HLA sensitized patients are at risk for antibody-mediated rejection (ABMR). Our purpose was to evaluate the importance of early protocol biopsies. From Jul/2010 to Jun/2012, 101 sensitized patients defined as PRA>10% (class I and/or II by Flow-PRA) were transplanted at our institution. Out of them, 60 performed donor-specific antibodies (DSA) at transplant and a protocol-bx at day 7 (D7) and were included in this study. A second for cause indication biopsy (IB) was done at the physician's discretion in 18 patients without previous acute rejection (AR) diagnosis. DSA were analyzed by single antigen bead assays at the time of biopsies (classified according to Banff'09 criteria). Patients (pts) mean age was 48±12 years, 48 were female (80%), 45 first transplant (75%) and 42 (70%) received a kidney from deceased donor. 34 pts never presented AR episodes while 26 did. 20/26 (77%) of AR were diagnosed in the first 3 weeks after transplantation (median 13 days). Day 7 protocol biopsies (PB) showed AR in 12/26 (46%): 10 (85%) ABMR and 2 (15%) T-cell-mediated rejection (TCMR). The IB (n=18) done at a median of 11 days from the PB (range 3-112), showed AR in another 14 pts (56%): 10(71%) ABMR and 4 (29%) TCMR, as presented in Table 1.

Pre-Tx mean MFI in ABMR pts did not differ among PB: 6001 (1596-11181) vs IB 2304 (840-14600)(p=NS). It also did not differ at the time of biopsy (2823 vs. 2277 in PB vs IB, respectively; p=NS). Patients with early ABMR diagnosis at PB had a trend to higher long-term MDRD (49±12mL/min) compared to patients with ABMR at IB (41±11mL/min) and similar to the whole non-ABMR patients (50±17mL/min). In conclusion, protocol biopsy is useful to diagnosis ABMR as early as in the first week pos-Tx. Early recognition of ABMR allows earlier treatment and possibly better long-term graft function in sensitized patients.

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