Background: Interstitial fibrosis and tubular atrophy (IFTA) associated with interstitial inflammation in nonscarred areas (IFTA+i) is associated with poorer graft outcome than inflammation without IFTA or IFTA without inflammation.
Methods: We evaluated if histological categories at week 6 could predict the development of interstitial fibrosis and de novo donor specific anti-HLA antibodies (dnDSA) at 1 year. Biopsies were classified according to Banff criteria as normal (i+t≤1 and ci+ct≤1), inflammation (i+t≥2 and ci+ct≤1), IFTA (i+t≤1 and ci+ct≥2) or IFTA+i (i+t≥2 and ci+ct≥2).
Results: We analyzed 598 standard immunological risk recipients. The histological diagnosis at 6 weeks was: normal (n = 206), inflammation (n = 29), IFTA (n = 255), and IFTA+i (n = 108). Moderate/severe interstitial fibrosis (ci≥2) at 1 year was observed in 4.2% of patients with prior (6 weeks) normal histology, in 3.4% with inflammation, in 13.8% with IFTA, and in 24.5% with IFTA+i (P = 0.0001). Fifty-three recipients (8.9%) had dnDSA at 1 year. Independent predictors of development of dnDSA at 1 year were: HLA-DR mismatches (odds ratio [OR], 1.95; 95% confidence interval [95% CI], 1.09-3.49), the presence of inflammation (OR, 5.49; 95% CI, 1.67-18.03) or IFTA+i (OR, 4.09; 95% CI, 1.67-10.0) in the 6-week surveillance biopsy.
Conclusions: Early subclinical inflammation in surveillance biopsies with or without tubulointerstitial chronic lesions is associated with an increased risk of dnDSA development.