Identification of Clinical and Histopathologic Risk Factors for Diminished Renal Function 2 Years Posttransplant

Identification of Clinical and Histopathologic Risk Factors for Diminished Renal Function 2 Years Posttransplant PETER NICKERSON,* JOHN JEFFERY,* JAMES GOUGH,t RACHEL MCKENNA,* PAUL GRIMM, MARY CHEANG, and DAVID RUSH* Departments of *Medjcj,sze, tpathologv, Pediatrics, and Cominunitv Health Services, Unil ersit% of Manitoba, Winnipeg, Manitoba, Canada. Abstract. The aim of this study was to identify early clinical and pathologic variates that independently predict diminished renal albograft function at 24 mo posttnansplant. A clinical pathologic data base was prospectively derived from 7 1 patients in whom protocol renal biopsies were performed at 1, 2, 3, 6, and I 2 mo posttransplant. The major end point was the 24-mo serum creatinine. Variates correlating independently (r2 = 0.67) with the 24-mo serum creatinine were the chronic biopsy scores (months 3 and 6), bate rejections (months 4 to 6), cycbosponin A (CsA) levels (months 1 to 2), and delayed graft function. The adjusted odds ratio (OR) and 95% confidence interval (CI) for having a serum creatininc 1 30 jtmol/l at 24 mo increased for every year the donor age increased (OR = 1.07; 95% CI, I.02 to I. 13; range, 9 to 55) or for each late rejection episode (OR = 5.9; 95% CI, I.7 to 20. 1 ), whereas a mean CsA level >300 tgfl from months I to 3 was protective (OR = 0.07; 95% CI, 0.01 to 0.43). Variates correlating independently (r = 0.53) with the change in serum crcatininc from 6 to 24 mo (Cr6_,4) were the chronic biopsy scores at months 3 and 6. The adjusted OR of the zcr6,4 rising +20 tmol/l increased for every year the donor age increased (OR = 1.09; 95% CI, 1.02 to 1. 16; range 9 to 56) or when the 6-mo chronic biopsy scone was 2 (OR = 6.6; 95% CI, 1.2 to 36.4). An estimate of the relative risk for diminished renal function at 2 yr can be assigned within 6 mo of transplant based on chronic pathology, late acute rejections, CsA levels, and donor age. (J Am Soc Nephrol 9: 482-487, 1998) One-year graft survival of renal transplants treated with cycbosponin A (CsA) is 80 to 90% ( 1,2). Beyond the first year, graft loss occurs at a steady rate due to patient death (50%) or chronic rejection (25%) (3,4). The design of clinical trials to prevent late graft loss is hindered by the need for a large number of patients and the protracted time of follow-up (5,6). Trial design and clinical patient management would be facilitated by the early assignment of a relative risk score for the development of chronic rejection and by the identification of surrogate end points of long-term graft loss. The purpose of this single-center study was to identify, in the first 6 mo posttransplant, clinical and/or histopathobogic determinants that correlate with diminished renal function at 2 yr posttransplant. Materials and Methods Since 1990, our clinical investigation unit has performed protocol renal allograft biopsies with informed consent and approval by the University Medical Ethics Committee (7,8). From August 1990 to December 1995, there were 184 adult renal allografts transplanted, of which 7 1 had protocol biopsies at 1, 2, 3. 6, and 12 mo posttransplant. Thirty-five of these patients were in a prospective pilot study. using protocol renal biopsies to determine the prevalence of subclinical Received July 14. 1997. Accepted September 22. 1997. Correspondence to Dr. Peter Nickerson. Basic Medical Sciences Building, Room 61 1. 730 William Avenue, Winnipeg, Manitoba, Canada R3E 0W6. 1046-6673/0903-0482$03.00/0 Journal of the American Society of Nephrobogy Copyright D 1998 by the American Society of Nephrology rejection (defined below). The remaining 36 patients were part of a subsequent prospective, randomized study designed to determine the benefit of treating early subclinical rejections. In both studies, patients with histologic evidence of rejection detected by protocol biopsy received treatment with a standard antirejection regimen (i.e., a tapering course of high-dose corticosteroids). The patients in these two studies were combined for analysis, because together they formed a unique group that was homogeneous with regard to clinical and histopathobogic data collection, and the immunosuppressive protocol. Living-rebated transplants were performed in 6 of 7 1 cases, and 65 of 7 1 were cadavenic grafts. There were 13 patients with type I diabetes ruellitus. Patients were excluded from enrollment for the following reasons: complete HLA match (n = 12): death in the first month (a = 7): graft failure secondary to rejection in the first month (ii = 16); refused consent (, = 26); technical difficulties (e.g., obesity, anticoagulated, anteposition of the bowel) (a = 15); early disease recurrence (n = 1 ): or enrolled in another study (a = 36). From 1990 to 1995, immunosuppression for all renal allograft recipients was a standardized triple therapy protocol. This consisted of cyclosporin A (Sandimmune; Sandoz, Basel, Switzerland) 3 mg/kg per d by intravenous infusion for 3 to 5 d, followed by oral CsA sufficient to achieve target trough levels of 250 to 350 g/l in the first 3 mo and I 50 to 200 jtg/l thereafter. CsA levels were measured in whole blood, 12 h after dosing, using the ruonoclonal TDx system. Azathioprine was given at 1 to 2 rug/kg per d, and prednisone was given at I mg/kg per d with taper. Rejection episodes, defined either on clinical grounds or by pathologic criteria, were treated with a tapering course of high-dose steroids. OKT3 was given to only 12 patients (5 rug intravenously for 7 d), four as induction therapy and eight for steroid-resistant rejection. Finally, all patients received a calcium channel blocker (i.e., diltiazem) from the time of transplant. Core renal albograft biopsies were performed in the clinical inves-

Risk Factors of Declining Renal Allograft Function 483 tigation unit, using an I 8-gauge spring-loaded gun with ultrasound guidance. Acute inflammation and chronic changes were scored according to the Banff schema (9). The chronic score was divided for analysis into a score for interstitial fibrosis plus tubular atrophy and loss (CI + CT) and a score for chronic transplant gloruerulopathy plus fibrous intimal vasculopathy (CG + CV). Two cores of tissue were obtained and evaluated by our renal pathologist, who was blinded to the clinical status of the patient. The CsA level reported at the time of a protocol biopsy was the average of the last three recorded levels. At the time of protocol biopsy, an episode of clinical rejection was diagnosed when a histologic lesion with a total acute inflammatory score 4 (i.e., consistent with a histologic diagnosis of grade I rejection by the Banff schema) was accompanied by an increase in the serum creatinine > 10% from the baseline of the preceding 2 wk. Between protocol biopsies, an episode of clinical rejection was defined by an increase in the serum creatinine > I 0% from the baseline, for which an alternative diagnosis was excluded (e.g., obstruction). Moreover, the diagnosis of rejection was confirmed by a subsequent decrease in the serum creatinine in response to an increase in steroids. or OKT3 administration. Subclinical rejection episodes were defined by an acute inflammatory score 4 without an increase in the serum creatinine > 10% from baseline. For the purposes of our analysis. we categorized rejection episodes as early if they occurred between 0 and 3 mo or late if they occurred between 4 and 6 mo posttransplant. Statistical Analyses Values reported are mean ± SEM or, where indicated, as medians and ranges. Analysis was conducted using SAS software (version 6.08) in conjunction with the Biostatistical Consulting Unit of the University of Manitoba. Testing for correlations between clinical and histologic parameters was done by Pearson correlation analysis or, where appropriate. Spearman rank correlation test. All possible subset multiple linear regression analysis was used to assess and define the relative roles of predictive variates along with their interactions. Of the 355 possible protocol biopsies, 319 (approximately 90%) were obtained: 58 at I mo, 60 at 2 ruo, 65 at 3 mo, 70 at 6 mo, and 66 at 12 mo. Moreover, of the patients missing I- or 2-mo biopsies, only 15% and 10% had evidence of chronic allograft pathology subsequently at 3 or 6 mo. respectively. Therefore, for the purpose of multiple regression analysis, missing values for chronic scores were assigned a score of 0. Backward stepwise logistic regression modeling was applied to both a cutoff for the serum creatinine of I 30 j.ruol/l at 24 mo and a change in the creatinine from 6 to 24 mo of +20 jruol/l. The comparison of subgroups used either two-tailed t tests, ANOVA, or Wilcoxon rank sum tests. Results All 7 1 patients in the analysis have reached 12 mo, whereas 62 of 7 1 are beyond 24 mo. At 6 mo posttransplant, 68 of 71 patients had a serum creatinine <250 p.molil. Graft failure due to chronic albograft ncphropathy occurred at month I 3 in one patient, whereas another patient died at month 1 3 posttransplant with a functioning graft. Only one patient in the analysis had persistent histopathobogic changes consistent with CsA toxicity (24-mo creatinine, 167 tmolil). At 12 mo posttransplant, the mean creatinine was 146 ± 9 p.molll and the mean daily protein excretion was 0.3 1 ± 0.07 g/d. For those individuals who have reached 24 mo, the mean creatininc was 149 ± 1 1 jtmolll, with a mean daily protein excretion of 0.47 ± 0.12 g/d. The prctransplant demographics for the group arc surumanized in Table I. The panel reactive antibody at the time of transplant was low in most patients (mean, 1.0 ± 0.5%; range, 0 to 35%). Total HLA matching was relatively poor (mean, 2. 1 ± 0. 1 ; range, 0 to 5 matches). The recipient and donor ages, as well as the mean cold ischcmic time, were similar to those reported by other groups ( I 0-I 2). The incidence of delayed graft function (i.e., a failure of the creatininc to decline in the first 48 h in the absence of rejection) was 20%. The clinical and histologic parameters evaluated in the first 6 mo posttransplant are summarized in Table 2. The majority (80%) of the rejection episodes occurred early (months 1 to 3). The ratio of clinical to subclinical rejections between 0 and 6 mo was approximately 2: 1. The degree of acute inflammation detected by protocol biopsies (i.e., mean acute score) progrcssively decreased from months 1 to 6. Conversely, the mean chronic biopsy score of the group was negligible in months 1 and 2, but increased at months 3 and 6 posttransplant. Correlation coefficients for the pretransplant and posttransplant variates with the serum creatininc at I 2 and 24 mo, by univariate analysis, arc shown in Table 3. Of particular note, the total chronic score at 6 ruo correlated with the 12- or 24-mo serum creatinine. Moreover, when one analyzed the interstitial fibrosis + tubular atrophy (CI + CT) scone, or the gborucrubopathy + fibrous intirual vascubopathy (CO + CV) score, both correlated equally well with the 12- or 24-mo creatinine. Indeed, the mean 6-mo CI + CT score (0.33 ± 0.09) and the CG + CV scone (0.36 ± 0.09) were not statistically different (P NS). Finally, although we report the correlation of the I 2- and 24-mo serum creatininc with the CG + CV score, the CG + CV score was solely due to the CV score in >90% of the cases. By multiple regression analysis, the variates correlating independently (r2 = 0.67) with the 24-mo serum crcatininc were the chronic biopsy scores at 3 and 6 mo, late clinical and subclinical rejection episodes, the mean of the 1 - to 2-mo CsA levels, and delayed graft function. Variates correlating mdcpcndently (r2 = 0.48) with the number of late rejection episodes were the panel reactive antibody level at the time of transplant, the cold ischcmic time, the mean of the 1 - to 3-mo CsA levels, the number of early clinical rejection episodes, and the 3-mo chronic biopsy score. For the purposes of modeling, excellent renal function was arbitrarily defined as a creatinine < 130 p.mol/l at 24 mo posttransplant. Compared to the group with excellent renal Table I. Pretransplant dcruognaphicsa PRA at transplant (%) 1.0 ± 0.5 HLA-A match 0.80 ± 0.06 HLA-B match 0.58 ± 0.07 HLA-DR match 0.65 ± 0.07 Recipient age (yr) 42.8 ± 1.4 Donor age (yr) 33.8 ± 1.9 Cold ischcruic time (ruin) 1065 ± 58 Delayed graft function 14/71 (20%) a PRA, panel reactive antibody.

484 Journal of the American Society of Nephrology Table 2. Posttranspbant clinical and histologic demographics Characteristic Month 1 2 3 6 CsA level (tgfl) 309 ± 8 283 ± 10 277 ± 8 243 ± 7 Total rejectionsb 1.38 ± 0.09 2.17 ± 0.12 2.73 ± 0.14 3.41 ± 0.19 clinical 1.04 ± 0.09 1.49 ± 0.12 1.80 ± 0.13 2.25 ± 0.18 subclinical 0.34 ± 0.06 0.68 ± 0.08 0.93 ± 0.10 1.16 ± 0.11 Acute score 3.60 ± 0.18 3.47 ± 0.21 2.40 ± 0.21 2.24 ± 0.22 Chronic score 0. 1 5 ± 0.07 0. 1 0 ± 0.05 0.39 ± 0. 1 3 0.70 ± 0.15 Creatinine (.tmo1il) 151 ± 7 141 ± 5 139 ± 6 142 ± 7 Proteinuria (pg/d) ND ND 0.39 ± 0.04 0.33 ± 0.04 a CsA, cyclosporin A; ND, not determined. I, Rejections are cumulative and expressed as the mean number that had occurred for the group up to and including the time point. Table 3. Variate correlations with the 12- and 24-mo serum crcatinincu Correlation 12-mo Creatinine (F = 71) 24-mo Creatinine (n 62) HLA (A + B) match -0.27-0.25 Donor age (yr) 0.34 0.35 Delayed graft function NS 0.27 CsA level month 1 (tgil) -0.34-0.33 CsA level month 2-0.38-0.47 CsA level month 3 MS MS CsA level month 6 MS MS Mean CsA level months I to 2-0.44-0.48 Mean CsA level months 1 to 3-0.42-0.47 Early rejection episodes NS NS Late rejection episodes 0.59 0.58 clinical rejection months 4 to 6 0.49 0.50 subclinical rejection month 6 0.38 0.36 Acute score at 3 mo NS NS Acute score at 6 mo 0.34 0.32 Chronic score at I mo NS MS Chronic score at 2 mo NS MS Chronic score at 3 mo 0.45 0.47 Chronic score at 6 mo 0.47 0.48 CI + CT at 6 mo 0.39 0.41 CG + CV at 6 mo 0.44 0.45 a All correlations shown are significant at P < 0.05. CI + CT, interstitial fibrosis plus tubular atrophy and loss; CG + CV, chronic transplant glomerulopathy plus fibrous intirual vascubopathy. Other abbreviations as in Table 2. function, patients with a creatinine 1 30 j.ruolil had older donors, an increased frequency of delayed graft function, lower CsA bevels in months 1 and 2 posttranspbant, an increased number of late rejection episodes, and an increased acute score on the 6-mo biopsy (Table 4). The adjusted odds ratio (OR) and 95% confidence interval (CI) of having a serum creatinine 1 30 moljl at 24 mo increased for every year the donor age increased (OR = 1.07; 95% CI, 1.02 to 1.13; range, 9 to 55) or foreach late rejection episode (OR = 5.9; 95% CI, 1.7 to 20.1) whereas a CsA level >300 pgil from months 1 to 3 was protective (OR = 0.07; 95% CI, 0.01 to 0.43). Indeed, for every increase in the mean 1 - to 2-mo CsA bevel of 1.0 gfl, the relative odds of having a creatininc 130.tmol/L decreased by 2.5% (OR = 0.975; 95% CI, 0.960 to 0.990) over a CsA level range of 197 to 606 p.g/l. The 24-mo serum creatininc correlated strongly with the 6-mo serum creatininc (r = 0.84; P < 0.001), and although the mean change in serum creatinine from 6- to 24-mo posttransplant (zcr6_24) was only 4.9 ± 6.6 tmol/l, three outcomes could be identified by a Cr6_24 of ±20 p.molll, values < or > 2 SEM from the mean (Table 5 and Figure 1). The variates that correlated independently (r = 0.53) with the Cr6_24 were the 3- and 6-mo chronic biopsy scores. Modeling based on the LCr6_24 found that the adjusted OR of the Cr6_24 rising +20.tmolIL increased for every year the donor age increased (OR = 1.09; 95% CI, 1.02 to 1. 16; range 9 to 56), and when the 6-mo chronic biopsy score was 2 (OR = 6.6; 95% CI, 1.2 to 36.4). Discussion Chronic rejection has been defined as a gradual deterioration in graft function (at least over a 3-mo interval, after 3 mo posttransplant) in the absence of any other disease, and requires biopsy confirmation (1 3). Previous studies have identifled risk factors for the development of chronic rejection (3,4). This single-center study identified in the first 6 mo posttransplant that chronic pathology, late rejection episodes, insufficient CsA dosing, and delayed graft function arc independent variates predictive of an elevated serum creatinine at 2 yr. The principal predictor of a subsequent decline in renal function (zcr6_24) beyond 6 mo was the acquired chronic pathology at 6ruo. Only two studies have previously documented an association between chronic allograft pathology found at protocol biopsy and subsequent allognaft function. Isoniemi et al. found that in patients with normal renal function, a 2-yr chronic biopsy score was the single most important predictor of subsequent chronic

Risk Factors of Declining Renal Ablografi Function 485 Table 4. Subgroups defined by a creatinine < I 30 or I 30 j.mobil at 24 mo posttransplant Characteristic.. < I 30 jmol/l 130 p.mol/l ( 32) (a 30) P Value Donor age (years) 29. 1 ± 2.5 39.9 ± 2.8 0.006 Delayed graft function 4/32 ( 13%) 9/30 (30%) NS CsA level month 1 (j.lgil) 333 ± 12 279 ± 10 0.001 CsA level month 2 310 ± 16 240 ± 10 0.0006 CsA level month 3 280 ± 1 1 260 ± 1 1 MS Mean CsA level months 1 to 2 321 ± 13 260 ± 8 0.0001 Mean CsA level months 1 to 3 308 ± 9 259 ± 7 0.0001 Early rejection cpisodes 3 (0, 4) 3 (0, 5) NS Late rejection episodes 0 (0, 1) 1 (0, 4) <0.0001 Acute score month 6 1.75 ± 0.28 2.70 ± 0.36 0.04 Creatinine month I (.tmol/l) 131 ± 9 175 ± 9 0.001 Creatinine month 2 1 15 ± 5 170 ± 8 0.0001 Creatinine month 3 109 ± 4 174 ± 8 0.0001 Creatinine month 6 109 ± 4 182 ± I I 0.0001 Creatinine month 12 1 1 1 ± 4 188 ± 16 0.0001 Creatinine month 24 103 ± 3 199 ± 20 0.0001 a Values expressed as median (ruin, max). Table 5. Outcome defined by the change in serum creatinine from 6 to 24 mo Characteristic Stable Improving Cr < ± 20 jmol/l Cr - 20.tmol/L (a 39) (a 12) Declining Cr + 20 jtmolfl (a II) XCr6to24mo -3±2-32±3 +74 ±29b Crcatinine 6 mo 125 ± 6 165 ± 14h 187 ± 28 Crcatininc 12 mo 125 ± 6 145 ± 12 225 ± 42h Creatininc 24 mo 122 ± 6 133 ± I 3 260 ± 48h Protcinuria 24 mo (g/d) 0.29 ± 0.08 0.21 ± 0.07 1.42 ± 057h HLA (A + B) match 2 (0, 3) 1 (0, 2) 1 (0, 2) HLA DR match 1 (0, 2) 1 (0, 1 ) I (0, 1) Donor age (yr) 34 ± 2 22 ± 4h 48 ± 3h CsA level month 1 (p.gil 315 ± 12 288 ± 16 297 ± 18 CsA level month 2 290 ± I 5 265 ± 1 8 239 ± 21 CsA level month 3 270 ± 10 276 ± 23 267 ± 18 Early rejection episodes 3 (0, 4) 3 ( 1, 4) 3 (0, 5) Late rejection episodes 0 (0, 4) 1 (0, 2) 1 (0, 3)h ANOVA or Wilcoxon rank sum test. h p < 0.05, stable versus declining or stable versus improving. rejection ( I 2). Dim#{233}ny et al. found that the 6-mo chronic biopsy score correlated with graft loss and function at 2 or 3 yr posttransplant (14). Our study confirms the association between chronic pathology detected by protocol biopsy and a subsequent decline in ablograft function. Moreover, it suggests that chronic pathology that is predictive of diminished abbognaft function may be detected as early as 3 mo posttransplant. Diminished graft function has been associated with the use of renal grafts from young or old donors (i.e., < 10 or >50 yr) ( 15). Interestingly, it has also been reported that donor age falling between these extremes correlated with bong-term albognaft function and chronic albograft pathology ( 12,16). The current study confirms and extends these findings, because we found that patients with grafts from older donors carried an increased relative risk of having both an absolute creatininc 130 p.molil at 24 mo and a Cr6,4 + 20 mol/l. The OR was not based on a threshold age (e.g., >50 yr) ( 1 1 ), but was additive over an observed range of 9 to 55 yr of age. In addition to being associated with the 24-mo serum creatmine, donor age correlated with the chronic biopsy score at I 2 mo (r = 0.40, P < 0.001), 6 mo (r = 0.38, P = 0.001), and 3 mo (r = 0.26, P 0.03). Although it is possible that chronic pathology is preexistent in the abbograft from an older donor, this risk is minimized by donor selection. Indeed, our study

486 Journal of the American Society of Nephrobogy Biopsy Chronic Score 3.0 2.5 2.0 1.5 1.0 0.5 0.0 2 3 Month Post-transplant 6 12 Figure 1. Development of chronic albograft pathology over time in subgroups with stable (s), improving (0), or declining () albograft function. *ANOVA, P < 0.005 stable versus improving subgroup or stable versus declining subgroup. found that chronic biopsy scones, which were essentially 0 in the first 2 mo, increased progressively starting at month 3 posttransplant (Table 2). Moreover, the subgroup with declining function (zcr6_24 + 20 p.ruolil) had both older donors and a greater degree of acquired chronic pathology than the subgroup with stable function (zcr6.,4 <±20 jiruolll) (Table S and Figure 1 ). Therefore, in designing clinical trials to prevent chronic albograft nephropathy, donor age should be stratified for. Acute rejection is a well established risk factor for chronic rejection ( 10, 1 1, 1 7-20). For example, patients with one or more acute rejection episodes were estimated to have a risk ratio of chronic rejection 6.45 or 7.7 times higher than those with no rejection ( I 1, 18). However, it has been suggested that not all acute rejection episodes carry the same risk. Several groups have found that late (10, 1 7,20,2 1), but not early ( 10,20,22), acute rejection episodes are associated with chronic rejection. Our study found no correlation between early rejection episodes and the serum creatininc at 24 mo. On the other hand, we confirm the risk associated with late clinical rejection and demonstrate that late subclinical rejection is also an mdcpendent predictor of an increased serum creatininc at 24 mo. Because outcome might be improved by preventing late rejection, we sought independent variates predictive of late rejection. We were able to identify early clinical rejection episodes, prolonged cold ischcmic time, and inadequate immunosuppression (i.e., low CsA levels from 0 to 3 mo posttransplant) as predictors amenable to intervention. CsA has dramatically improved short-term renal allograft survival ( 1,2). However, debate exists regarding the impact of CsA on long-term albograft outcome (23-26). Most (I 1,17,27), but not all (20), studies found that low CsA doses were associated with diminished long-term graft function. The difficulty in interpreting these studies stems from the fact that the analyses were based on the CsA dose rather than the CsA level. In our study, CsA levels early posttransplant correlated negatively with the 24-mo serum creatinine. For those individuals whose mean 1- to 3-mo CsA level was >300 p.g/l, the adjusted OR ofhaving a creatinine 130 p.molll was 0.07 (95% CI, 0.01 to 0.43). Indeed, the long-term benefit of a higher CsA level in the early posttransplant period was, in fact, additive over an observed range of 1 97 to 606 jtg/l. Furthermore, because early CsA levels correlated negatively with both the 6-mo (r = -0.52, P < 0.0001) and 24-mo serum creatininc, but not with the Cr6_24, we propose that the principal robe of CsA is to preserve graft function during the phase of graft stabilization (i.e., 0 to 6 mo). This may explain why studies examining the effects of bate CsA withdrawal failed to find a negative impact on long-term abbograft function (20,23). In conclusion, we confirm the importance of late acute rejections and delayed graft function as risk factors for an elevated 24-mo serum creatininc. In addition, the benefit of adequate CsA levels in the early posttransplant period has been demonstrated. Finally, given the prognostic importance of both subclinical rejection and acquired chronic pathology found in the 6-mo protocol biopsy, superior long-term outcomes will likely require strategies that result in normal graft histology at 6 mo posttnansplant. Indeed, in the design of clinical prevention trials, protocol allograft biopsies at 6 mo could be useful as an early end point to assess the impact of a given immunosuppressive protocol. Note Added in Proof: Sen#{243}n et a!. (Kidney tnt 51 : 310-316, 1997) have recently documented an association between chronic changes in an early protocol biopsy and graft survival. Acknowledgments We are indebted to the nurses of the Transplant Clinic, the technobogists of the HLA laboratory, and most of all to our patients, whose interest in this project was equal to our own. References 1. The Canadian Multicentre Transplant Study Group: A randomized trial of cycbosporine in cadaveric renal transplantation. N Engi J Med 309: 809-815, 1983 2. European Multicentre Trial Group: Cyclosporin in cadaveric renal transplantation: One-year follow-up of a multicentre trial. Lancet 2: 986-989, 1983 3. Tullius S, Tilney N: Both alloantigen-dependent and -independent factors influence chronic albograft rejection. Transplantation 59: 313-318, 1995 4. Paul L: Chronic renal transplant loss. Kidney hit 47: 149 1-1499, I 995 5. Hunsicker L, Bennett L: Design of trials of methods to reduce late renal albograft loss: The price of success. Kidney Jut 48: 5120-5123, 1995 6. Kasiske B, Massy Z, Guijaro C, Ma I: Chronic renal allograft rejection and clinical trial design. Kidney fat 48: Sl 16-51 19, 1995 7. Rush D, Henry S. Ieffery J, Schroeder T, Gough I: Histological findings in early routine biopsies of stable renal albograft recipients. Transplantation 57: 208-21 1, 1994 8. Rush D. Ieffery I, Gough I: Sequential protocol biopsies in renal

Risk Factors of Declining Renal Allograft Function 487 transplant patients: Clinical-pathological correlations using the Banff schema. Transplantation 59: 51 1-514, 1995 9. Solez K, Axelsen R, Bcnediktsson H, Burdick I, Cohen A, Colvin R, Croker B, Droz D: International standardization of criteria for the histologic diagnosis of renal albograft rejection: The Banff working classification of kidney transplant pathology. Kidney mizt44: 41 1-422, 1993 10. Flechner 5, Modlin C. Serrano D, Goldfarb D, Papajcik D. Mastroianni B, Goormastic M, Novick A: Determinants of chronic renal allograft rejection in cycbosporine-treated recipients. Transplantation 62: 1235-1241, 1996 1 1. Almond P. Matas A, Gillingham K, Dunn D, Payne W. Gores P, Gruessner R, Najarian I: Risk factors for chronic rejection in renal albograft recipients. Transplantation 55: 752-757, 1993 12. Isoniemi H, Nurminen M, Tikkanen M, von Willebrand E, Krogerus L, Ahonen J, Eklund B, Hockerstedt K, Salmela K, Hayry P: Risk factors predicting chronic rejection of renal albografts. Transplantation 57: 68-72, 1994 13. Paul L, Hayry P, Foegh M, Dennis M, Mihatsch M, LaRsson E. Fellstrom B: Diagnostic criteria for chronic rejection/accelerated graft atherosclerosis in heart and kidney transplants: Ioint proposal from the Fourth Alexis Carrel Conference on Chronic Rejection and Accelerated Arteriosclerosis in Transplanted Organs. Transplant Proc 25: 2022, 1993 14. Dim#{233}nyE, Wahlberg I, Larsson E, Fclbstroru B: Can histopathological findings in early renal albograft biopsies identify patients at risk for chronic vascular rejection? Cliii Transplantation 9: 79-84, 1995 15. Yuge I, Cecka J: Sex and age effects in renal transplantation. In: Clinical Transplants, edited by Teraski P. Los Angeles. UCLA Tissue Typing Laboratory. 1991, pp 257-2f7 16. Isoniemi H, von Willebrand E, Krogerus L, Taskinen E, Ahonen I. Hayry P: The effect of donor age on kidney graft function and on histopathobogical findings. Transplant Proc 24: 328-329, 1992 17. Burke I, Pirsch I, Ramos E, Sabomon D, Stablein D, Van Buren D, West I: Long-term efficacy and safety of cycbosporine in renal-transplant recipients. N Engl J Med 33 1 : 358-363, 1994 18. Tesi R, Henry M, Elkhammas E. Ferguson R: Predictors of long-term primary cadaveric renal transplant survival. Cliii Transplantation 7: 345-352. 1993 19. Koyama H, Cccka I: Rejection episodes. In: Clinical Tra,isplants, edited by Terasaki P. Cecka I, Los Angeles, UCLA Tissue Typing Laboratory, 1992, pp 391-404 20. Massy Z, Guijarro C, Wiederkehr M, Ma I, Kasiske B: Chronic renal allograft rejection: Immunologic and noniruruunologic risk factors. Kidney tnt 49: 518-524, 1996 21. Basadonna G, Matas A, Gillingharu K, Payne W, Dunn D, Sutherland D, Gores P, Gruessner R, Najanian I: Early versus late acute renal albograft rejection: Impact on chronic rejection. Transplantation 55: 993-995, 1993 22. Lemstroru K, Koskinen P, Hayry P: Molecular mechanisms of chronic renal allograft rejection. Kidney tnt 48: 52-510, 1995 23. Hollander A, van Saase I, Kootte A, van Dorp W, van Bockel H, Van Es L, van der Woude F: Beneficial effects of conversion from cycbosporin to azathioprine after kidney transplantation. Lancet 345: 610-614, 1995 24. Mihatsch M, Ryffel B, Gudat F: The differential diagnosis between rejection and cyclosporine toxicity. Kidney tnt 48: 563-569, 1995 25. Lewis R: Long-term use of cyclosporine A does not adversely impact on clinical outcomes following renal transplantation. Kidney mnt 52: S75-S78, 1995 26. Remuzzi G, Perico N: Cycbosporine-induced renal dysfunction in experimental animals and humans. Kidney mt 48: S70-S74, 1995 27. Isoniemi H, Krogerus L. von Willebrand E, Taskinen E, Ahonen I, Hayry P: Histopathobogical findings in well-functioning, longterm renal albografts. Kidney mt 41 : 155-160. 1992