Early i-IFTA: Associated factors and impact on graft outcome.

Assessment of inflammation in scarred cortical parenchyma of kidney transplant (i-IFTA) is a criterion for chronic active T cell-mediated rejection (TCMR) and has mainly been explored in one-year protocol biopsies. We evaluated the factors, molecular profile, and one-year graft outcome associated with early i-IFTA. We included 101 kidney transplant biopsies performed within the first six months posttransplant (median=89 days), between 2009 and 2020. Interstitial inflammation Banff criteria were retrospectively re-evaluated, and diagnosis reclassification was performed according to the Banff 2022 classification. After re-evaluation, 85% of the biopsies presented no rejection, including 16% of biopsies from patients with delayed graft function, and 5% of biopsies with BK polyomavirus nephropathy. Eleven per cent (11%) of the biopsies presented histological TCMR. Delayed graft function was associated with i-IFTA severity (OR=2.78, 95% CI:1.01-7.68, <i>p</i>=0.049). The molecular profile obtained in 93 biopsies revealed that 86% presented a no-rejection profile and that a TCMR molecular profile tended to be more frequent in biopsies with i-IFTA2/3 compared with i-IFTA0/1 (17% vs. 4%, <i>p</i>=0.060). I-IFTA0/1 and 2/3 presented comparable one-year graft outcomes, including donor-specific antibodies (DSA), rejection occurrence, and graft function. In conclusion, early i-IFTA is an ambiguous and non-specific lesion that can be associated with ischemia/reperfusion injury, early BK nephropathy, or rejection.