MEASUREMENT OF CHRONIC DAMAGE IN THE DONOR KIDNEY AND GRAFT SURVIVAL

Deep learning identified pathological abnormalities predictive of graft loss in kidney transplant biopsies

Interstitial fibrosis, tubular atrophy, and inflammation are major contributors to kidney allograft failure. Here we sought an objective, quantitative pathological assessment of these lesions to improve predictive utility and constructed a deep-learning-based pipeline recognizing normal vs. abnormal kidney tissue compartments and mononuclear leukocyte infiltrates. Periodic acid- Schiff stained slides of transplant biopsies (60 training and 33 testing) were used to quantify pathological lesions specific for interstitium, tubules and mononuclear leukocyte infiltration. The pipeline was applied to the whole slide images from 789 transplant biopsies (478 baseline [pre-implantation] and 311 post-transplant 12-month protocol biopsies) in two independent cohorts (GoCAR: 404 patients, AUSCAD: 212 patients) of transplant recipients to correlate composite lesion features with graft loss. Our model accurately recognized kidney tissue compartments and mononuclear leukocytes. The digital features significantly correlated with revised Banff 2007 scores but were more sensitive to subtle pathological changes below the thresholds in the Banff scores. The Interstitial and Tubular Abnormality Score (ITAS) in baseline samples was highly predictive of one-year graft loss, while a Composite Damage Score in 12-month post-transplant protocol biopsies predicted later graft loss. ITASs and Composite Damage Scores outperformed Banff scores or clinical predictors with superior graft loss prediction accuracy. High/intermediate risk groups stratified by ITASs or Composite Damage Scores also demonstrated significantly higher incidence of estimated glomerular filtration rate decline and subsequent graft damage. Thus, our deep-learning approach accurately detected and quantified pathological lesions from baseline or post-transplant biopsies and demonstrated superior ability for prediction of post-transplant graft loss with potential application as a prevention, risk stratification or monitoring tool.

Variation in use of procurement biopsies and its implications for discard of deceased donor kidneys recovered for transplantation

The use of procurement biopsies in deceased donor kidney acceptance is controversial. We analyzed Scientific Registry of Transplant Recipients data (n = 59 328 allografts, 2014-2018) to describe biopsy practices across US organ procurement organizations (OPOs) and examine relationships with discards, using hierarchical modeling to account for OPO and donor factors. Median odds ratios (MORs) provide the median of the odds that allografts with identical reported traits would be biopsied or discarded from 2 randomly drawn OPOs. Biopsies were obtained for 52.7% of kidneys. Biopsy use rose in a graded manner with kidney donor profile index (KDPI). Biopsy rates differed significantly among OPOs (22.8% to 77.5%), even after adjustment for KDPI and other donor factors. Discard rates also varied from 6.6% to 32.1% across OPOs. After adjustment for donor factors and OPO, biopsy was associated with more than 3 times the likelihood of discard (adjusted odds ratio [_95%LCL aOR_95%UCL ], _3.29 3.51_3.76 ). This association was most pronounced for low-risk (KDPI <20) kidneys (aOR, _5.45 6.47_7.69 ), with minimal impact at KDPI >85 (aOR, _0.88 1.15_1.51 ). Adjusted MORs for kidney discard and biopsy were greatest for low-risk kidneys. Reducing the rate of unnecessary biopsy and improving the accuracy of histologic assessments in higher KDPI organs may help reduce graft discard rates.

Validation of KDRI/KDPI for the selection of expanded criteria kidney donors

INTRODUCTION

KDRI / KDPI are tools use in kidney donor evaluation. It has been proposed as a substitute of, or complementary to preimplantation renal biopsy. These scores has not been validated in Spain.

OBJECTIVE

1) To investigate the concordance between KDPI and histological scores (preimplantation renal biopsy) and 2) To assess the relationship between KDRI, KDPI and histological score on graft survival in the expanded criteria donors group.

METHODOLOGY

Retrospective cohort study from 1 January 1998 until 31 December 2010.

RESULTS

During the study 120 donors were recruited, that resulted in 220 preimplantation renal biopsies. 144 (65%) grafts were considered suitable for kidney transplantation. 76 (34.5%) were discarded. Median follow up has been 6.4 years (sd 3.9). Median age 63.1 years (sd 8.2), males (145; 65.9%), non-diabetic (191; 86.8%) and without another cardiovascular risk factors (173; 78.6%). 153 (69.5%) donors died of cerebrovascular disease. There were significant differences in KDRI/KDPI score in both groups 1.56/89 (sd 0.22) vs 1.66/93 (sd 0.15), p<0.01). The KDPI showed moderate concordance and correlation with the histological score (AUC 0.64 / correlation coefficient 0.24, p <0.01). KDPI (HR 24.3, p<0.01) and KDRI (HR 23.3, p<0.01) scores were associated with graft survival in multivariate analysis.

CONCLUSION

1) KPDI and histological scores show moderate concordance. The utility of both scores as combined tools it has to be determined. 2) KDPI score, and especially KDRI score, are valid for estimating graft survival and combined with the biopsy can help to individualized decision making in the expanded criteria donors pool.

Strategies for an Expanded Use of Kidneys From Elderly Donors

The old-for-old allocation policy used for kidney transplantation (KT) has confirmed the survival benefit compared to remaining listed on dialysis. Shortage of standard donors has stimulated the development of strategies aimed to expand acceptance criteria, particularly of kidneys from elderly donors. We have systematically reviewed the literature on those different strategies. In addition to the review of outcomes of expanded criteria donor or advanced age kidneys, we assessed the value of the Kidney Donor Profile Index policy, preimplantation biopsy, dual KT, machine perfusion and special immunosuppressive protocols. Survival and functional outcomes achieved with expanded criteria donor, high Kidney Donor Profile Index or advanced age kidneys are poorer than those with standard ones. Outcomes using advanced age brain-dead or cardiac-dead donor kidneys are similar. Preimplantation biopsies and related scores have been useful to predict function, but their applicability to transplant or refuse a kidney graft has probably been overestimated. Machine perfusion techniques have decreased delayed graft function and could improve graft survival. Investing 2 kidneys in 1 recipient does not make sense when a single KT would be enough, particularly in elderly recipients. Tailored immunosuppression when transplanting an old kidney may be useful, but no formal trials are available.Old donors constitute an enormous source of useful kidneys, but their retrieval in many countries is infrequent. The assumption of limited but precious functional expectancy for an old kidney and substantial reduction of discard rates should be generalized to mitigate these limitations.

The Donor Kidney Biopsy and Its Implications in Predicting Graft Outcomes: A Systematic Review

Despite a growing organ shortage in the United States, many deceased donor kidneys removed for transplantation are discarded. Kidney biopsy findings often play a role in these discards, although it is not clear whether biopsies reliably inform acceptance decisions. Therefore, we carried out a systematic review of the medical literature on the utility of both procurement and implantation biopsies for predicting posttransplant outcomes. Between January 1, 1994 and July 1, 2014, 47 studies were published in the English language literature that examined the association between pretransplant donor biopsy findings from 50 or more donors (with more than half being from deceased donors) and either posttransplant graft failure, delayed graft function, or graft function. In general, study quality was poor. All were retrospective or did not indicate if they were prospective. Results were heterogeneous, with authors as often as not concluding that biopsy results did not predict posttransplant outcomes. The percent glomerular sclerosis was most often examined, and failed to predict graft failure in 7 of 14 studies. Of 15 semiquantitative scoring systems proposed, none consistently predicted posttransplant outcomes across studies. Routine use of biopsies to help determine whether or not to transplant a kidney should be reexamined.

The role of procurement biopsies in acceptance decisions for kidneys retrieved for transplant

BACKGROUND AND OBJECTIVES

There is a shortage of kidneys for transplant, and many patients on the deceased donor kidney transplant waiting list would likely benefit from kidneys that are currently being discarded. In the United States, the most common reason given for discarding kidneys retrieved for transplant is procurement biopsy results. This study aimed to compare biopsy results from discarded kidneys with discard attributed to biopsy findings, with biopsy results from comparable kidneys that were successfully transplanted.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective, observational, case-control study, biopsy reports were examined from 83 kidneys discarded in 2010 due to biopsy findings (cases), 83 contralateral transplanted kidneys from the same donor (contralateral controls), and 83 deceased donors randomly matched to cases by donor risk profile (randomly matched controls). A second procurement biopsy was obtained in 64 of 332 kidneys (19.3%).

RESULTS

The quality of biopsy reports was low, with amounts of tubular atrophy, interstitial inflammation, arteriolar hyalinosis, and acute tubular necrosis often not indicated; 69% were wedge biopsies and 94% used frozen tissue. The correlation between first and second procurement biopsies was poor; only 25% of the variability (R(2)) in glomerulosclerosis was explained by biopsies being from the same kidney. The percentages of glomerulosclerosis overlapped substantially between cases, contralateral controls, and randomly matched controls: 17.1%±15.3%, 9.0%±6.6%, and 5.0%±5.9%, respectively. Of all biopsy findings, only glomerulosclerosis>20% was independently correlated with discard (cases versus contralateral controls; odds ratio, 15.09; 95% confidence interval, 2.47 to 92.41; P=0.003), suggesting that only this biopsy result was used in acceptance decisions. One-year graft survival was 79.5% and 90.7% in contralateral and randomly matched controls, respectively, versus 91.6% among all deceased donor transplants in the Scientific Registry of Transplant Recipients.

CONCLUSIONS

Routine use of biopsies could lead to unnecessary kidney discards.

Early changes in scores of chronic damage on transplant kidney protocol biopsies reflect donor characteristics, but not future graft function

The amount of irreversible injury on renal allograft biopsy predicts function, but little is known about the early evolution of this damage. In a single-center cohort, we examined the relationship between donor-, recipient-, and transplantation-associated factors and change in a morphometric index of chronic damage (ICD) between protocol biopsies performed at implantation and at 2-3 months. We then investigated whether early delta ICD predicted subsequent biochemical outcomes. We found little evidence to support differences between the study group, who had undergone serial biopsies, and a contemporaneous control group, who had not. In allografts with serial biopsies (n = 162), there was an increase in ICD between implantation (median: 2%, IQR:0-8) and 2-3 months post-transplant (median 8% IQR:4-15; p < 0.0001). Donation from younger or live donors was independently associated with smaller early post-transplant increases in ICD. There was no evidence for a difference in delta ICD between donation after cardiac death vs. donation after brain death, nor association with length of cold ischemia. After adjustment for GFR at the time of the second biopsy, delta ICD after three months did not predict allograft function at one yr. These findings suggest that graft damage develops shortly after transplantation and reflects donor factors, but does not predict future biochemical outcomes.

The cutting (w)edge--comparative evaluation of renal baseline biopsies obtained by two different methods

BACKGROUND

The assessment of donor-derived damage of transplanted kidneys might be instrumental for estimating donor organ quality and for predicting short- and long-term organ outcome. In the present study, we report a new standardized method for obtaining pre-transplant kidney biopsy specimens. Instead of taking wedge biopsies (WBs), a skin punch biopsy (PB) tool was utilized to obtain standardized biopsy samples that also represented deeper cortical zones.

METHODS

We compared 147 PB specimens and 114 WBs with respect to the number of glomeruli and arterial vessels they contained. The performance of the two biopsy methods in detecting glomerular damage, interstitial fibrosis/tubular atrophy (IF/TA) and arteriosclerosis was determined by evaluation of subsequent transplant core biopsies of the patients. Statistical comparison employed Kruskal-Wallis and kappa (κ) tests.

RESULTS

Significantly more PB samples (89%) than WBs (66%) were diagnostically adequate according to the Banff criteria. Despite a higher number of glomeruli in WBs (34.6 versus 21.7 in punch biopsies), arteries were present in only 68% of WBs but could be found in 93% of punch biopsies. The comparison of findings in pre-transplant biopsies with lesions in corresponding post-transplant core biopsies revealed a superior diagnostic concordance for IF/TA and arteriosclerosis for punch biopsies than for WBs, reaching kappa values of 0.823 versus 0.729 and 0.661 versus 0.516, respectively.

CONCLUSION

The use of skin PB tools for obtaining baseline biopsies from transplanted kidneys is a safe and effective method for assessment of donor-derived damage of the organ.

Assessment of kidney organ quality and prediction of outcome at time of transplantation

The critical importance of donor organ quality, i.e., number of surviving nephrons, ability to withstand injury, and capacity for repair in determining short- and long-term outcomes is becoming increasingly clear. This review provides an overview of studies to assess donor kidney quality and subsequent transplant outcomes based on clinical pathology and transcriptome-based variables available at time of transplantation. Prediction scores using clinical variables function when applied to large data sets but perform poorly for the individual patient. Histopathology findings in pre-implantation or post-reperfusion biopsies help to assess structural integrity of the donor kidney, provide information on pre-existing donor disease, and can serve as a baseline for tracking changes over time. However, more validated approaches of analysis and prospective studies are needed to reduce the number of discarded organs, improve allocation, and allow prediction of outcomes. Molecular profiling detects changes not seen by morphology or captured by clinical markers. In particular, molecular profiles provide a quantitative measurement of inflammatory burden or immune activation and reflect coordinated changes in pathways associated with injury and repair. However, description of transcriptome patterns is not an end in itself. The identification of predictive gene sets and the application to an individualized patient management needs the integration of clinical and pathology-based variables, as well as more objective reference markers of transplant function, post-transplant events, and long-term outcomes.

Prediction of ESRD in pauci-immune necrotizing glomerulonephritis: quantitative histomorphometric assessment and serum creatinine

Background

Clinical and pathologic features that predict outcome have important potential application in patients with pauci-immune necrotizing glomerulonephritis (usually antineutrophil cytoplasmic antibody–associated vasculitis). This study examines the predictive value of simple quantitative renal histologic measurements in a large cohort with extended follow-up.

Study Design

Cohort study.

Setting & Participants

390 consecutive patients with pauci-immune necrotizing glomerulonephritis at a single hospital (1983-2002); 90 patients underwent repeated kidney biopsy during follow-up.

Predictors

Age and serum creatinine concentration at biopsy, antineutrophil cytoplasmic antibody specificity, percentage of normal glomeruli, percentage of glomeruli with active lesions, and index of chronic damage (quantitative measurement of established cortical damage) in the initial kidney biopsy for all patients. The same factors were assessed in both biopsy specimens for patients undergoing an additional biopsy.

Outcomes & Measurements

End-stage renal disease and patient survival.

Results

Mortality at 1 and 5 years was 23% and 40%, respectively: standardized mortality ratio, 4.74 (95% CI, 3.62-6.32). End-stage renal disease was reached by 14% and 18% at 1 and 5 years, respectively. In multivariable analysis, serum creatinine level at biopsy and percentage of normal glomeruli in the initial biopsy specimen were the best predictors of kidney survival. C Statistics were 0.80 for creatinine level alone and 0.83 for creatinine level with normal glomeruli. In patients undergoing an additional biopsy, rapid progression in the index of chronic damage and serum creatinine level at the second biopsy were associated with kidney survival in multivariable analysis.

Limitations

Retrospective analysis. External validity of the index of chronic damage requires further assessment. Selection bias may influence repeated biopsy analyses.

Conclusions

Serum creatinine level at biopsy best predicts kidney survival in patients with pauci-immune necrotizing glomerulonephritis overall.

Time-zero renal biopsy in living kidney transplantation: a valuable opportunity to correlate predonation clinical data with histological abnormalities

BACKGROUND

Living kidney donation is increasing as a partial solution for wait-listed patients. Despite properly followed guideline criteria for donor selection, current reports identify unsuspected renal pathology at preimplantation or time-zero biopsy (T0-RBx).

METHODS

T0-RBx was evaluated for following: interstitial fibrosis (IF), tubular atrophy (TA), arteriolar hyalinosis (AH), mesangial increase (MI), and glomerulosclerosis (GS). Predonation data were demography, body weight, body mass index (BMI), systolic/diastolic blood pressure (BP), serum creatinine (SCr), estimated glomerular filtration rate (eGFR), and proteinuria.

RESULTS

Two hundred nineteen T0-RBx were analyzed. Of these 54.4% had abnormal findings, namely, IF in 29%, TA in 13%, MI in 12%, AH in 10%, and GS in 10%. Mean clinical data were as follows: age 35.4+/-10 years, weight 66.27+/-10.14 kg, BMI 25.53+/-2.99, systolic BP 115+/-9 mm Hg, diastolic BP 74+/-7 mm Hg, SCr 0.91+/-0.25 mg/dL, eGFR 96+/-16.65 mL/min, and proteinuria 70.25+/-62.8 mg/24 hr. A total of 56.7% were women. IF correlated to age (r=0.22, P=0.001) and SCr (r=0.19, P=0.005); TA to diastolic BP (r=0.15, P=0.03) and proteinuria (r=0.20, P=0.009); AH to SCr (r=0.15, P=0.02) and eGFR (r=-0.16, P=0.018); MI to BMI (r=0.13, P=0.047). Multivariate analysis failed to sustain the significant associations found on bivariate analysis, most likely due to a low event/parameter relation and sample size.

CONCLUSIONS

A significant correlation was established between T0-RBx findings and clinical predonation parameters. Whether these mild histologic findings at the time of kidney donation represent a higher risk for the remaining kidney ought to be evaluated during follow-up. In an era, when living kidney donation is increasing, we advise closer donor surveillance to modify risk factors that participate in kidney damage progression.

A systematic review of kidney transplantation from expanded criteria donors

BACKGROUND

During the past few years, there has been renewed interest in the use of expanded criteria donors (ECD) for kidney transplantation to increase the numbers of deceased donor kidneys available. More kidney transplants would result in shorter waiting times and limit the morbidity and mortality associated with long-term dialysis therapy.

STUDY DESIGN

Systematic review of the literature.

SETTING & POPULATION

Kidney transplantation population.

SELECTION CRITERIA FOR STUDIES

Studies were identified by using a comprehensive search through MEDLINE and EMBASE databases. Inclusion criteria were case series, cohort studies, and randomized controlled trials assessing kidney transplantation in adult recipients using ECDs.

PREDICTOR

A special focus was given to studies comparing the evolution of kidney transplantation between standard criteria donors (defined as a donor who does not meet criteria for donation after cardiac death or ECD) and ECDs (defined as any brain-dead donor aged > 60 years or a donor aged > 50 years with 2 of the following conditions: history of hypertension, terminal serum creatinine level >or= 1.5 mg/dL, or death resulting from a cerebrovascular accident).

OUTCOMES

Criteria used to define and select ECDs, practice patterns, long-term outcomes, early complications, and some patient issues, such as selection criteria and immunosuppressive management.

RESULTS

ECD kidneys have worse long-term survival than standard criteria donor kidneys. The optimal ECD kidney for donation depends on adequate glomerular filtration rate and acceptable donor kidney histological characteristics, albeit the usefulness of biopsy is debated.

LIMITATIONS

This review is based mainly on data from observational studies, and varying amounts of bias could be present. We did not attempt to quantitatively analyze the effect of ECD kidneys on kidney transplantation because of the huge heterogeneity found in study designs and definitions of ECD.

CONCLUSIONS

Based on the available evidence, we conclude that patients younger than 40 years or scheduled for kidney retransplantation should not receive an ECD kidney. Patients 40 years or older, especially with diabetic nephropathy or nondiabetic disease, but a long expected waiting time for kidney transplantation, show better survival receiving an ECD kidney than remaining on dialysis therapy.

Can donor implantation renal biopsy predict long-term renal allograft outcome?

BACKGROUND

Donor kidney implantation biopsy (IB) is performed on a regular basis, particularly as part of clinical studies.

OBJECTIVE

To determine the utility of donor implantation renal biopsy to predict the long-term renal allograft outcome.

METHODS

A Medline search for studies in English was performed with the following key words: implantation biopsy, renal transplantation and long-term outcome.

RESULTS

Sixteen trials involving 8,122 kidney transplants were identified, of which 6 were prospective studies. The histological abnormalities were scored mainly by the Banff schema and the graft outcome was defined either by delineating the delta changes in the pathology score or glomerular filtration rate. Normal histology with a well-functioning renal allograft had a favorable outcome. The extent to which the baseline tubular atrophy, interstitial fibrosis, glomerulosclerosis and vascular changes had on the long-term outcome varied from one study to another.

CONCLUSION

Abnormal IB has a better chance of predicting early graft outcome. The review questions the current wisdom for routine IB on all donors. In some donor kidneys, a biopsy provides significant prognostic information, such as older donor kidney, those with history of hypertension, diabetes, cardiovascular disease, and kidneys with abnormal creatinine. Future research on IB is necessary to find a more useful method to predict the long-term transplant outcome.

Quantitative Digital Histochemistry With Methenamine Silver Staining in Renal Allograft Biopsies Excluding Pure Chronic Allograft Nephropathy Cases

Deterioration of renal function is correlated with irreversible damage in chronic diseases. Recently we described a digital quantitative histochemistry method, relying on periodic acid methenamine silver (PAMS) staining to determine the chronic renal lesions. This index was strongly correlated with progressive deterioration of renal function in grafts with chronic allograft nephropathy (CAN). Herein the method has been applied to a cohort of renal allografts which were biopsied for various reasons, we sought to highlight its value to quantify chronic graft damage. Forty-four renal allograft biopsies from 37 patients with elevated serum creatinine values (SCr) underwent light microscopic image analysis (Mediscope, Dokuz Eylül University, Clinical Engineering Department, Izmir, Turkey) of the PAMS-stained area percentage (SAP). SCr was recorded at four intervals to overcome acute effects: the under SCr value before (SCr1) and after a biopsy within 3 months (SCr3), SCr at the time of the biopsy (SCr2), and the latest value (SCr4). The PAMS-SAP scores were strongly associated with increased interstitial fibrosis and tubular atrophy Banff scores (Kruskal-Wallis test, P = .006 and P = .003, respectively). There was a moderate positive correlation between PAMS and SCr3 (Pearson correlation test, P = .04, r = .312), and a strong positive correlation between time from transplantation to biopsy (Pearson correlation test, P << .000, r = .532). The present results show that PAMS-SAP seems to be of value to quantify renal scarring in allograft biopsies, reflecting four compartments. The strong correlation with time is noteworthy especially as a probable reflection of aging of the renal allograft.

Evaluation of pre-implantation kidney biopsies: Comparison of Banff criteria to a morphometric approach

BACKGROUND

Donor glomerulosclerosis, interstitial fibrosis, and fibrous intimal thickening correlate with graft outcome. We evaluate chronic lesions in donor biopsies according to Banff criteria and with a morphometric technique to ascertain their predictive value on graft outcome.

METHODS

We evaluated 77 cadaveric donor biopsies according to Banff criteria. Glomerulosclerosis was expressed as the percentage of global sclerotic glomeruli. The following morphometric parameters were obtained: cortical interstitial volume fraction (Vvint/c), cortical glomerular volume fraction (Vvglom/c), mean glomerular volume (Vg), mean and maximal intimal arterial volume fraction (Vvintima/art), and Vvintima/art of the largest artery. We evaluated the correlation of histologic lesions with delayed graft function, 3 months' glomerular filtration rate (GFR), and death-censored graft survival.

RESULTS

Multivariate logistic regression showed that delayed graft function was associated with cv score [relative risk (RR) 4.2 and 95% CI 1.1 to 16.0) and glomerulosclerosis (RR 1.06 and 95% CI 1.01 to 1.13). Stepwise regression showed that Vvint/c and glomerulosclerosis were independent predictors of 3 months' GFR (R= 0.62, P= 0.0001). Repeated analysis not considering morphometric parameters showed that glomerulosclerosis, cv score and ci score were independent predictors of 3 months' GFR (R= 0.64, P= 0.0001). A donor chronic damage score was generated considering glomerulosclerosis, cv score and ci score. This score after adjusting for clinical variables was associated with 3 months' GFR (R= 0.71, P < 0.0001) and death-censored graft survival (RR 2.2 and 95% CI 1.3 to 3.7).

CONCLUSION

Combined evaluation of donor glomerulosclerosis, chronic vascular and interstitial damage according to Banff criteria allows a precise prediction of graft outcome. Morphometric evaluation of donor biopsies does not improve the predictive value of semiquantitative grading.

Methenamine silver staining quantitative digital histochemistry in chronic allograft nephropathy

Renal function and final outcome of renal allografts have been correlated with irreversible damage. This study describes a quantitative histochemical method relying on periodic acid methenamine silver (PAMS) staining of all renal compartments. Among 60 renal allograft biopsies from 43 patients, 15 biopsies showing pure chronic allograft nephropathy were selected to determine PAMS-stained area percentage (SAP), using image analysis with quantitative histochemistry. Of the 15 cases, 9 (60%) were grade I and 6 (40%) were grade II chronic allograft nephropathy (CAN). The mean serum creatinine (sCr) value was 1.86 +/- 0.47 for allograft biopsies. The mean (+/-SD) SAP for the implantation biopsies was 10.58 +/- 1.87%, and for allograft biopsies 25.26 +/- 9.67 (P <<.000). The serum creatinine (sCr) values for grade I versus II CAN were 1.63 +/- 0.24 versus 2.20 +/- 0.54 mg/dL, respectively (P=.019), and SAP values were 18.97 +/- 0.24 versus 34.7 +/- 5.89 (P=.003). There was a strong positive correlation between sCr values and SAP (P=.005; r=0.64). These findings show the PAMS approach to be a useful alternative method for reflecting damage in more than one compartment of the renal tissue. Also, the method can discriminated implantation and allograft biopsies as well as grade I and II CAN cases. The series is small for a multivariate analysis of the value of SAP measurements in PAMS-stained sections as a prognosticator, but the data support its use.