Article

Clinical and Histopathologic Characteristics Associated with Renal Outcomes in Lupus Nephritis

Emilie C. Rijnink,* Y.K. Onno Teng,† Suzanne Wilhelmus,* Mathilde Almekinders,* Ron Wolterbeek,‡ Karlien Cransberg,§ Jan A. Bruijn,* and Ingeborg M. Bajema*

Abstract Background and objectives The prognostic significance of histopathologic (sub)classes in the current classification *Departments of of lupus nephritis (LN) is controversial. We analyzed clinical and histopathologic predictors of renal outcome in Pathology, fi † LN outside the framework of the classi cation. Nephrology, and ‡Medical Statistics and Design, setting, participants, & measurements Variables (50 histopathologic and ten clinical) were tested in mixed, Bioinformatics, Leiden linear,andCoxregressionmodels for theirassociationwith renal flare,ESRD, andeGFR during follow-up (1,5, and University Medical – Center, Leiden, The 10 years) in 105 patients with LN who underwent biopsy from 1987 to 2011. The Cockcroft Gault (normalized to a Netherlands; and body surface area of 1.73 m2) and Schwartz formulas were used to calculate eGFR for adults and children, §Department of respectively. Pediatric Nephrology, Erasmus University Medical Center– Results During median follow-up of 9.9 years (25th–75th percentile, 5.9–13.8), 47 patients experienced a renal fl fl fi Sophia Children’s are and 21 progressed to ESRD. Renal are was predicted by brinoid necrosis (hazard ratio [HR], 1.04 per %; Hospital, Rotterdam, 95% confidence interval [95% CI], 1.00 to 1.07) and nonwhite race (HR, 2.23; 95% CI, 1.23 to 4.04). ESRD was The Netherlands predicted by fibrinoid necrosis (HR, 1.08 per %; 95% CI, 1.02 to 1.13), fibrous crescents (HR, 1.09 per %; 95% CI, 1.02 to 1.17), interstitial fibrosis/tubular atrophy (IF/TA) $25% (HR, 3.89; 95% CI, 1.25 to 12.14), eGFR at Correspondence: baseline (HR, 0.98 per ml/min per 1.73 m2; 95% CI, 0.97 to 1.00), and nonwhite race (HR, 7.16; 95% CI, 2.34 to Emilie C. Rijnink, Leiden University 21.91). A higher mean eGFR during follow-up was associated with normal glomeruli (+0.2 ml/min per 1.73 m2 fi Medical Center per %; 95% CI, 0.1 to 0.4). Like ESRD, a lower eGFR during follow-up was associated with brous crescents, (LUMC), Department IF/TA$25%, and nonwhite race, as well as with cellular/fibrocellular crescents (20.4 ml/min per 1.73 m2 per %; of Pathology, L1-Q, PO 95% CI, 20.6 to 20.2) and age (20.8 ml/min per 1.73 m2 per year; 95% CI, 21.2 to 20.4). Box 9600, P0-107, 2300 RC Leiden, The fi Netherlands. Email: Conclusion The LN classi cation should include an index of evidence-based prognosticators. Awaiting validation [email protected] of a formal index, we suggest that at least fibrinoid necrosis, fibrous crescents, and IF/TA warrant explicit independent scoring to assess the risk of progressive renal dysfunction in conjunction with clinical findings. Clin J Am Soc Nephrol 12: 734–743, 2017. doi: https://doi.org/10.2215/CJN.10601016

Introduction results may be due to the grouping of a wide variety of The disease manifestations and outcomes in lupus prognostically, pathogenically, and chronically different nephritis (LN) are heterogeneous, but 10%–30% of glomerular lesions in broad classes, thereby assuming patients progress to ESRD within 15 years (1,2). The that the prognosis of individuals within classes is equal prognosis can usually be improved by immunosup- regardless of the type of lesions. pression; although, there are severe and sometimes A revision of the ISN/RPS classification is called for lethal adverse effects (3). There is a constant need for (19,20). An evidence-based approach, similar to the refined and novel indicators to help clinicians pre- Oxford classification of IgA nephropathy, would be dict outcomes and determine when intensive im- the resolution for a future classification (21,22). In this munosuppression should be initiated for individual study, we aimed to identify evidence-based clinical patients with LN. and histopathologic predictors of renal outcome in LN Currently, clinical guidelines for LN (4–6) reserve outside the framework of the ISN/RPS classification. intensive immunosuppression primarily for patients with class III/IV (6V) LN according to the Interna- tional Society of Nephrology/Renal Pathology Society Materials and Methods (ISN/RPS) classification (7). Although the ISN/RPS We collected a cohort of patients, who underwent classification is useful in terms of standardization and biopsy from 1987 to 2011, with biopsy-confirmed LN reproducibility of diagnosis (8–10), studies concerning from the pathology archives at the Leiden University the power of this classification in predicting disease out- Medical Center (LUMC). Inclusion criteria were: patients come reported conflicting results (9,11–18). Conflicting with a first renal biopsy available for re-evaluation

734 Copyright © 2017 by the American Society of Nephrology www.cjasn.org Vol 12 May, 2017 Clin J Am Soc Nephrol 12: 734–743, May, 2017 Predictors of Renal Outcome in Lupus Nephritis, Rijnink et al. 735

$ fi $ with 5 scorable glomeruli, ful lling 4oftherevised the time of biopsy (age0), proteinuria at the time of biopsy, American College of Rheumatology (23,24) or Systemic erythrocyturia at the time of biopsy, MAP at the time of fi Lupus International Collaborating Clinics (25) classi ca- biopsy (MAP0), induction immunosuppression, and decade tion criteria for SLE, and with clinical follow-up at the during which the patient underwent biopsy. LUMC, Bronovo hospital (The Hague, The Netherlands), Renal Flare and ESRD. Time to first LN flare was cal- or Erasmus Medical Center (Rotterdam, The Netherlands). culated for patients who achieved (partial) remission from In accordance with the ethics committee guidelines at the the date of biopsy until the date of flare for patients who LUMC, all patient data were coded and kept anonymous. reached this endpoint; the remaining patients were censored Biopsy specimens were processed for light and immuno- at the last follow-up or at the time of ESRD. Time to ESRD fluorescence microscopy according to standard techniques was calculated analogously. Patients who reached ESRD in our center, including hematoxylin and eosin, periodic before 10 years’ follow-up were regarded as having eGFR=0 acid–Schiff, and methenamine-silver staining. Immunofluo- ml/min per 1.73 m2 at the remaining time points. Multivari- rescence reports were originally prepared by four experi- able Cox proportional-hazards models included the pre- enced nephropathologists who consistently scored specified variables and were simplified by stepwise removal immunofluorescence intensity on a 0–3+ scale. of the least significant variables. eGFR During Follow-Up. The extent by which variables Histopathology Definitions and Scoring were associated with irreversible nephron loss was in- Definitions of histopathologic lesions are shown in vestigated by modeling eGFR during follow-up. The fi Supplemental Material 1. Slides were scored by an expe- prespeci ed variables were tested for their potential to rienced nephropathologist (I.M.B.). All glomerular vari- predict a change in the intercept of the adjusted average ables were determined for each scorable glomerulus level of decline in multivariable random intercept/slope fi separately and tubulointerstitial parameters were scored linear mixed-effects models, which were simpli ed by fi categorically (Supplemental Material 1). We treated glo- removing the least signi cant variables (Wald test) and fi merular parameters as continuous variables and expressed comparing the goodness of t of nested models (maximum them as the percentage involved of all scorable glomeruli. likelihood ratio test). We considered 50 histopathologic variables (Figure 1). To Progressive eGFR Decline. To investigate progressive reduce the number of candidate variables, we excluded eGFR decline that did not necessarily result in ESRD and/ fl lesions with low prevalence (occurring in #5 patients) and or renal are, variables were analyzed in association with included only one of two strongly correlated variables progressive eGFR decline over 1, 5, and 10 years relative to (Pearson’s r/Spearman’srho.0.8). The decision on its linear prediction based upon eGFR at the time of biopsy which of the correlated variables to be included was on (eGFR0). 6 the basis of relevance and ease of scoring. Normally distributed data were expressed as mean SD. Non-normally distributed data were expressed as median (25th–75th percentile). Correlations between clinical and Clinical Dataset histopathologic variables were assessed using Pearson and The following clinical parameters were recorded for each Spearman tests, as appropriate. Given the chance of false patient at the time of biopsy: age, sex, race, mean arterial positives by multiple correlations of histopathologic vari- pressure (MAP; diastolic BP + 1/3 pulse pressure), anti- ables, Bonferroni correction was performed (Supplemental hypertensive medication, previous immunosuppression, Material 3). All other P values were two-tailed and consid- induction immunosuppression, time since SLE diagnosis, ered significant at P,0.05. All analyses were performed eGFR, 24-hour proteinuria, erythrocyturia, and the pres- using SPSS 23.0 (IBM, Armonk, NY). ence of antinuclear, antidouble-stranded DNA, and anti- phospholipid antibodies. The Cockcroft–Gault (normalized 2 to a body surface area of 1.73 m [26]) and Schwartz formulas Results were used to calculate eGFR for adults and children, respec- We retrieved 293 reports of patients with LN from the tively (27–29). The eGFR and 24-hour proteinuria were 6 pathology archives at the LUMC. Of these, 134 patients registered at 1, 5, and 10 years ( 0.5 year) and at the last were not followed at any of the specified centers, and 54 did follow-up. Clinical data were studied throughout follow- fl not have a retrievable renal biopsy specimen or their biopsy up for the occurrence of renal are and/or ESRD. specimen was of insufficient quality. Thus, 105 patients were included. Baseline clinical and laboratory findings Brief Study Outcomes and Statistical Methods are summarized in Table 1 and histopathologic findings in A complete outline of this section is given in Supple- Table 2. A complete overview of histopathologic findings mental Material 2. Outcomes were studied in two settings: and assessment of scorable glomeruli are found in Sup- (1) the complete cohort of patients with all observed LN plemental Material 4. The histopathology dataset (Figure classes who received various therapies and (2) a subset of 1) was reduced from 32 to 27 glomerular and 18 to 9 patients with class III/IV (6V) LN who received induction tubulointerstitial variables by excluding lesions occurring immunosuppression including cyclophosphamide (CYC), in #5 patients, excluding one of two strongly correlated mycophenolate mofetil (MMF), or azathioprine (AZA). Pre- variables, and combining interstitial fibrosis and tubular specified variables for multivariable analyses were: variables atrophy (IF/TA; see Supplemental Material 3). Correla- from the reduced histopathology dataset; interaction terms of tions between histopathologic variables and MAP0, these with race, age, and induction immunosuppression; and eGFR0, and proteinuria at the time of biopsy are shown the clinical variables sex, race, time since SLE diagnosis, age at in Supplemental Material 5. 736 Clinical Journal of the American Society of Nephrology

Figure 1. | Histopathologic variables that were assessed. For definitions of histopathologic lesions, see Supplemental Material 1. Percentages represent the proportion of involved scorable glomeruli. Crescent score: a multiplication factor of 1 was used for segmental crescents, and 2 for circumferential crescents. *Excluded from analyses because of low prevalence (#5 patients). †Excluded from analyses because the variable was strongly correlated with another variable (r/rho.0.8). ‡Interstitial fibrosis and tubular atrophy were combined to form the composite variable “IF/TA” (interstitial fibrosis/tubular atrophy; whichever was the higher value). +/2, scored as either present or absent.

Treatment and Outcome at the time of biopsy, 99 achieved (partial) remission; of The median follow-up was 9.9 years (25th–75th percen- these, 47 experienced a renal flare during follow-up. Fifteen tile, 5.9–13.8). Induction immunosuppression was given to of the patients who experienced a renal flare eventually 102 patients (Table 1). Patients who underwent biopsy developed ESRD. In addition to the five patients with before 2000 received significantly more frequently AZA ESRD at the time of biopsy, 16 patients progressed to ESRD and less often CYC or MMF than patients who underwent and did not regain renal function (Figure 2). Five patients biopsy after 2000 (all P,0.001). Five patients required died during follow-up due to renal failure (n=1), infection dialysis at the time of renal biopsy and did not regain renal (n=2), cardiovascular disease (n=1), and trauma (n=1). A function during follow-up. Of 100 patients without ESRD comparison between patients who underwent biopsy Clin J Am Soc Nephrol 12: 734–743, May, 2017 Predictors of Renal Outcome in Lupus Nephritis, Rijnink et al. 737

Table 1. Clinical characteristics of 105 patients with lupus nephritis at the time of renal biopsy

Characteristic All Patients (n=105)

Decade of renal biopsy, n (%) 1980–1989 7(7) 1990–1999 36 (34) 2000–2009 56 (53) 2010–2011 6(6) Age, yr Mean6SD 29.8613.2 ,18 yr, n (%) 22 (21) Females, n (%) 83 (79) Race, n (%) White 68 (65) Asian 24 (23) Afro-Caribbean 13 (12) Previous diagnosis of SLE, n (%) 77 (73) Years since SLE diagnosis, median (25th–75th percentile) 4.2 (1.1–7.9) Diagnosis of SLE at the time of biopsy, n (%) 28 (27) BMI, kg/m2 Mean6SD 22.464.4 Diastolic BP $90 mmHg, n (%) (n=101) 31 (31) MAP (mmHg) Mean6SD 97617 Taking antihypertensive medication, n (%) (n=103) 34 (33) Treated with RAS blockade, n (%) (n=103) 19 (18) Induction immunosuppression, n (%) No immunosuppression 3(3)a CS alone 4(4)b CS + CYC NIH 26 (25) CS + CYC EuroLupus 27 (26) CS + MMF 14 (13) CS + AZA 31 (30) 2 eGFR0, ml/min per 1.73 m Mean6SD 76.5636.2 CKD stage, n (%) 1 36 (34) 2 34 (32) 3 24 (23) 4 9(9) 5 2(2) Proteinuria0,g/24h Median (25th–75th percentile) 2.48 (1.25–5.00) Erythrocyturia, n 2/+/++/+++ 5/22/22/56 Previous immunosuppression, n (%) 19 (18) ANA, n (%) 104 (99) Anti-dsDNA, n (%) (n=101) 77 (76) Antiphospholipid antibodies, n (%) (n=57) 29 (51)

The numberofpatients with validregistrations isindicated ifdata were missingfor some patients. BMI,bodymass index;MAP,mean arterial pressure; RAS, renin-angiotensin system; CS, corticosteroids; CYC, cyclophosphamide; NIH, National Institutes of Health; 2 MMF, mycophenolate mofetil; AZA, azathioprine; Proteinuria0, proteinuria at time of biopsy; /+/++/+++, erythrocyturia score ([2]0–18 erythrocytes/mL; [+] 19–25 erythrocytes/mL; [++] 26–40 erythrocytes/mL; [+++] .40 erythrocytes/mL); ANA, anti-nuclear – antibody; anti-dsDNA, anti double stranded DNA antibody; eGFR0, eGFR at the time of biopsy. aPatients (n=3) with class III, IV, and III+V lupus nephritis. bPatients with class III/IV (n=2) and class V (n=2) lupus nephritis.

before and after 2000 revealed no difference in renal Tables 3 and 4). Below, parameter estimates refer to the survival (P=0.34) and renal flare rate (P=0.66). complete cohort. Renal Flare and ESRD. Nonwhite race (hazard ratio Predictors of Renal Outcome [HR], 2.23; 95% confidence interval [95% CI], 1.23 to 4.04) Predictors of renal outcome were similar for the com- and fibrinoid necrosis (HR, 1.04 for each percent of glomeruli; plete cohort and the subset (Supplemental Material 6, 95% CI, 1.00 to 1.07) independently predicted renal flare 738 Clinical Journal of the American Society of Nephrology

Table 2. Distribution of selected histopathologic findings in 105 patients with lupus nephritis

Variable All Patients (n=105)

Scorable glomeruli, n Median (25th–75th percentile) 13 (10–19) ISN/RPS class, n (%) I 1(1) II 3(3) III 24 (23) IV 60 (57) III/IV + V 12 (11) V 5(5) Normal glomeruli, n (%) Absent 47 (45) 1%–24% of glomeruli 37 (35) 25%–49% of glomeruli 16 (15) $50% of glomeruli 5(5) Global sclerosis, n (%) Absent 71 (68) 1%–24% of glomeruli 21 (20) 25%–49% of glomeruli 10 (10) $50% of glomeruli 3(3) Mesangial hypercellularity, n (%) Absent 22 (21) 1%–24% of glomeruli 38 (36) 25%–49% of glomeruli 34 (32) $50% of glomeruli 11 (10) Endocapillary hypercellularity, n (%) Absent 12 (11) 1%–24% of glomeruli 26 (25) 25%–49% of glomeruli 17 (16) $50% of glomeruli 50 (48) Crescents, n (%) Absent 38 (36) 1%–24% of glomeruli 30 (29) 25%–49% of glomeruli 24 (23) $50% of glomeruli 13 (12) Interstitial infiltration, n (%) Absent 56 (53) 1%–24% of glomeruli 37 (35) 25%–49% of glomeruli 4(4) $50% of glomeruli 8(8) IF/TA, n (%) Absent 67 (64) 1%–24% of glomeruli 26 (25) 25%–49% of glomeruli 8(8) $50% of glomeruli 4(4)

ISN/RPS, International Society of Nephrology/Renal Pathology Society; IF/TA, interstitial fibrosis or tubular atrophy.

(Table 3). The following variables independently predicted glomeruli (95% CI, 20.6 to 20.2), as did fibrous crescents ESRD (Table 3): nonwhite race (HR, 7.16; 95% CI, 2.34 to (21.4 ml/min per 1.73 m2 per % glomeruli; 95% CI, 22.4 2 2 $ 2 21.91), eGFR0 (HR, 0.98 for each ml/min per 1.73 m ;95%CI, to 0.5) and the presence of IF/TA 25% ( 40.5 ml/min 0.97 to 1.00), fibrous crescents (HR, 1.09 for each percent of per 1.73 m2; 95% CI, 256.2 to 224.8). Conversely, each glomeruli; 95% CI, 1.02 to 1.17), fibrinoid necrosis (HR, 1.08 percent of normal glomeruli, including glomeruli with 1–3 for each percent of glomeruli; 95% CI, 1.02 to 1.13), and the leukocytes, independently predicted an overall higher presence of IF/TA$25% (HR, 3.89; 95% CI, 1.25 to 12.14). eGFR (+0.27 ml/min per 1.73 m2 per % glomeruli; 95% CI, eGFR During Follow-Up. The adjusted mean eGFR at the 0.1 to 0.4). Clinically, nonwhite race and age0 independently time of renal biopsy was 116.5 ml/min per 1.73 m2,withan predicted an overall lower eGFR (211.4 ml/min per 1.73 m2; average change of 20.7 ml/min per 1.73 m2 per year (Table 4). 95% CI, 221.9 to 20.8; and 20.7 ml/min per 1.73 m2 per Cellular/fibrocellular crescents independently predicted an year; 95% CI, 21.2 to 20.4, respectively). overall lower eGFR (i.e., lower adjusted mean eGFR at baseline Progressive eGFR Decline. Briefly, a decline of eGFR over and during follow-up) of 20.4 ml/min per 1.73 m2 per % 1 and 5 years was independently predicted by nonwhite race, Clin J Am Soc Nephrol 12: 734–743, May, 2017 Predictors of Renal Outcome in Lupus Nephritis, Rijnink et al. 739

Figure 2. | Probabilities of renal survival and renal flare among patients in the cohort. Time to ESRD (A, n=105) and time to first renal flare (B, n=99) are depicted according to the Kaplan–Meier method. (A) During follow-up, 21 patients progressed to ESRD. The probability of renal survival was 93% at 1 year, 90% at 5 years, 85% at 10 years, and 71% at 20 years of follow-up. (B) Patients were only considered who achieved (partial) remission after renal biopsy and were not censored because they already reached ESRD. During follow-up, 47 patients experienced a renal flare. The probability of renal flare was 8% at 1 year, 35% at 5 years, and 48% at 10 years.

fi fi $ age0, brinoid necrosis, brous crescents, and IF/TA 25%. patients treated with AZA within the class III/IV subset Contrastingly, wire loops and endocapillary lymphocytes (Supplemental Material 7). Spikes/vacuoles and tubular were associated with eGFR recovery over 10 years’ follow-up reabsorption droplets were associated with a lower eGFR (Supplemental Material 6). during follow-up in patients with Afro-Caribbean race compared with other races (Supplemental Material 7). fi Influence of Therapy, Race, and Age on the Predictive Values None of the prespeci ed clinical variables were corre- of Histopathologic Variables lated both with spikes/vacuoles or tubular reabsorption In the complete cohort, cytotoxic immunosuppression droplets and race. Age0 showed no interactions with and/or angiotensin-converting enzyme inhibition were histopathologic variables for the different outcomes (Sup- not associated with any of the renal outcomes (Supple- plemental Material 7). mental Material 2). Of the histopathologic variables, only segmental/global endocapillary hypercellularity (P=0.03) Immunofluorescence in Relation to Outcome and cellular crescents (P=0.05) were associated with The intensities of the individual immunoglobulins cytotoxic immunosuppression (CYC, MMF, or AZA). (IgA,IgG,andIgM)andCfactors(C3andC1q)were Therapy showed no interactions with histopathologic not associated with ESRD, renal flare, or eGFR during variables for the different outcomes, with the exception of follow-up (data not shown); neither were different immu- global glomerulosclerosis with ESRD (HR, 1.03 for each nofluorescence patterns, including ,1+IgGandC1qor percent glomeruli; 95% CI, 1.00 to 1.06; P=0.01) only in the full house pattern.

Table 3. Multivariable prediction models for renal flare and ESRD

ISN/RPS Class I–V ISN/RPS Class III/IV (6V)a (n=105) (n=91) Model HR (95% CI) P Value HR (95% CI) P Value

Renal flare (n=99) Nonwhite 2.23 (1.23 to 4.04) 0.01 2.08 (1.09 to 3.98) 0.03 % Fibrinoid necrosis (glomerular) 1.04 (1.00 to 1.07) 0.04 1.04 (1.00 to 1.08) 0.04 ESRD (n=105) Nonwhite 7.16 (2.34 to 21.91) 0.001 9.12 (2.85 to 29.22) ,0.001 Age0, yr 1.02 (0.99 to 1.06) 0.18 1.02 (0.99 to 1.06) 0.23 2 , eGFR0, mL/min per 1.73 m 0.98 (0.97 to 1.00) 0.05 0.99 (0.97 to 1.00) 0.12 % Fibrinoid necrosis (glomerular) 1.08 (1.02 to 1.13) 0.004 1.07 (1.02 to 1.13) 0.01 % Fibrous crescents 1.09 (1.02 to 1.17) 0.02 1.10 (1.02 to 1.19) 0.01 IF/TA$25% 3.89 (1.25 to 12.14) 0.02 4.53 (1.40 to 14.73) 0.01

fi ISN/RPS, International Society of Nephrology/Renal Pathology Society; HR, hazard ratio; 95% CI, 95% con dence interval; Age0,ageat fi time of biopsy; eGFR0, eGFR at the time of renal biopsy; IF/TA, interstitial brosis/tubular atrophy. aPatients with class III/IV (6V) lupus nephritis who received induction immunosuppressive treatment with cytotoxic drugs were analyzed separately from the complete cohort. 740 Clinical Journal of the American Society of Nephrology

Table 4. Multivariable prediction model for the course of eGFR during follow-upa

ISN/RPS Class I–V ISN/RPS Class III/IV (n=105) (6V)b (n=91) Model P P b (95% CI) b (95% CI) Value Value

Intercept 116.5 (100.1 to 132.8) ,0.001 116.4 (98.9 to 133.9) ,0.001 Time, yr 20.7 (21.5 to 0.0) 0.06 20.6 (21.4 to 0.2) 0.13 Baseline predictors Nonwhite 211.4 (221.9 to 20.8) 0.04 213.5 (225.2 to 21.7) 0.03 2 2 2 , 2 2 2 , Age0,yr 0.8 ( 1.2 to 0.4) 0.001 0.8 ( 1.2 to 0.4) 0.001 Normal glomeruli/minimal leukocyte 0.2 (0.1 to 0.4) 0.01 0.2 (0.0 to 0.5) 0.03 influx, % Cellular/fibrocellular crescents, % 20.4 (20.6 to 20.2) 0.001 20.4 (20.6 to 20.1) 0.003 Fibrous crescents, % 21.4 (22.4 to 20.5) 0.004 21.6 (22.6 to 20.5) 0.004 IF/TA$25% 240.5 (256.2 to 224.8) ,0.001 241.4 (258.3 to 224.4) ,0.001

b 2 t t b 3t Z Z indicates eGFR in ml/min per 1.73 m .eGFRattime is given by the following: eGFR( ) = intercept + Time + ,where is the value b 3 b 3 given by the baseline predictors of the patient: Z = Age0 Age0[y] + Normal glomeruli/minimal leukocyte influx Normal glomeruli/minimal fl b 3 fi b 3 fi b leukocyte in ux[%] + cellular/fibrocellular crescents cellular/ brocellular crescents[%] + fibrous crescents brous crescents[%] + nonwhite b $ (if nonwhite) + IF/TA$25% (if IF/TA 25%). ISN/RPS, International Society of Nephrology/Renal Pathology Society; 95% CI, 95% fi fi con dence interval; Age0, age at time of biopsy; IF/TA, interstitial brosis/tubular atrophy. aMixed-model analysis. bPatients with class III/IV (6V) lupus nephritis who received induction immunosuppression with cytotoxic drugs were analyzed separately from the complete cohort.

ISN/RPS Classes in Relation to Outcome indicates that the relatively unaffected part of the kidney is ISN/RPS classes were not significantly associated with vital in determining renal function. This notion is well known overall renal survival (P=0.72) and renal flare (P=0.29). LN in the setting of ANCA-associated GN, where biopsy classes were significantly associated with eGFR during specimens in which $50% of glomeruli are normal using follow-up (P,0.05), with the lowest eGFR in class IV-S LN. identical definitions have been incorporated in a well For detailed results, see Supplemental Material 8. validated “focal class” in the classification (30–35). On the basis of our results, glomeruli that are normal by light microscopy may similarly transcend the LN classes and Discussion warrant incorporation into a separate index. Controversies surrounding the prognostic significance Only a limited number of active glomerular lesions had of histopathologic (sub)classes in the classification of LN adverse prognostic value. Of the endocapillary lesions, indicate that the prognosticators should be restructured wire loops and endocapillary lymphocytes were associ- from scratch (19,20). Without preconceptions, we ana- ated with eGFR recovery rather than decline over 10 years’ lyzed clinical and histopathologic predictors of renal follow-up (Supplemental Material 6), suggesting that the outcome in 105 patients with class I–V LN, including a treatment of active endocapillary lesions was successful subset of 91 patients with class III/IV (6V) LN treated and damage was largely reversible for most patients. This relatively uniformly with cytotoxic immunosuppression. result reflects the suggestion of the Oxford study on IgA Essentially, our analysis of the different outcomes in the nephropathy that endocapillary hypercellularity is a lesion complete cohort and its subset revealed two categories of more responsive to immunosuppression given the lack of clinical and histopathologic predictors: (1) variables pre- its association with renal function decline among patients dictive of the level of eGFR during follow-up and (2) who received immunosuppression (22). In contrast with variables predictive of renal flare, progressive eGFR active endocapillary lesions, the association of cellular/ decline, and ultimately ESRD. The variables that emerged fibrocellular crescents with a lower eGFR during follow-up as independent predictors in the complete cohort were suggests active extracapillary lesions may result in irrevers- consistent with the predictors in the class III/IV (6V) LN ible damage. Yet, like active endocapillary lesions, active subset. Here, we discuss the clinicopathologic predictors extracapillary lesions were not associated with progressive of renal outcome as identified among patients with class eGFR decline. The prognostic significance of extracapillary I–VLN. lesions also implies a treatment effect, but more in terms of In our study, the percentage of normal glomeruli with ,4 halting the progression. In the current classification of LN, leukocytes, in the absence of other abnormalities, was the active endocapillary and extracapillary lesions contribute only independent histopathologic predictor associated with a equally to the assignment of class III/IV LN. Our findings higher eGFR during follow-up. The prognostic significance of indicate that more weight should be given to extracapillary glomeruli that are normal by light microscopy most likely lesions. Clin J Am Soc Nephrol 12: 734–743, May, 2017 Predictors of Renal Outcome in Lupus Nephritis, Rijnink et al. 741

In contrast with other active glomerular lesions, fibrinoid general provides circumstantial evidence that AZA necrosis was not associated with eGFR0,butratherwithrenal should not be recommended as induction therapy in flare, progressive eGFR decline, and ESRD. Interestingly, case of chronic lesions. fibrinoid necrosis was correlated with segmental, but not In conclusion, our results show that although ISN/RPS global, endocapillary hypercellularity. This finding is consis- classes were poorly associated with the clinically relevant tent with the notion that global and segmental lesions outcomes, prognostication in LN may benefitfromthespecific represent distinct entities in class IV LN (13,14,36), and that assessment of clinical variables and lesions currently obscured segmental lesions, with emphasis on fibrinoid necrosis, may in the classification. Normal glomeruli, cellular/fibrocellular have a different immunopathogenesis than global lesions (13). crescents, fibrous crescents, and IF/TA were potent predictors Apart from fibrinoid necrosis, chronic glomerular le- of eGFR during follow-up. Importantly, particularly active sions were generally better predictors of eGFR and pro- endocapillary lesions were likely responsive to immunosup- gressive eGFR decline than active lesions. Fibrous pressionbecausetheywerenotassociatedwithrenalfunction crescents were independently associated with lower deterioration. Contrastingly, fibrinoid necrosis, fibrous cres- eGFR during follow-up, progressive eGFR decline, and cents, and IF/TA predicted progressive renal dysfunction ESRD. Correspondingly, it has been demonstrated that the even in the uniformly treated subset, implying that these composite chronicity index devised by Austin et al. (37), as lesions are unlikely to benefit from immunosuppression and well as its components individually, are excellent predic- thereby correspond to the clinically most relevant category of tors of ESRD; whereas, the activity index and its compo- predictors. An evidence-based era of classifying LN is on the nents are weaker predictors (37–42). horizon, with an international effort to refine the histopath- Currently, primarily the histopathologic class on the basis ologic classification already on its way. Our results suggest of glomerular pathology determines the recommended that LN classes should be expanded with an evidence-based clinical management of LN (4–6). Our results confirm that, index, analogous to the mesangial and endocapillary hyper- in addition to glomerular variables, tubulointerstitial cellularity, segmental sclerosis and IF/TA (MEST) score in variables including IF/TA, interstitial infiltrates, tubular the Oxford classification, with special attention to defining casts, and arterial intimal fibrosis (38,39,41–44); as well as clinically important categories of predictors. Awaiting further fi clinical variables including nonwhite race, age, MAP0,and validation of a formal index, we suggest that at least brinoid fi eGFR0, are also valuable predictors of renal outcome in necrosis, brous crescents, and IF/TA warrant explicit LN (39,40,45,46). independent scoring to assess the risk of progressive renal Our study has some limitations. First, the predictors we dysfunction in conjunction with clinical findings. identified apply to patients with the spectrum of clinical and histopathologic features observedinourcohort,inwhichthe Acknowledgments biopsy specimens were scored by an experienced nephropa- Y.K.O.T. was supported by the Dutch Kidney Foundation thologist using our definitions. Indeed, a number of lesions, (KJPB12.028) and a Clinical Fellowship by The Netherlands Or- fi including microthrombi and vasculitis, were excluded from our ganization for Scienti cResearch. analyses due to a low prevalence. These lesions may well have Disclosures prognostic significance and should be evaluated in other None. cohorts. Second, we did not analyze electron microscopy, which, if at hand, is the usual complement to light and immunofluorescence microscopy to comprehensively study References LN pathology. Whereas in our study immunofluorescence 1. 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