycosylated hinge region O-glycans characterize IgA nephropathy (IgAN). Unlike healthy individuals, some IgA1 is galactose deficient in patients with IgAN, leaving terminal N-acetylgalactosamine residues in the hinge region exposed. Circulating autoantibodies that recognize such galactose-deficient IgA1 as an autoantigen, or the levels of the autoantigen itself, may allow prediction of disease progression. Here, we analyzed serum samples obtained at diagnosis for autoantigen and autoantibodies from 97 patients with IgAN selected from our prospective cohort according to their absolute renal risk for progression to dialysis or death (0, very low; 1, low; 2, high; 3, very high). We also analyzed samples from controls comprising 30 healthy volunteers and 30 patients with non-IgAN disease. The mean follow-up was 13.8 years. We found that mean serum levels of total autoantigen, normalized IgG autoantibody, and total IgA autoantibody were significantly higher in patients than in the combined controls (all P≤0.01). Furthermore, increasing levels correlated with worse clinical outcomes. In Cox regression and Kaplan-Meier analyses, IgG autoantibody levels ≥1.33 predicted dialysis or death (both P≤0.01). In conclusion, these data suggest that serum levels of IgG and IgA autoantibodies strongly associate with the progression of IgAN nephropathy.

Genome-wide association analyses define pathogenic signaling pathways and prioritize drug targets for IgA nephropathy.

IgA nephropathy (IgAN) is a progressive form of kidney disease defined by glomerular deposition of IgA. Here we performed a genome-wide association study of 10,146 kidney-biopsy-diagnosed IgAN cases and 28,751 controls across 17 international cohorts. We defined 30 genome-wide significant risk loci explaining 11% of disease risk. A total of 16 loci were new, including TNFSF4/TNFSF18, REL, CD28, PF4V1, LY86, LYN, ANXA3, TNFSF8/TNFSF15, REEP3, ZMIZ1, OVOL1/RELA, ETS1, IGH, IRF8, TNFRSF13B and FCAR. The risk loci were enriched in gene orthologs causing abnormal IgA levels when genetically manipulated in mice. We also observed a positive genetic correlation between IgAN and serum IgA levels. High polygenic score for IgAN was associated with earlier onset of kidney failure. In a comprehensive functional annotation analysis of candidate causal genes, we observed convergence of biological candidates on a common set of inflammatory signaling pathways and cytokine ligand-receptor pairs, prioritizing potential new drug targets.

Single nucleotidic polymorphism 844 A->G of FCAR is not associated with IgA nephropathy in Caucasians.

BACKGROUND: IgA nephropathy is characterized by a high heterogeneity of clinical expression with 10-30% of patients progressing to end-stage renal failure. The gene of the FcαRI or CD89 presents a single-nucleotide polymorphism responsible for a proinflammatory phenotype of neutrophils in vitro and ex vivo. The aim of our study was to assess whether this CD89 polymorphism 844 A->G is (i) a marker of disease susceptibility and/or (ii) associated with a more severe prognosis. METHODS: All patients diagnosed with IgA nephropathy and for whom DNA frozen sample was available were included in this European monocentric retrospective analysis and compared to a cohort of healthy volunteers. Allelic discrimination was performed by real-time quantitative polymerase chain reaction (Applied Biosystems™). We first compared the distribution of A and G alleles between patients and volunteers and then studied the relationships between alleles and renal survival, histological score, proteinuria and renal function at diagnosis. RESULTS: Seven hundred and twenty-six patients were analyzed for the study of susceptibility and 425 in the association study. The presence of the G allele was not associated with the occurrence of IgA nephropathy (χ(2) test 0.57, ns). Likewise, renal survival and the criteria for disease activity at time of diagnosis were not affected by the presence of the G allele. CONCLUSIONS: No significant association between 844 A->G CD89 polymorphism and the expression of the IgA nephropathy in Caucasians exists. This result does, however, not preclude the implication of other CD89 polymorphisms neither the possibility for a role of CD89 in the pathogenesis of IgA nephropathy.

Mycophenolate sodium dosing in combination with tacrolimus: pharmacokinetic evaluation of a novel regimen in de novo tacrolimus-treated kidney transplant patients.

BACKGROUND: There are no clear guidelines concerning the appropriate dose of mycophenolate acid (MPA) to be used in association with tacrolimus. When MPA is given at an approved fixed dose in cyclosporine-treated patients, initial systemic under exposure is frequent and associated with the occurrence of acute rejection. We pharmacologically evaluated in tacrolimus-treated recipients a novel dosing regimen of MPA with an initial high dose followed by a gradual decrease over time. METHODS: 15 de novo tacrolimus-treated kidney transplant patients were administered mycophenolate sodium at the dose of 720 mg b.i.d. for the first week post-transplant, 540 mg b.i.d. until Day 30, and then 360 mg b.i.d. until Day 90. MPA exposure was evaluated by the 12 h area under MPA concentration versus time curve (AUC) determined at Days 2, 7, 15, 30 and 90 post-transplant. RESULTS: Median MPA AUC was constantly within the therapeutic window of 30 - 60 mg/l × h throughout the three months of evaluation. More than 75% of patients had a MPA AUC above 30 mg/l × h at Day 2 and Day 7 post-transplant. CONCLUSION: This exploratory study suggests that such a dosing regimen of mycophenolate sodium might quickly offer and sustain an optimal exposure to MPA in tacrolimus-treated kidney transplant patients.

Predicting the risk for dialysis or death in IgA nephropathy.

For the individual patient with primary IgA nephropathy (IgAN), it remains a challenge to predict long-term outcomes for patients receiving standard treatment. We studied a prospective cohort of 332 patients with biopsy-proven IgAN patients followed over an average of 13 years. We calculated an absolute renal risk (ARR) of dialysis or death by counting the number of risk factors present at diagnosis: hypertension, proteinuria ≥1 g/d, and severe pathologic lesions (global optical score, ≥8). Overall, the ARR score allowed significant risk stratification (P < 0.0001). The cumulative incidence of death or dialysis at 10 and 20 years was 2 and 4%, respectively, for ARR=0; 2 and 9% for ARR=1; 7 and 18% for ARR=2; and 29 and 64% for ARR=3, in adequately treated patients. When achieved, control of hypertension and reduction of proteinuria reduced the risk for death or dialysis. In conclusion, the absolute renal risk score, determined at diagnosis, associates with risk for dialysis or death.

The Oxford IgA nephropathy clinicopathological classification is valid for children as well as adults.

To study the predictive value of biopsy lesions in IgA nephropathy in a range of patient ages we retrospectively analyzed the cohort that was used to derive a new classification system for IgA nephropathy. A total of 206 adults and 59 children with proteinuria over 0.5 g/24 h/1.73 m(2) and an eGFR of stage-3 or better were followed for a median of 69 months. At the time of biopsy, compared with adults children had a more frequent history of macroscopic hematuria, lower adjusted blood pressure, and higher eGFR but similar proteinuria. Although their outcome was similar to that of adults, children had received more immunosuppressants and achieved a lower follow-up proteinuria. Renal biopsies were scored for variables identified by an iterative process as reproducible and independent of other lesions. Compared with adults, children had significantly more mesangial and endocapillary hypercellularity, and less segmental glomerulosclerosis and tubulointerstitial damage, the four variables previously identified to predict outcome independent of clinical assessment. Despite these differences, our study found that the cross-sectional correlation between pathology and proteinuria was similar in adults and children. The predictive value of each specific lesion on the rate of decline of renal function or renal survival in IgA nephropathy was not different between children and adults.

Creatinine-based GFR predicting equations in renal transplantation: reassessing the tubular secretion effect.

BACKGROUND: The real utility of blocking the tubular secretion of creatinine with cimetidine in order to ameliorate the prediction of renal graft function is questionable, particularly in the context of an increasing diffusion of the Modification of Diet in Renal Disease (MDRD) study equation. We have compared the impact of cimetidine on the performances of the Cockcroft-Gault (C-G) and MDRD equations in 56 renal transplant patients with an estimated glomerular filter rate (GFR) >30 mL/min/1.73 m(2) for whom true GFR was directly measured by inulin clearance. METHODS: Serum creatinine concentration (SCr) was measured [isotope dilution mass spectrometry (IDMS) traceable enzymatic assay] at the beginning of the inulin clearance procedure and 2 days later, after three oral cimetidine doses of 800 mg every 12 h. Predictive and diagnostic performances of the re-expressed MDRD and C-G formulas were compared before and after cimetidine intake. RESULTS: Mean SCr (+/-SD) increased from 120 micromol/L (+/-34) before to 154 micromol/L (+/-47) after cimetidine. The beneficial effect of cimetidine was significant only on the accuracy of the C-G formula (accuracy 30% post-cimetidine of 93 and 79% for the C-G and MDRD equations, respectively). Likewise, while a higher proportion of patients were correctly staged using the chronic kidney disease classification after cimetidine with the C-G equation (59% before and 68% after), no improvement was seen with the MDRD formula (59 vs 57%). For both equations, receiver operating characteristic curves analysis showed only a marginal gain in GFR prediction. CONCLUSION: Our data do not support the use of a cimetidine-based strategy for the evaluation of renal graft function in the clinic, particularly when the GFR is estimated by the MDRD equation.

Efficacy and safety of de novo or early everolimus with low cyclosporine in deceased-donor kidney transplant recipients at specified risk of delayed graft function: 12-month results of a randomized, multicenter trial.

Immediate or early use of proliferation signal inhibitor (PSI)/mammalian target of rapamycin (mTOR) inhibitor therapy can avoid high exposure to calcineurin inhibitors but concerns exist relating to the risk of delayed graft function (DGF) and impaired wound healing with the mTOR sirolimus. CALLISTO was a 12-month, prospective, multicenter, open-label study. Deceased-donor kidney transplant patients at protocol-specified risk of DGF were randomized to start everolimus on day 1 (immediate everolimus, IE; n = 65) or week 5 (delayed everolimus, DE; n = 74). Incidence of the primary endpoint (biopsy-proven acute rejection, BPAR; graft loss, death, DGF, wound healing complications related to transplant surgery or loss to follow-up) was 64.6% and 66.2% in the IE and DE groups, respectively, at month 12 (P = 0.860). The overall incidence of BPAR was 20.1%. Median estimated glomerular filtration rate was 48 ml/min/1.73 m(2) and 49 ml/min/1.73 m(2) in the IE and DE groups, respectively, at month 12. DGF and wound healing complications were similar between groups. Adverse events led to study drug discontinuation in 17 IE patients (26.2%) and 28 DE patients (37.8%) (NS). In conclusion, introduction of everolimus immediately or early posttransplant in DGF-risk patients is associated with good efficacy, renal function and safety profile. There seems no benefit in delaying initiation of everolimus.

Daclizumab versus antithymocyte globulin in high-immunological-risk renal transplant recipients.

Nondepleting anti-CD25 monoclonal antibodies (daclizumab) and depleting polyclonal antithymocyte globulin (Thymoglobulin) both prevent acute rejection, but these therapies have not been directly compared in a high-risk, HLA-sensitized renal transplant population. We randomly assigned 227 patients, who were about to receive a kidney graft from a deceased donor, to either Thymoglobulin or daclizumab if they met one of the following risk factors: current panel reactive antibodies (PRA) >30%; peak PRA >50%; loss of a first kidney graft from rejection within 2 yr of transplantation; or two or three previous grafts. Maintenance immunosuppression comprised tacrolimus, mycophenolate mofetil, and steroids. Compared with the daclizumab group, patients treated with Thymoglobulin had a lower incidence of both biopsy-proven acute rejection (15.0% versus 27.2%; P = 0.016) and steroid-resistant rejection (2.7% versus 14.9%; P = 0.002) at one year. One-year graft and patient survival rates were similar between the two groups. In a comparison of rejectors and nonrejectors, overall graft survival was significantly higher in the rejection-free group (87.2% versus 75.0%; P = 0.037). In conclusion, among high-immunological-risk renal transplant recipients, Thymoglobulin is superior to daclizumab for the prevention of biopsy-proven acute rejection, but there is no significant benefit to one-year graft or patient survival.

The Oxford classification of IgA nephropathy: pathology definitions, correlations, and reproducibility.

Pathological classifications in current use for the assessment of glomerular disease have been typically opinion-based and built on the expert assumptions of renal pathologists about lesions historically thought to be relevant to prognosis. Here we develop a unique approach for the pathological classification of a glomerular disease, IgA nephropathy, in which renal pathologists first undertook extensive iterative work to define pathologic variables with acceptable inter-observer reproducibility. Where groups of such features closely correlated, variables were further selected on the basis of least susceptibility to sampling error and ease of scoring in routine practice. This process identified six pathologic variables that could then be used to interrogate prognostic significance independent of the clinical data in IgA nephropathy (described in the accompanying article). These variables were (1) mesangial cellularity score; percentage of glomeruli showing (2) segmental sclerosis, (3) endocapillary hypercellularity, or (4) cellular/fibrocellular crescents; (5) percentage of interstitial fibrosis/tubular atrophy; and finally (6) arteriosclerosis score. Results for interobserver reproducibility of individual pathological features are likely applicable to other glomerulonephritides, but it is not known if the correlations between variables depend on the specific type of glomerular pathobiology. Variables identified in this study withstood rigorous pathology review and statistical testing and we recommend that they become a necessary part of pathology reports for IgA nephropathy. Our methodology, translating a strong evidence-based dataset into a working format, is a model for developing classifications of other types of renal disease.

The Oxford classification of IgA nephropathy: rationale, clinicopathological correlations, and classification.

IgA nephropathy is the most common glomerular disease worldwide, yet there is no international consensus for its pathological or clinical classification. Here a new classification for IgA nephropathy is presented by an international consensus working group. The goal of this new system was to identify specific pathological features that more accurately predict risk of progression of renal disease in IgA nephropathy, thus enabling both clinicians and pathologists to improve individual patient prognostication. In a retrospective analysis, sequential clinical data were obtained on 265 adults and children with IgA nephropathy who were followed for a median of 5 years. Renal biopsies from all patients were scored by pathologists blinded to the clinical data for pathological variables identified as reproducible by an iterative process. Four of these variables: (1) the mesangial hypercellularity score, (2) segmental glomerulosclerosis, (3) endocapillary hypercellularity, and (4) tubular atrophy/interstitial fibrosis were subsequently shown to have independent value in predicting renal outcome. These specific pathological features withstood rigorous statistical analysis even after taking into account all clinical indicators available at the time of biopsy as well as during follow-up. The features have prognostic significance and we recommended they be taken into account for predicting outcome independent of the clinical features both at the time of presentation and during follow-up. The value of crescents was not addressed due to their low prevalence in the enrolled cohort.

IL5RA and TNFRSF6B gene variants are associated with sporadic IgA nephropathy.

Familial clustering and genome-wide linkage scans strongly support a genetic susceptibility to familial IgA nephropathy (IgAN), but genetic factors that predispose to sporadic IgAN are unknown. A high-throughput single nucleotide polymorphism (SNP) association study was conducted using a customized Illumina BeadChip in 732 white patients with biopsy-proven IgAN and 503 control subjects from Canada, France, and Finland. Approximately 93% of 1536 SNPs on the array were tag SNPs from Phase I+II of the HapMap with a minor allele frequency > or =5%, designed to capture the common variants of genes within the critical interval of IGAN1 on chromosome 6q22 and 69 biologic candidate genes for IgAN. SNPs of suggestive or significant association were identified by using logistic regression to adjust for age, gender, study site, and population stratification. Despite using a dense marker set that covered an average interval of 6.5 kb between SNPs, there was no strong and consistent association signal within the IGAN1 critical interval. Among the biologic candidate genes examined, two significant association signals were found at IL5RA and TNFRSF6B, the latter being particularly interesting because this gene encodes a decoy receptor for a TNF family ligand that causes IgAN in mice when overexpressed. Pending replication, these data suggest that variants of IL5RA and TNFRSF6B may predispose to sporadic IgAN.

Antithymocyte globulin (ATG) induction therapy and disease recurrence in renal transplant recipients with primary IgA nephropathy.

Recurrence of primary IgA nephropathy after renal transplantation is clearly a time-dependent event, justifying the use of Kaplan-Meier and Cox regression analyses to sort the significant risk factors. In this retrospective study, we focused on the potential role of induction immunosuppressive therapy. We studied 116 renal transplantation (84 males, 112 cadaveric donors, 95 first grafts, mean age at Tx=46.1 years) who received, as induction, antithymocyte globulin (ATG) in 29, anti-CD25 in 35, and none in 52, associated with different maintenance therapy overtime. The 10-year cumulative recurrence rate was overall 36%, but only 9% after ATG induction when compared with 41% without induction (P=0.001). Multivariate Cox regression confirmed that ATG was protective with a 80% reduction in relative risk (P=0.01). In conclusion, this important finding needs to be confirmed in a prospective trial and if so will have major implication.