Surveillance biopsies [SBx] are not universally performed following renal transplantation. In patients in whom protocol biopsies are performed, how best to manage subclinical rejection [SCR] is not known. The aim of this study to determine the outcomes of treated SCR compared with a historic control group with untreated SCR.

We included 550 patients who underwent a SBx in the first year post-transplant. In a previous study we showed that 26 patients with untreated SCR [uSCR] had higher risk of clinical rejection than patients with no SCR on SBx, with a rejection free survival of 90.0% and 76.9% respectively, p=0.0078. Following this analysis a change in protocol was made at our centre and SCR is now treated conventionally with corticosteroids and MMF [tSCR]. We have subsequently treated 16 patients with SCR and in this study compare their clinical outcomes with our historic group of 26 patients with uSCR.

Allograft survival was 100.0% and 65.9% in the tSCR and uSCR groups respectively, p=0.62. Clinical rejection free survival was 83.3% in the tSCR and 58.8% in the uSCR groups, p=0.42. AMR free survival was 83.0% and 64.1%, p=0.83 and ACR free survival was 100.0% and 85.6%, p=0.19 in the tSCR and uSCR groups respectively. TG free survival was 100.0% and 55.6%, p=0.22 and de novo DSA free survival was 100.0% and 78.1%, p=0.35 in the tSCR and uSCR groups respectively. Histological features on follow up biopsies in 9/16 tSCR showed a decrease in g, c, t and C4d scores but an increase in c, cg and C4d scores was seen in the 20/28 uSCR group.

Although these data are preliminary and patient numbers are small, treatment of SCR results in better allograft survival, less rejection and histological improvement in repeat biopsies Longer follow up is required but this study suggests treating SCR may reduce the development of chronic alloimmune injury.

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