Introduction: In adult recipients histological findings in surveillance biopsies at 1-year post kidney transplantation (KT) correlate independently with short and long-term graft survival. Donor specific antibodies (dnDSA) are associated with antibody- mediated rejection. Non-adherence (NOA) to treatment, is a risk factor for dnDSA. Studies in children with KT with protocol biopsies are scarce.
Objective: To evaluate the prevalence of favorable (FAV) and unfavorable (UNFAV) histological lesions (FAV) for graft survival in 1-year protocol biopsies of KT children and to identify risk variables for these lesions.
Methods: Prospective cohort study in all recipients of a 1st KT between 06/01/2018 and 05/30/2019. (TABLE 1) According to their histological risk, lesions were grouped in “FAV” and “UNFAV”. “FAV” lesions were: 1) minor morphological changes, with absence of inflammation and / or fibrosis and / or chronic glomerulopathy or glomerulonephritis, 2) Acute Interstitial inflammation without interstitial fibrosis or glomerular changes 3) Mild Interstitial fibrosis with absence of interstitial inflammation. “UNFAV” lesions were: 1) moderate-severe interstitial fibrosis without inflammation 2) acute or chronic active rejection mediated by antibodies or T cells 3) de novo glomerular disease 4) polyoma virus-associated nephropathy. dn-DSA were sought simultaneously with kidney biopsy. TAC and / or SRL variation coefficient (VC) >25% was considered a surrogate of NOA.
Results: 38 children were included. 29 had “FAV” lesions (76%): 23, Minimal morphological changes, and 6 mild fibrosis. Nine had “UNFAV” histology (24%): One had disease recurrence, three acute vascular rejection, (2/3 subclinical rejection; 1/3 DSA+) and four had moderate fibrosis (2 had graft hydronephrosis and 2 had previous AR,1DSA+). Mean eGFR in patients with “UNFAV” lesions was 39 ± 12.1 ml / min/ 1.73m2 vs 65.3 ± 18 ml / min / 1.73m2 in those with “FAV” (p=0.0003). Both groups had similar pre KT clinical and demographic characteristics. (TABLE2). UNFAV patients had higher incidence of previous Acute Rejection (TABLE2). TAC or SRL VC was: < 25% in 71% of patients (n= 27), and > 25% in 19% of patients (n=11), those with irregular intake. Children with VC> 25% had higher risk of an “UNFAV” lesion in protocol biopsy (OR: 4.8; p=0,04) and higher prevalence of dnDSA (18% vs 0%; p=0.02)
Conclusion: In this cohort, FAV lesions were the most prevalent and were associated with negative dnDSA and TAC or SRL VC <25%. Children with UNFAV lesions had lower eGFR. Those with TAC or SRL VC>25% had higher risk of an “UNFAV” lesion, and higher prevalence of dnDSA. Follow-up of this cohort is imperative.