MO049: Correlation of Findings in Urinary Sediment Microscopy and Histological Lesions in Kidney Biopsy: Red Flags Not to be Missed

BACKGROUND AND AIMS

Urinary sediment (U-Sed) is a noninvasive laboratory test that can be performed by an automated analyzer or manually by trained personnel. Manual U-Sed remains the diagnostic standard because it excels at distinguishing isomorphic from dysmorphic red blood cells, identifying renal tubular epithelial cells, lipids, crystals and the composition of casts. Findings in U-Sed reflect damage that is occurring within the kidney, which can be documented by kidney biopsy. This study aimed to investigate the prevalence of a complete profile of U-Sed particles and its associations with histological lesions on kidney biopsy, regardless of renal diagnosis.

METHOD

This retrospective study included 131 patients who had contemporary manual U-Sed evaluation and kidney biopsy at our institution, from 2018 to 2021. Renal transplant patients were excluded. A comprehensive set of urinary particles and histological lesions were quantified, and we analyzed their associations.

Urinary particles evaluated included casts, erythrocytes, leukocytes, renal tubular epithelial cells, urothelial transitional cells (superficial and deep), lipids, crystals, squamous cells and bacteria. They were semi-quantified from 0 (absent) to 3 + . Renal biopsies samples were reviewed, and a systematic evaluation of 32 histological lesions was performed. When present, lesions were semi-quantified from 0 (absent) to 3 + .

Appropriate tests were performed STATA v.16.1.

RESULTS

We found an elevated frequency of findings suggestive of proliferative renal disease, such as dysmorphic hematuria (n = 71, 54.2%), leukocyturia (n = 62, 47.3%), renal tubular epithelial cells (n = 53, 40.5%) and lipiduria (n = 45, 34.4%), and a low frequency of particles evoking urological damage, such as isomorphic hematuria (n = 29, 22.1%), crystals (n = 12, 9.2%) and urothelial transitional cells (n = 26, 9.9%).

The association of histological lesions and urinary particles was explored with a multivariate model that identified U-Sed characteristics, which favored the presence of acute tubular necrosis, endocapillary hypercellularity, neutrophils and/or karyorrhexis, wire loops and/or hyaline deposits, fibrinoid necrosis and cellular/fibrocellular crescents (summarized in Table 1).

CONCLUSION

In a population of patients submitted to kidney biopsy, we found that the presence of some urinary particles (renal tubular epithelial cells, lipids and dysmorphic erythrocytes), which are seldom reported by automated analyzers, conferred an increased likelihood of active proliferative histological lesions. It is important not to misidentify them, as their presence are red flags for relevant proliferative histological lesions. Moreover, given the flare/remission characteristics of proliferative glomerular disease, U-Sed could play a major role in measuring the degree of activity without requiring repeat kidney biopsies.

Case report: rivaroxaban related nephropathy

The characteristics of direct oral anticoagulants (DOACs) make them more appealing for prevention of thromboembolic events than vitamin K antagonists (VKA). Despite that, both classes have been a recognized as a cause of anticoagulant related nephropathy (ARN). Herein we describe a case of a 72-year-old man, with chronic kidney disease (CKD), medicated with rivaroxaban, who presented with acute kidney injury (AKI) and microscopic hematuria. The kidney biopsy revealed anticoagulant related-nephropathy. Rivaroxaban was suspended, the patient showed improvement of renal function and apixaban was prescribed. This case emphasizes the need for careful monitoring of serum creatinine when these drugs are prescribed, especially in high risk groups.

Membranous nephropathy with collapse in a HIV negative patient; a case report with a 34-month follow-up

Membranous nephropathy (MN) is a common cause of nephrotic syndrome (NS) in nondiabetic adults. Collapsing nephropathy (CN) is a morphological pattern that is usually classified as a variant of focal segmental glomerulosclerosis (cFSGS). The simultaneous presence of both MN and CN is rare and their combination usually foresees an unfavorable outcome. Herein, we describe a case report of a patient with PLA2 R-associated MN with collapse, its treatment and clinical course.

MO088CLINICOPATHOLOGICAL FEATURES OF THROMBOTIC MICROANGIOPATHY

Background and Aims

TMA is a rare and severe endothelial lesion with thrombus formation and vascular occlusion with organ damage. It can be a complication of several clinical conditions. The aim of this study was to characterize clinical and pathological findings of patients with confirmed kidney TMA.

Method

We performed a retrospective observational descriptive study that analyzed all patients with TMA diagnosed by kidney biopsy, in two hospital centers, from January 2015 until December 2020. Clinical, laboratorial, pathologic characteristics were analyzed as also therapeutic performed and kidney and patient outcomes.

Results

Our sample had 14 patients, the majority female (n=11, 78%) with a mean age of 45±10 years-old and 12 (80%) were Caucasian. Six (40%) had past medical history of HTA, 2 (13%) had Multiple Myeloma, 4 (26%) transplant (3 kidney, 1 lung) and none had positive viral serology’s. Prodromal symptoms included diarrhea in 2 (13%) patients, neurological in 3 (20%) and previous infection in 3 (20%).

Mean laboratorial values were: Hemoglobin 7.8 g/dL, platelets 161.000/uL; LDH 586 UL; bilirubin 1.38 mg/dL, haptoglobin 1,55 g/L. Only 5 had schistocytes. ADAMTS13 activity was >10% in all performed and in all, Coombs test were negative.

C3 was consumed in 3 (20%) patients and C4 in 2 (13%) but complement phenotypic study was normal in all performed patients. Auto-immune study revealed: 1 positive ANA, dsDNA negative in all but one with positive c1q antibody. One had positive antiphospholipid syndrome (AFS) antibodies and one scleroderma antibodies.

Main kidney presentation was acute kidney injury in 8 (53%) patients, with mean eGFR 14ml/min/1,73m2. Mean proteinuria was 2,5 g/24h and half (50%) had hematuria.

Kidney biopsies had a mean of 11,85 glomerulus, of which 14% sclerotic, mean interstitial fibrosis and tubular atrophy score 1,7. Acute tubular necrosis was present in 7 (46%) and inflammatory infiltrate in all, endotheliosis in 13 (86%), mesangiolysis in 3 (20%), arteriolar thrombus in 10 (66%), glomerular thrombus in 6 (40%), ischemic glomerulus in 12 (80%) and double-contour appearance in 7 (46%).

TMA etiologies were the following: 2 malignant hypertension, 2 proteasome inhibitor (PI), 1 scleroderma, 1 lupus, 1 AFS, 2 calcineurin and mammalian target of rapamycin inhibitors, 2 antibody mediated rejection (AMR), 1 methylmalonic acidemia and 2 undetermined.

Treatment performed encompassed: hypertension management, withdrawal od PI, changing immunosuppression, AMR treatment, cyanocobalamin, lupus induction treatment and eculizumab.

Kidney recovery was observed in 8 patients (53%). Patient survival at 6 months was 73%.

Conclusion

These study results highlight the vast context of conditions that TMA can appear. Most of them had only with mild or even absent clinical and laboratory features. Therefore, a high index of suspicion is required to diagnose TMA, allowing targeted treatment to preserve of kidney function.

MO196KIDNEY INVOLVEMENT IN WALDENSTROM MACROGLOBULINEMIA AND IGM MONOCLONAL GAMMOPATHY

Background and Aims

Renal manifestations of IgM gammopathy are less common than those seen in patients with multiple myeloma. However, a wide spectrum of kidney diseases has been described in previous publications. We aim to characterize kidney involvement in patients with Waldenström Macroglobulinemia and IgM-secreting B cell lymphoproliferative disorders.

Method

We retrospectively studied 7 patients with a circulating monoclonal IgM and renal histology showing evidence of monoclonal immunoglobulin deposits or lymphomatous infiltration. Demographic, clinical and laboratory data were collected.

Results

Of the 7 patients studied, four (57%) were male and the median age was 68 years old (range 41-79). Among the 7 patients, 5 met criteria for Waldenström Macroglobulinemia after bone marrow biopsy; none of them had hyperviscosity syndrome. Four patients presented with nephrotic syndrome and all had impaired renal function and hypertension. Four patients had microscopic hematuria and only one patient showed no proteinuria. Mean serum creatinine levels were 2.9mg/dL. Renal biopsy showed different patterns of renal injury, including typical intracapillary monoclonal deposits disease (5 patients), membranoproliferative glomerulonephritis with cryoglobulinemia (1 patient), AL-amyloidosis (1 patient) and interstitial lymphoplasmacytic infiltration with CD20+ lymphocytes associated with minimal change disease. Follow-up data were obtained in 4 patients: 3 underwent chemotherapy but only one achieved complete remission and 2 progressed to end-stage renal disease.

Conclusion

Although rare, Waldenström Macroglobulinemia and IgM gammopathy are responsible for diverse manifestations of renal disease. A prompt diagnosis is of utmost importance in order to ensure early start of therapy, which should be directed at the underlying hematologic disorder, to improve renal survival.

Successful treatment of collapsing focal segmental glomerulosclerosis in a patient

Focal segmental glomerulosclerosis (FSGS) is a recognized cause of renal disease worldwide. The collapsing variant is distinct from the others, characterized clinically by a more severe nephrotic syndrome generally resistant to immunosuppressive therapy. It is known that a great number of patients progress to end-stage renal disease. Recognizing this lesion in biopsy is frequently challenging owing to the focal nature of the process which highlights the need for keeping a high index of suspicion for the diagnosis. We report and discuss a case of a non-HIV collapsing FSGS, followed by a complete (unexpected) renal recovery after an oral corticosteroid course.

Rubrics for mortality: a real-world observational long-term lupus nephritis cohort

In this study, we aimed to evaluate long-term patient survival according to demographic data, clinical manifestations of systemic lupus erythematosus (SLE) and previous and current treatments, collected retrospectively. Patient selection required a minimum of four American College of Rheumatology revised criteria for SLE, biopsy-proven lupus nephritis (LN) available for reclassification according to the modified National Institutes of Health proposal for activity and chronicity indices and a minimum follow-up of at least three years since the last renal biopsy. Selection criteria were fulfilled in 25 patients followed for a median of 21 years. Based on the last renal biopsy, an equal number of patients were thus classified as class I/II and IV (n=8) and class III and V (n = 4). The mortality rate for LN was 14%. Having ever been diagnosed with glomerulonephritis (GN) type III or type IV but not class IV alone (p = 0.046), a higher histological chronicity index at the last renal biopsy (p = 0.022), not attaining renal remission one year after induction therapy (p = 0.004), end-stage renal disease on dialysis (p = 0.033) and the extra-renal Systemic Lupus International Collaborating Clinics Damage Index score (p = 0.017) were all significantly associated with mortality. Our results may provide important clues for strict observation protocols in particular categories of LN patients with long-standing disease.

P0481MORTALITY PREDICTORS IN ANCA-ASSOCIATED VASCULITIS AND ANTI-GLOMERULAR BASEMENT MEMBRANE DISEASE

Background and Aims

The antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and anti-glomerular basement membrane (GBM) disease are autoimmune diseases that cause necrotizing crescentic glomerulonephritis. These diseases portend an increased risk of end-stage kidney disease and death. The main objective of our study was to identify predictors of mortality in patients with these diseases.

Method

Retrospective analysis of patients diagnosed with AAV and anti-GBM disease by renal biopsy performed between 2013 and 2019. The minimum duration of follow-up was 6 months. Demographic, laboratory and histological characteristics were studied. The primary endpoint was death due to any cause. Continuous variables were presented as means or medians, according to normality and categorical variables presented as frequencies. The comparison between subgroups of patients was performed using the Wilcoxon, Fisher exact test or t-test, chi-square test, according to normality. Univariate and multivariate logistic regression models were fitted to identify variables associated with death. STATA 14.2 statistical package was used and p < 0.05 was considered statistically significant.

Results

We identified 40 patients, 37 (95%) were caucasian and 22 (55%) female. The mean age was 69 years, serum creatinine 3.4 (2.3 – 4.5) mg/dL, eGFR 14 (11-23) ml/min/1.73 m2 and proteinuria 1.42 (0.75 – 3.38) g/day. Twenty-seven (68%) had a past medical history of hypertension and 3 (8%) type two diabetes. Thirty-three (83%) presented with constitutional symptoms and 12 (30%) had pulmonary manifestations, while the other manifestations were less frequent. The average time between symptoms presentation and therapy initiation was 119 days. Mean follow-up was 1094 days. Renal biopsy showed grade 0 interstitial fibrosis and tubular atrophy in 5 patients (13%), grade 1 in 13 (33%), grade 2 in 8 (20%) and grade 3 in 14 (35%). The majority had no vessel involvement (24, 60%) and grade 2 acute tubular necrosis (18, 45%). Inflammatory infiltrate was present in 25 patients (63%). At 6 and 12 months, 15 (38%) and 9 (23%) were dialysis dependent, respectively. All patients were treated with prednisolone, 14 (35%) with cyclophosphamide, 15 (38%) with rituximab and 14 (35%) underwent plasmapheresis. Eighteen (45%) patients were maintained on azathioprine. At the end of follow-up, 13 patients had died and 2 relapses occurred. Eleven (46%) patients presented at least one serious infectious episode. Older age (OR 1.10, 95% [1.01-1.20], p=0.035), higher diastolic blood pressure (OR 1.09, 95% [1.00-1.12], p=0.046), and lower C3 levels (OR 0.003, 95% [0.000-0.525], p=0.027) were associated with higher mortality on univariate analysis. On multivariate analysis, only higher diastolic blood pressure remained significant. Pathology findings and serum creatinine values were not associated with higher mortality

Conclusion

Overall mortality in AAV and anti-GBM has decreased over the last two decades with the use of immunosuppressive therapies. However, mortality rates remain high and most deaths occur during the first year following diagnosis. Early detection of infections with prompt initiation of treatment may help to reduce mortality. Additionally, the identification of risk factors associated with a higher risk of mortality and that could allow individualization of therapy remains a challenge.

P0462HEMODIALYSIS PREDICTORS IN ANCA-ASSOCIATED VASCULITIS AND ANTI-GLOMERULAR BASEMENT MEMBRANE DISEASE

Background and Aims

Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and anti-glomerular basement membrane (GBM) disease are autoimmune diseases frequently associated with poor renal outcomes namely hemodialysis. Therefore, the aim of this study was to identify predictors of renal replacement therapy (RRT) at six months in patients with ANCA-associated vasculitis and/or anti-glomerular basement membrane disease.

Method

We performed a single center observational, retrospective study in 40 patients with ANCA-associated vasculitis and/or anti-GBM disease diagnosed between January 2013 and June 2019.

Clinical, analytical and histological variables were included as well as therapeutic regimens and outcomes. The primary endpoint was renal replacement therapy (RRT) at six months.

Continuous variables were presented as means or medians, according to normality and categorical variables presented as frequencies. The comparison between subgroups of patients was performed using the Wilcoxon, Fisher exact test or t-test, chi-square test, according to normality. Univariate logistic regression model was fitted to identify variables associated with renal replacement therapy. STATA 14.2 statistical package was used and p <0.05 was considered statistically significant.

Results

We identified 40 patients, with a mean age of 69 years-old, 18 (45%) were male, 37 (95%) Caucasian. Twenty-seven (68%) had hypertension and 3 (8%) diabetes. The majority (33, 83%) presented with constitutional symptoms. Pulmonary manifestations were seen in 12 (30%) and gastrointestinal in 5 patients (12%). The other symptoms were rare. The mean systolic blood pressure was 140 mmHg and mean diastolic blood pressure 73 mmHg. The mean hemoglobin in hospital stay was 9,4g/dL, albumin 3.0 mg/dL, erythrocyte sedimentation rate 77mm/h, C3 1,11 UQ, C4 0,30 UQ, proteinuria 1,42 gr/24h, hematuria 279 erythrocytes, serum creatinine 3,4 mg/dL, eGFR 14 ml/min/m2, uric acid 7.1 mg/dL. The average ANCA MPO titles were 382 UQ/L, PR3 751UQ/L and GBM 883UQ/L. During hospital stay 11 patients (28%) needed dialysis.

Renal biopsy showed interstitial fibrosis and tubular atrophy grade 0 in 5 patients (13%), grade 1 in 13(33%), grade 2 in 8 (20%) and grade 3 in 14 (35%). The majority had no vessel involvement 24 (60%). Acute tubular necrosis was absent in 13 (33%) patients, grade 1 in 9 (23%) and grade 2 in 18 (45%). Inflammatory infiltrate was present in 25 patients (63%).

Regarding treatment, 38 (95%) of patients received pulse methylprednisolone and all prednisolone. Rituximab was administered to 15 (38%) patients and Cyclophosphamide to 14 (35%). Eighteen (45%) received azathioprine and 3 (8%) mycophenolate mofetil. Plasmapheresis was performed in 14 patients (35%). The average time from beginning of symptoms to treatment initiation was 119 days.

The mean follow-up was 1094 days.

At discharge the mean serum creatinine was 2,5 mg/dL, eGFR 23ml/min/m2 and none of the patients died.

At six months, mean serum creatinine was 1.6 mg/dL, eGFR 31ml/min/m2 but 15 (38%) patients were dialysis-dependent. Two relapses occurred and 17 (43%) had infections during this period. Five (13%) patients died.

At 12 months, mean serum creatinine was 2.0 mg/dL, eGFR 29 ml/min/m2 and (9) 23% patients were dialysis dependent. Six (30%) patients had infections and 5 (13%) died. In the end of follow up 13 (33%) patients had died.

On univariate analysis, hemoglobin (OR 0.59 [0.36-0.95], p = 0.031), uric acid (OR 1.85 [1.12-3.05], p = 0.027), hematuria (OR 1.00 [1.00-1.00], p = 0.013), hemodialysis performed during 1st hospital stay (OR 22.9 [2.3-217.9], p = 0.006) and plasmapheresis ( OR 12.0 [2.4-61.0], p = 0.003) were associated with RRT at six months.

Conclusion

RRT in AAV and anti-GBM disease has decreased over the last decades with the use of immunosuppressive therapies. Clinical presentation and plasmapheresis seem the major predictors for RRT.

Renal thrombotic microangiopathy in an ANCA-associated vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA) disease remains a diagnostic challenge due to the heterogeneity of possible clinical presentations. We present the case of a 63-year-old white male with a known history of ANCA-associated vasculitis (AAV) with anti-myeloperoxidase antibodies (MPO) – mainly with respiratory manifestations – treated with corticosteroids and cyclophosphamide, resulting in partial improvement. Six months later he was referred to the nephrology department for rapidly progressive renal failure and a kidney biopsy was performed, which showed several glomeruli globally sclerosed and others presenting fibrous crescents. Vascular involvement was also noted with several small arteries revealing endothelial swelling and entrapped erythrocytes within a fibrin thrombus. Immunofluorescence was negative. A high percentage of parenchymal fibrosis and no evidence of active extra-renal manifestations dictated no specific treatment. The patient is currently monitored in a low clearance nephrology consultation. Evidence of thrombotic microangiopathy (TMA) is an uncommon histological finding in kidney biopsies of patients with AAV, being associated with worst prognosis.

Morphological Indexes: Can They Predict Lupus Nephritis Outcomes? A Retrospective Study

INTRODUCTION

Lupus nephritis is a serious complication of systemic lupus erythematosus. Currently, therapy is guided by findings in the renal biopsy, following the International Society of Nephrology / Renal Pathology Society classification. Austin and Hill's histomorphological indexes are not routinely obtained. In this retrospective single-centre study, we aimed to analyze the importance and applicability of the different morphological indexes in predicting response to treatment and prognosis.

MATERIAL AND METHODS

Patients with kidney biopsy demonstrating lupus nephritis from the 2010 - 2016 period were included. We analyzed their demographic data, comorbidities, clinical presentation and laboratorial evaluation at the time of renal biopsy. We evaluated the following outcomes: clinical remission, renal function and proteinuria at end of follow-up. Histologic analysis was performed using the International Society of Nephrology / Renal Pathology Society classification and the morphological indexes described by Austin (Activity and Chronicity) and Hill. Univariate and multivariate statistical analysis was performed using STATA software.

RESULTS

We analyzed 46 biopsy-proven lupus nephritis cases, with a median follow-up of 31.9 (13.2 - 45.6) months. Based on biopsy findings, 35 patients were started on immunosuppressive therapy. We observed that Class IV patients had, at presentation, lower estimated glomerular filtration rate (67.3 vs 94.6 mL/min; p = 0.02), higher proteinuria (4.26 vs 2.37 g/24 hours; p = 0.02) and a non-significantly higher C3 consumption (58.9 vs 77.4 mg/dL; p = 0.06). We did not observe correlations between International Society of Nephrology / Renal Pathology Society classification and the outcomes at the end of follow-up. In contrast, both the Hill biopsy index and Austin's Chronicity index were correlated with renal function and proteinuria at the end of follow-up. Austin's Activity index correlated with the immunological findings (C3, C4 and anti-dsDNA) at presentation.

DISCUSSION

Because clinical activity poorly correlates with histologic activity, histological findings are fundamental when assessing patients with suspected lupus nephritis. The most recent International Society of Nephrology / Renal Pathology Society report supports the European League Against Rheumatism guidelines, encouraging the adoption of histomorphological indexes when evaluating lupus nephritis. Our data, showing a correlation between the renal outcomes and the indexes described by Austin and Hill, supports this view.

CONCLUSION

The histomorphological indexes in lupus nephritis are easily obtainable, can predict renal outcomes and may help in the management of such patients.

Morphologic patterns and treatment of transplant glomerulopathy: A retrospective analysis

Transplant glomerulopathy is mainly due to chronic antibody-mediated rejection and actually represents a major cause of long-term allograft failure. The lack of effective treatment remains a serious problem in transplantation. A retrospective and uni-center study was performed in 48 kidney allograft recipients with transplant glomerulopathy between January 2010 and December 2015. Median time for diagnosis was 7.1 (3.6-11.8) years post-transplant. Light microscopy showed severity of transplant glomerulopathy in the majority of patients (cg1=10.4%; cg2=20.8%; cg3=68.8%). Moderate microvascular inflammation was present in 56.3% (g+ptc≥2), and almost half of recipients (51.1%) were C4d positive in immunofluorescence. Female gender (P=.001), age (P=.043), renal dysfunction (P=.002), acute rejection episodes (P=.026), and anti-HLA class II antibodies (P=.004) were associated with kidney allograft failure. Treatment of transplant glomerulopathy was performed in 67.6% of patients. The histologic and laboratory features that led to a therapeutic intervention were score ptc (P=.021), C4d (P=.03), and the presence of anti-HLA antibodies (P=.029), whereas score ah (P=.005) was associated with conservative measure. The overall cumulative kidney allograft survival at 10 years was 75%. Treatment of transplant glomerulopathy was ineffective to improve long-term kidney allograft survival.

Chronic allograft dysfunction-is there a treatment?

BACKGROUND

The major causes of renal transplant loss are death and chronic allograft dysfunction (CAD). The aims of this study were to determine the incidence of CAD in our population and the relation between allograft survival and immunosuppressive regimens.

METHODS

We studied retrospectively 473 patients who received deceased donor kidney transplants with at least 1 allograft biopsy between January 1990 and May 2007. Clinical data included age, gender, biopsy data, and immunosuppression before and after kidney biopsy. Mean age was 45.4 +/- 12.7 years including 65% males with a mean follow-up of 6.7 +/- 4.5 years. CAD was observed in 177 of 473 biopsies: 48 patients showed interstitial fibrosis (IF); 101 chronic rejection (CR); 16 transplant glomerulopathy (TG); and 12, CR and TG. Mean follow-up since the discovery of the histologic feature was 60.5 +/- 50.5 months for IF; 38.3 +/- 40.8 for CR, and 18.2 +/- 19.2 for TG.

RESULTS

CAD, which was more common in younger patients (P = .03), correlated upon univariate and multivariate analysis with CKD stage 5d development (P < .001). Deposition of C4d in peritubular capillaries was more frequent among CAD patients (P = .004), an association with particular relevance to recipients with CR (P = .02) and TG (P < .001). When we analyzed CAD subpopulation, we observed a positive correlation between allograft survival and immunosuppression modification after biopsy. Substitution of sirolimus (40/177) was shown in univariate, multivariate and Cox regression analyses to be a renal protector (P < .002). Allograft survival was also correlated with initial mycophenolate mofetil versus azathioprine, (62/177) immunosuppression (P < .001).

CONCLUSION

CAD, a frequent histologic feature, may benefit from sirolimus conversion.

Specificity and sensitivity of screening for anti-HLA antibodies in kidney allograft dysfunction

BACKGROUND

Prospective testing for posttransplant circulating anti-HLA antibodies seems to be a critical noninvasive tool, but confirmatory data are lacking.

MATERIALS AND METHODS

Over the last 3 years, peritubular capillary (PTC) C4d deposition was prospectively sought by an immunofluorescence technique applied to frozen tissue in biopsies obtained for allograft dysfunction. Screening for circulating anti-HLA class I/II alloantibodies (AlloAb) by the flow cytometric test was performed simultaneously.

RESULTS

We evaluated 132 sets of biopsies and simultaneous serum samples. PTC C4d deposition was demonstrated in 15.9% (21/132) of biopsies. Circulating anti-HLA I/II AlloAb were detected in 25% (33/132) of serum samples. Employing receiver-operator characteristic (ROC) curves for all C4d-positive biopsies, screening for AlloAb showed a global specificity of 82% and sensitivity of 61.9%. When this analysis was restricted to biopsies obtained in the first month posttransplantation, the sensitivity increased to 81.8%, but the specificity decreased to 76.9%. After the first month posttransplantation, we observed sensitivity of 40.0% and a specificity of 86.4%. In the first month posttransplantation, all patients with a diagnosis of acute antibody-mediated rejection displayed circulating anti-HLA class I/II, but not always at the same time as the C4d-positive biopsy.

CONCLUSIONS

In the first month posttransplantation, prospective monitoring of anti-HLA antibodies may be useful. The high sensitivity allows the identification of patients at risk, affording an earlier diagnosis of antibody-mediated rejection. After the first month, the test can be used to evaluate allograft dysfunction episodes, since positivity is highly suggestive of an antibody-mediated process.